[PATCH v15 00/13] seccomp_filter: syscall filtering using BPF

[PATCH v15 00/13] seccomp_filter: syscall filtering using BPF

[Will Drewry]

Please see prior revisions of this patch series for a high
level blurb.

This revision makes a number of refinements and tweaks. The biggest
change is a slight renumbering of the return codes which will break
existing code using this patch series.

I believe this patch is in good shape, and I don't see the need for
any more API changes at this point.  I plan to start using this revision
more extensively, and I'd certainly appreciate any testing.

Thanks!
will


Kees Cook (1):
  seccomp: remove duplicated failure logging

Will Drewry (12):
  sk_run_filter: add BPF_S_ANC_SECCOMP_LD_W
  net/compat.c,linux/filter.h: share compat_sock_fprog
  seccomp: kill the seccomp_t typedef
  arch/x86: add syscall_get_arch to syscall.h
  asm/syscall.h: add syscall_get_arch
  seccomp: add system call filtering using BPF
  seccomp: add SECCOMP_RET_ERRNO
  signal, x86: add SIGSYS info and make it synchronous.
  seccomp: Add SECCOMP_RET_TRAP
  ptrace,seccomp: Add PTRACE_SECCOMP support
  x86: Enable HAVE_ARCH_SECCOMP_FILTER
  Documentation: prctl/seccomp_filter

 Documentation/prctl/seccomp_filter.txt |  156 +++++++++++
 arch/Kconfig                           |   24 ++
 arch/x86/Kconfig                       |    1 +
 arch/x86/ia32/ia32_signal.c            |    4 +
 arch/x86/include/asm/ia32.h            |    6 +
 arch/x86/include/asm/syscall.h         |   23 ++
 arch/x86/kernel/ptrace.c               |    7 +-
 include/asm-generic/siginfo.h          |   22 ++
 include/asm-generic/syscall.h          |   14 +
 include/linux/Kbuild                   |    1 +
 include/linux/audit.h                  |    8 +-
 include/linux/filter.h                 |   12 +
 include/linux/ptrace.h                 |    7 +-
 include/linux/sched.h                  |    2 +-
 include/linux/seccomp.h                |  105 +++++++-
 kernel/auditsc.c                       |   10 +-
 kernel/fork.c                          |    3 +
 kernel/ptrace.c                        |    3 +
 kernel/seccomp.c                       |  446 ++++++++++++++++++++++++++++++--
 kernel/signal.c                        |    9 +-
 kernel/sys.c                           |    2 +-
 net/compat.c                           |    8 -
 net/core/filter.c                      |    6 +
 samples/Makefile                       |    2 +-
 samples/seccomp/Makefile               |   38 +++
 samples/seccomp/bpf-direct.c           |  176 +++++++++++++
 samples/seccomp/bpf-fancy.c            |  102 ++++++++
 samples/seccomp/bpf-helper.c           |   89 +++++++
 samples/seccomp/bpf-helper.h           |  238 +++++++++++++++++
 samples/seccomp/dropper.c              |   68 +++++
 30 files changed, 1538 insertions(+), 54 deletions(-)
 create mode 100644 Documentation/prctl/seccomp_filter.txt
 create mode 100644 samples/seccomp/Makefile
 create mode 100644 samples/seccomp/bpf-direct.c
 create mode 100644 samples/seccomp/bpf-fancy.c
 create mode 100644 samples/seccomp/bpf-helper.c
 create mode 100644 samples/seccomp/bpf-helper.h
 create mode 100644 samples/seccomp/dropper.c

-- 
1.7.5.4

[kernel-hardening] [PATCH v15 00/13] seccomp_filter: syscall filtering using BPF

[Will Drewry]

Please see prior revisions of this patch series for a high
level blurb.

This revision makes a number of refinements and tweaks. The biggest
change is a slight renumbering of the return codes which will break
existing code using this patch series.

I believe this patch is in good shape, and I don't see the need for
any more API changes at this point.  I plan to start using this revision
more extensively, and I'd certainly appreciate any testing.

Thanks!
will


Kees Cook (1):
  seccomp: remove duplicated failure logging

Will Drewry (12):
  sk_run_filter: add BPF_S_ANC_SECCOMP_LD_W
  net/compat.c,linux/filter.h: share compat_sock_fprog
  seccomp: kill the seccomp_t typedef
  arch/x86: add syscall_get_arch to syscall.h
  asm/syscall.h: add syscall_get_arch
  seccomp: add system call filtering using BPF
  seccomp: add SECCOMP_RET_ERRNO
  signal, x86: add SIGSYS info and make it synchronous.
  seccomp: Add SECCOMP_RET_TRAP
  ptrace,seccomp: Add PTRACE_SECCOMP support
  x86: Enable HAVE_ARCH_SECCOMP_FILTER
  Documentation: prctl/seccomp_filter

 Documentation/prctl/seccomp_filter.txt |  156 +++++++++++
 arch/Kconfig                           |   24 ++
 arch/x86/Kconfig                       |    1 +
 arch/x86/ia32/ia32_signal.c            |    4 +
 arch/x86/include/asm/ia32.h            |    6 +
 arch/x86/include/asm/syscall.h         |   23 ++
 arch/x86/kernel/ptrace.c               |    7 +-
 include/asm-generic/siginfo.h          |   22 ++
 include/asm-generic/syscall.h          |   14 +
 include/linux/Kbuild                   |    1 +
 include/linux/audit.h                  |    8 +-
 include/linux/filter.h                 |   12 +
 include/linux/ptrace.h                 |    7 +-
 include/linux/sched.h                  |    2 +-
 include/linux/seccomp.h                |  105 +++++++-
 kernel/auditsc.c                       |   10 +-
 kernel/fork.c                          |    3 +
 kernel/ptrace.c                        |    3 +
 kernel/seccomp.c                       |  446 ++++++++++++++++++++++++++++++--
 kernel/signal.c                        |    9 +-
 kernel/sys.c                           |    2 +-
 net/compat.c                           |    8 -
 net/core/filter.c                      |    6 +
 samples/Makefile                       |    2 +-
 samples/seccomp/Makefile               |   38 +++
 samples/seccomp/bpf-direct.c           |  176 +++++++++++++
 samples/seccomp/bpf-fancy.c            |  102 ++++++++
 samples/seccomp/bpf-helper.c           |   89 +++++++
 samples/seccomp/bpf-helper.h           |  238 +++++++++++++++++
 samples/seccomp/dropper.c              |   68 +++++
 30 files changed, 1538 insertions(+), 54 deletions(-)
 create mode 100644 Documentation/prctl/seccomp_filter.txt
 create mode 100644 samples/seccomp/Makefile
 create mode 100644 samples/seccomp/bpf-direct.c
 create mode 100644 samples/seccomp/bpf-fancy.c
 create mode 100644 samples/seccomp/bpf-helper.c
 create mode 100644 samples/seccomp/bpf-helper.h
 create mode 100644 samples/seccomp/dropper.c

-- 
1.7.5.4

[PATCH v15 01/13] sk_run_filter: add BPF_S_ANC_SECCOMP_LD_W

[Will Drewry]

Introduces a new BPF ancillary instruction that all LD calls will be
mapped through when skb_run_filter() is being used for seccomp BPF.  The
rewriting will be done using a secondary chk_filter function that is run
after skb_chk_filter.

The code change is guarded by CONFIG_SECCOMP_FILTER which is added,
along with the seccomp_bpf_load() function later in this series.

This is based on http://lkml.org/lkml/2012/3/2/141

v15: include seccomp.h explicitly for when seccomp_bpf_load exists.
v14: First cut using a single additional instruction
... v13: made bpf functions generic.

Suggested-by: Indan Zupancic <indan@nul.nu>
Signed-off-by: Will Drewry <wad@chromium.org>
---
 include/linux/filter.h |    1 +
 net/core/filter.c      |    6 ++++++
 2 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 8eeb205..aaa2e80 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -228,6 +228,7 @@ enum {
 	BPF_S_ANC_HATYPE,
 	BPF_S_ANC_RXHASH,
 	BPF_S_ANC_CPU,
+	BPF_S_ANC_SECCOMP_LD_W,
 };
 
 #endif /* __KERNEL__ */
diff --git a/net/core/filter.c b/net/core/filter.c
index 5dea452..d775edc 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -39,6 +39,7 @@
 #include <linux/filter.h>
 #include <linux/reciprocal_div.h>
 #include <linux/ratelimit.h>
+#include <linux/seccomp.h>
 
 /* No hurry in this branch */
 static void *__load_pointer(const struct sk_buff *skb, int k, unsigned int size)
@@ -350,6 +351,11 @@ load_b:
 				A = 0;
 			continue;
 		}
+#ifdef CONFIG_SECCOMP_FILTER
+		case BPF_S_ANC_SECCOMP_LD_W:
+			A = seccomp_bpf_load(fentry->k);
+			continue;
+#endif
 		default:
 			WARN_RATELIMIT(1, "Unknown code:%u jt:%u tf:%u k:%u\n",
 				       fentry->code, fentry->jt,
-- 
1.7.5.4

[kernel-hardening] [PATCH v15 01/13] sk_run_filter: add BPF_S_ANC_SECCOMP_LD_W

[Will Drewry]

Introduces a new BPF ancillary instruction that all LD calls will be
mapped through when skb_run_filter() is being used for seccomp BPF.  The
rewriting will be done using a secondary chk_filter function that is run
after skb_chk_filter.

The code change is guarded by CONFIG_SECCOMP_FILTER which is added,
along with the seccomp_bpf_load() function later in this series.

This is based on http://lkml.org/lkml/2012/3/2/141

v15: include seccomp.h explicitly for when seccomp_bpf_load exists.
v14: First cut using a single additional instruction
... v13: made bpf functions generic.

Suggested-by: Indan Zupancic <indan@nul.nu>
Signed-off-by: Will Drewry <wad@chromium.org>
---
 include/linux/filter.h |    1 +
 net/core/filter.c      |    6 ++++++
 2 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 8eeb205..aaa2e80 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -228,6 +228,7 @@ enum {
 	BPF_S_ANC_HATYPE,
 	BPF_S_ANC_RXHASH,
 	BPF_S_ANC_CPU,
+	BPF_S_ANC_SECCOMP_LD_W,
 };
 
 #endif /* __KERNEL__ */
diff --git a/net/core/filter.c b/net/core/filter.c
index 5dea452..d775edc 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -39,6 +39,7 @@
 #include <linux/filter.h>
 #include <linux/reciprocal_div.h>
 #include <linux/ratelimit.h>
+#include <linux/seccomp.h>
 
 /* No hurry in this branch */
 static void *__load_pointer(const struct sk_buff *skb, int k, unsigned int size)
@@ -350,6 +351,11 @@ load_b:
 				A = 0;
 			continue;
 		}
+#ifdef CONFIG_SECCOMP_FILTER
+		case BPF_S_ANC_SECCOMP_LD_W:
+			A = seccomp_bpf_load(fentry->k);
+			continue;
+#endif
 		default:
 			WARN_RATELIMIT(1, "Unknown code:%u jt:%u tf:%u k:%u\n",
 				       fentry->code, fentry->jt,
-- 
1.7.5.4

[PATCH v15 02/13] net/compat.c,linux/filter.h: share compat_sock_fprog

[Will Drewry]

Any other users of bpf_*_filter that take a struct sock_fprog from
userspace will need to be able to also accept a compat_sock_fprog
if the arch supports compat calls.  This change let's the existing
compat_sock_fprog be shared.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Will Drewry <wad@chromium.org>

v14: rebase/nochanges
v13: rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
v12: rebase on to linux-next
v11: introduction
---
 include/linux/filter.h |   11 +++++++++++
 net/compat.c           |    8 --------
 2 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/include/linux/filter.h b/include/linux/filter.h
index aaa2e80..f2e5315 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -10,6 +10,7 @@
 
 #ifdef __KERNEL__
 #include <linux/atomic.h>
+#include <linux/compat.h>
 #endif
 
 /*
@@ -132,6 +133,16 @@ struct sock_fprog {	/* Required for SO_ATTACH_FILTER. */
 
 #ifdef __KERNEL__
 
+#ifdef CONFIG_COMPAT
+/*
+ * A struct sock_filter is architecture independent.
+ */
+struct compat_sock_fprog {
+	u16		len;
+	compat_uptr_t	filter;		/* struct sock_filter * */
+};
+#endif
+
 struct sk_buff;
 struct sock;
 
diff --git a/net/compat.c b/net/compat.c
index 6def90e..c5c61c8 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -326,14 +326,6 @@ void scm_detach_fds_compat(struct msghdr *kmsg, struct scm_cookie *scm)
 	__scm_destroy(scm);
 }
 
-/*
- * A struct sock_filter is architecture independent.
- */
-struct compat_sock_fprog {
-	u16		len;
-	compat_uptr_t	filter;		/* struct sock_filter * */
-};
-
 static int do_set_attach_filter(struct socket *sock, int level, int optname,
 				char __user *optval, unsigned int optlen)
 {
-- 
1.7.5.4

[kernel-hardening] [PATCH v15 02/13] net/compat.c,linux/filter.h: share compat_sock_fprog

[Will Drewry]

Any other users of bpf_*_filter that take a struct sock_fprog from
userspace will need to be able to also accept a compat_sock_fprog
if the arch supports compat calls.  This change let's the existing
compat_sock_fprog be shared.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Will Drewry <wad@chromium.org>

v14: rebase/nochanges
v13: rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
v12: rebase on to linux-next
v11: introduction
---
 include/linux/filter.h |   11 +++++++++++
 net/compat.c           |    8 --------
 2 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/include/linux/filter.h b/include/linux/filter.h
index aaa2e80..f2e5315 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -10,6 +10,7 @@
 
 #ifdef __KERNEL__
 #include <linux/atomic.h>
+#include <linux/compat.h>
 #endif
 
 /*
@@ -132,6 +133,16 @@ struct sock_fprog {	/* Required for SO_ATTACH_FILTER. */
 
 #ifdef __KERNEL__
 
+#ifdef CONFIG_COMPAT
+/*
+ * A struct sock_filter is architecture independent.
+ */
+struct compat_sock_fprog {
+	u16		len;
+	compat_uptr_t	filter;		/* struct sock_filter * */
+};
+#endif
+
 struct sk_buff;
 struct sock;
 
diff --git a/net/compat.c b/net/compat.c
index 6def90e..c5c61c8 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -326,14 +326,6 @@ void scm_detach_fds_compat(struct msghdr *kmsg, struct scm_cookie *scm)
 	__scm_destroy(scm);
 }
 
-/*
- * A struct sock_filter is architecture independent.
- */
-struct compat_sock_fprog {
-	u16		len;
-	compat_uptr_t	filter;		/* struct sock_filter * */
-};
-
 static int do_set_attach_filter(struct socket *sock, int level, int optname,
 				char __user *optval, unsigned int optlen)
 {
-- 
1.7.5.4

[PATCH v15 03/13] seccomp: kill the seccomp_t typedef

[Will Drewry]

Replaces the seccomp_t typedef with struct seccomp to match modern
kernel style.

v14: rebase/nochanges
v13: rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
v12: rebase on to linux-next
v8-v11: no changes
v7: struct seccomp_struct -> struct seccomp
v6: original inclusion in this series.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Reviewed-by: James Morris <jmorris@namei.org>
Signed-off-by: Will Drewry <wad@chromium.org>
---
 include/linux/sched.h   |    2 +-
 include/linux/seccomp.h |   10 ++++++----
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 3bcde52..6311128 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1420,7 +1420,7 @@ struct task_struct {
 	uid_t loginuid;
 	unsigned int sessionid;
 #endif
-	seccomp_t seccomp;
+	struct seccomp seccomp;
 
 /* Thread group tracking */
    	u32 parent_exec_id;
diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
index cc7a4e9..d61f27f 100644
--- a/include/linux/seccomp.h
+++ b/include/linux/seccomp.h
@@ -7,7 +7,9 @@
 #include <linux/thread_info.h>
 #include <asm/seccomp.h>
 
-typedef struct { int mode; } seccomp_t;
+struct seccomp {
+	int mode;
+};
 
 extern void __secure_computing(int);
 static inline void secure_computing(int this_syscall)
@@ -19,7 +21,7 @@ static inline void secure_computing(int this_syscall)
 extern long prctl_get_seccomp(void);
 extern long prctl_set_seccomp(unsigned long);
 
-static inline int seccomp_mode(seccomp_t *s)
+static inline int seccomp_mode(struct seccomp *s)
 {
 	return s->mode;
 }
@@ -28,7 +30,7 @@ static inline int seccomp_mode(seccomp_t *s)
 
 #include <linux/errno.h>
 
-typedef struct { } seccomp_t;
+struct seccomp { };
 
 #define secure_computing(x) do { } while (0)
 
@@ -42,7 +44,7 @@ static inline long prctl_set_seccomp(unsigned long arg2)
 	return -EINVAL;
 }
 
-static inline int seccomp_mode(seccomp_t *s)
+static inline int seccomp_mode(struct seccomp *s)
 {
 	return 0;
 }
-- 
1.7.5.4

[kernel-hardening] [PATCH v15 03/13] seccomp: kill the seccomp_t typedef

[Will Drewry]

Replaces the seccomp_t typedef with struct seccomp to match modern
kernel style.

v14: rebase/nochanges
v13: rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
v12: rebase on to linux-next
v8-v11: no changes
v7: struct seccomp_struct -> struct seccomp
v6: original inclusion in this series.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Reviewed-by: James Morris <jmorris@namei.org>
Signed-off-by: Will Drewry <wad@chromium.org>
---
 include/linux/sched.h   |    2 +-
 include/linux/seccomp.h |   10 ++++++----
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 3bcde52..6311128 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1420,7 +1420,7 @@ struct task_struct {
 	uid_t loginuid;
 	unsigned int sessionid;
 #endif
-	seccomp_t seccomp;
+	struct seccomp seccomp;
 
 /* Thread group tracking */
    	u32 parent_exec_id;
diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
index cc7a4e9..d61f27f 100644
--- a/include/linux/seccomp.h
+++ b/include/linux/seccomp.h
@@ -7,7 +7,9 @@
 #include <linux/thread_info.h>
 #include <asm/seccomp.h>
 
-typedef struct { int mode; } seccomp_t;
+struct seccomp {
+	int mode;
+};
 
 extern void __secure_computing(int);
 static inline void secure_computing(int this_syscall)
@@ -19,7 +21,7 @@ static inline void secure_computing(int this_syscall)
 extern long prctl_get_seccomp(void);
 extern long prctl_set_seccomp(unsigned long);
 
-static inline int seccomp_mode(seccomp_t *s)
+static inline int seccomp_mode(struct seccomp *s)
 {
 	return s->mode;
 }
@@ -28,7 +30,7 @@ static inline int seccomp_mode(seccomp_t *s)
 
 #include <linux/errno.h>
 
-typedef struct { } seccomp_t;
+struct seccomp { };
 
 #define secure_computing(x) do { } while (0)
 
@@ -42,7 +44,7 @@ static inline long prctl_set_seccomp(unsigned long arg2)
 	return -EINVAL;
 }
 
-static inline int seccomp_mode(seccomp_t *s)
+static inline int seccomp_mode(struct seccomp *s)
 {
 	return 0;
 }
-- 
1.7.5.4

[PATCH v15 04/13] arch/x86: add syscall_get_arch to syscall.h

[Will Drewry]

Add syscall_get_arch() to export the current AUDIT_ARCH_* based on system call
entry path.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Will Drewry <wad@chromium.org>

v14: rebase/nochanges
v13: rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
---
 arch/x86/include/asm/syscall.h |   23 +++++++++++++++++++++++
 1 files changed, 23 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/syscall.h b/arch/x86/include/asm/syscall.h
index d962e56..1d713e4 100644
--- a/arch/x86/include/asm/syscall.h
+++ b/arch/x86/include/asm/syscall.h
@@ -13,6 +13,7 @@
 #ifndef _ASM_X86_SYSCALL_H
 #define _ASM_X86_SYSCALL_H
 
+#include <linux/audit.h>
 #include <linux/sched.h>
 #include <linux/err.h>
 #include <asm/asm-offsets.h>	/* For NR_syscalls */
@@ -87,6 +88,12 @@ static inline void syscall_set_arguments(struct task_struct *task,
 	memcpy(&regs->bx + i, args, n * sizeof(args[0]));
 }
 
+static inline int syscall_get_arch(struct task_struct *task,
+				   struct pt_regs *regs)
+{
+	return AUDIT_ARCH_I386;
+}
+
 #else	 /* CONFIG_X86_64 */
 
 static inline void syscall_get_arguments(struct task_struct *task,
@@ -211,6 +218,22 @@ static inline void syscall_set_arguments(struct task_struct *task,
 		}
 }
 
+static inline int syscall_get_arch(struct task_struct *task,
+				   struct pt_regs *regs)
+{
+#ifdef CONFIG_IA32_EMULATION
+	/*
+	 * TS_COMPAT is set for 32-bit syscall entries and then
+	 * remains set until we return to user mode.
+	 *
+	 * TIF_IA32 tasks should always have TS_COMPAT set at
+	 * system call time.
+	 */
+	if (task_thread_info(task)->status & TS_COMPAT)
+		return AUDIT_ARCH_I386;
+#endif
+	return AUDIT_ARCH_X86_64;
+}
 #endif	/* CONFIG_X86_32 */
 
 #endif	/* _ASM_X86_SYSCALL_H */
-- 
1.7.5.4

[kernel-hardening] [PATCH v15 04/13] arch/x86: add syscall_get_arch to syscall.h

[Will Drewry]

Add syscall_get_arch() to export the current AUDIT_ARCH_* based on system call
entry path.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Will Drewry <wad@chromium.org>

v14: rebase/nochanges
v13: rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
---
 arch/x86/include/asm/syscall.h |   23 +++++++++++++++++++++++
 1 files changed, 23 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/syscall.h b/arch/x86/include/asm/syscall.h
index d962e56..1d713e4 100644
--- a/arch/x86/include/asm/syscall.h
+++ b/arch/x86/include/asm/syscall.h
@@ -13,6 +13,7 @@
 #ifndef _ASM_X86_SYSCALL_H
 #define _ASM_X86_SYSCALL_H
 
+#include <linux/audit.h>
 #include <linux/sched.h>
 #include <linux/err.h>
 #include <asm/asm-offsets.h>	/* For NR_syscalls */
@@ -87,6 +88,12 @@ static inline void syscall_set_arguments(struct task_struct *task,
 	memcpy(&regs->bx + i, args, n * sizeof(args[0]));
 }
 
+static inline int syscall_get_arch(struct task_struct *task,
+				   struct pt_regs *regs)
+{
+	return AUDIT_ARCH_I386;
+}
+
 #else	 /* CONFIG_X86_64 */
 
 static inline void syscall_get_arguments(struct task_struct *task,
@@ -211,6 +218,22 @@ static inline void syscall_set_arguments(struct task_struct *task,
 		}
 }
 
+static inline int syscall_get_arch(struct task_struct *task,
+				   struct pt_regs *regs)
+{
+#ifdef CONFIG_IA32_EMULATION
+	/*
+	 * TS_COMPAT is set for 32-bit syscall entries and then
+	 * remains set until we return to user mode.
+	 *
+	 * TIF_IA32 tasks should always have TS_COMPAT set at
+	 * system call time.
+	 */
+	if (task_thread_info(task)->status & TS_COMPAT)
+		return AUDIT_ARCH_I386;
+#endif
+	return AUDIT_ARCH_X86_64;
+}
 #endif	/* CONFIG_X86_32 */
 
 #endif	/* _ASM_X86_SYSCALL_H */
-- 
1.7.5.4

[PATCH v15 05/13] asm/syscall.h: add syscall_get_arch

[Will Drewry]

Adds a stub for a function that will return the AUDIT_ARCH_*
value appropriate to the supplied task based on the system
call convention.

For audit's use, the value can generally be hard-coded at the
audit-site.  However, for other functionality not inlined into
syscall entry/exit, this makes that information available.
seccomp_filter is the first planned consumer and, as such,
the comment indicates a tie to HAVE_ARCH_SECCOMP_FILTER.  That
is probably an unneeded detail.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Suggested-by: Roland McGrath <mcgrathr@chromium.org>
Signed-off-by: Will Drewry <wad@chromium.org>

v14: rebase/nochanges
v13: rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
v12: rebase on to linux-next
v11: fixed improper return type
v10: introduced
---
 include/asm-generic/syscall.h |   14 ++++++++++++++
 1 files changed, 14 insertions(+), 0 deletions(-)

diff --git a/include/asm-generic/syscall.h b/include/asm-generic/syscall.h
index 5c122ae..a2c13dc 100644
--- a/include/asm-generic/syscall.h
+++ b/include/asm-generic/syscall.h
@@ -142,4 +142,18 @@ void syscall_set_arguments(struct task_struct *task, struct pt_regs *regs,
 			   unsigned int i, unsigned int n,
 			   const unsigned long *args);
 
+/**
+ * syscall_get_arch - return the AUDIT_ARCH for the current system call
+ * @task:	task of interest, must be in system call entry tracing
+ * @regs:	task_pt_regs() of @task
+ *
+ * Returns the AUDIT_ARCH_* based on the system call convention in use.
+ *
+ * It's only valid to call this when @task is stopped on entry to a system
+ * call, due to %TIF_SYSCALL_TRACE, %TIF_SYSCALL_AUDIT, or %TIF_SECCOMP.
+ *
+ * Note, at present this function is only required with
+ * CONFIG_HAVE_ARCH_SECCOMP_FILTER.
+ */
+int syscall_get_arch(struct task_struct *task, struct pt_regs *regs);
 #endif	/* _ASM_SYSCALL_H */
-- 
1.7.5.4

[kernel-hardening] [PATCH v15 05/13] asm/syscall.h: add syscall_get_arch

[Will Drewry]

Adds a stub for a function that will return the AUDIT_ARCH_*
value appropriate to the supplied task based on the system
call convention.

For audit's use, the value can generally be hard-coded at the
audit-site.  However, for other functionality not inlined into
syscall entry/exit, this makes that information available.
seccomp_filter is the first planned consumer and, as such,
the comment indicates a tie to HAVE_ARCH_SECCOMP_FILTER.  That
is probably an unneeded detail.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Suggested-by: Roland McGrath <mcgrathr@chromium.org>
Signed-off-by: Will Drewry <wad@chromium.org>

v14: rebase/nochanges
v13: rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
v12: rebase on to linux-next
v11: fixed improper return type
v10: introduced
---
 include/asm-generic/syscall.h |   14 ++++++++++++++
 1 files changed, 14 insertions(+), 0 deletions(-)

diff --git a/include/asm-generic/syscall.h b/include/asm-generic/syscall.h
index 5c122ae..a2c13dc 100644
--- a/include/asm-generic/syscall.h
+++ b/include/asm-generic/syscall.h
@@ -142,4 +142,18 @@ void syscall_set_arguments(struct task_struct *task, struct pt_regs *regs,
 			   unsigned int i, unsigned int n,
 			   const unsigned long *args);
 
+/**
+ * syscall_get_arch - return the AUDIT_ARCH for the current system call
+ * @task:	task of interest, must be in system call entry tracing
+ * @regs:	task_pt_regs() of @task
+ *
+ * Returns the AUDIT_ARCH_* based on the system call convention in use.
+ *
+ * It's only valid to call this when @task is stopped on entry to a system
+ * call, due to %TIF_SYSCALL_TRACE, %TIF_SYSCALL_AUDIT, or %TIF_SECCOMP.
+ *
+ * Note, at present this function is only required with
+ * CONFIG_HAVE_ARCH_SECCOMP_FILTER.
+ */
+int syscall_get_arch(struct task_struct *task, struct pt_regs *regs);
 #endif	/* _ASM_SYSCALL_H */
-- 
1.7.5.4

[PATCH v15 06/13] seccomp: add system call filtering using BPF

[Will Drewry]

[This patch depends on luto@mit.edu's no_new_privs patch:
   https://lkml.org/lkml/2012/1/30/264
 The whole series including Andrew's patches can be found here:
   https://github.com/redpig/linux/tree/seccomp
 Complete diff here:
   https://github.com/redpig/linux/compare/1dc65fed...seccomp
 A GPG signed tag 'seccomp/v14/posted' will be pushed shortly.
]

This patch adds support for seccomp mode 2.  Mode 2 introduces the
ability for unprivileged processes to install system call filtering
policy expressed in terms of a Berkeley Packet Filter (BPF) program.
This program will be evaluated in the kernel for each system call
the task makes and computes a result based on data in the format
of struct seccomp_data.

A filter program may be installed by calling:
  struct sock_fprog fprog = { ... };
  ...
  prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &fprog);

The return value of the filter program determines if the system call is
allowed to proceed or denied.  If the first filter program installed
allows prctl(2) calls, then the above call may be made repeatedly
by a task to further reduce its access to the kernel.  All attached
programs must be evaluated before a system call will be allowed to
proceed.

Filter programs will be inherited across fork/clone and execve.
However, if the task attaching the filter is unprivileged
(!CAP_SYS_ADMIN) the no_new_privs bit will be set on the task.  This
ensures that unprivileged tasks cannot attach filters that affect
privileged tasks (e.g., setuid binary).

There are a number of benefits to this approach. A few of which are
as follows:
- BPF has been exposed to userland for a long time
- BPF optimization (and JIT'ing) are well understood
- Userland already knows its ABI: system call numbers and desired
  arguments
- No time-of-check-time-of-use vulnerable data accesses are possible.
- system call arguments are loaded on access only to minimize copying
  required for system call policy decisions.

Mode 2 support is restricted to architectures that enable
HAVE_ARCH_SECCOMP_FILTER.  In this patch, the primary dependency is on
syscall_get_arguments().  The full desired scope of this feature will
add a few minor additional requirements expressed later in this series.
Based on discussion, SECCOMP_RET_ERRNO and SECCOMP_RET_TRACE seem to be
the desired additional functionality.

No architectures are enabled in this patch.

v15: - add a 4 instr penalty when counting a path to account for seccomp_filter
       size (indan@nul.nu)
     - drop the max insns to 256KB (indan@nul.nu)
     - return ENOMEM if the max insns limit has been hit (indan@nul.nu)
     - move IP checks after args (indan@nul.nu)
     - drop !user_filter check (indan@nul.nu)
     - only allow explicit bpf codes (indan@nul.nu)
     - exit_code -> exit_sig
v14: - put/get_seccomp_filter takes struct task_struct
       (indan@nul.nu,keescook@chromium.org)
     - adds seccomp_chk_filter and drops general bpf_run/chk_filter user
     - add seccomp_bpf_load for use by net/core/filter.c
     - lower max per-process/per-hierarchy: 1MB
     - moved nnp/capability check prior to allocation
       (all of the above: indan@nul.nu)
v13: - rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
v12: - added a maximum instruction count per path (indan@nul.nu,oleg@redhat.com)
     - removed copy_seccomp (keescook@chromium.org,indan@nul.nu)
     - reworded the prctl_set_seccomp comment (indan@nul.nu)
v11: - reorder struct seccomp_data to allow future args expansion (hpa@zytor.com)
     - style clean up, @compat dropped, compat_sock_fprog32 (indan@nul.nu)
     - do_exit(SIGSYS) (keescook@chromium.org, luto@mit.edu)
     - pare down Kconfig doc reference.
     - extra comment clean up
v10: - seccomp_data has changed again to be more aesthetically pleasing
       (hpa@zytor.com)
     - calling convention is noted in a new u32 field using syscall_get_arch.
       This allows for cross-calling convention tasks to use seccomp filters.
       (hpa@zytor.com)
     - lots of clean up (thanks, Indan!)
 v9: - n/a
 v8: - use bpf_chk_filter, bpf_run_filter. update load_fns
     - Lots of fixes courtesy of indan@nul.nu:
     -- fix up load behavior, compat fixups, and merge alloc code,
     -- renamed pc and dropped __packed, use bool compat.
     -- Added a hidden CONFIG_SECCOMP_FILTER to synthesize non-arch
        dependencies
 v7:  (massive overhaul thanks to Indan, others)
     - added CONFIG_HAVE_ARCH_SECCOMP_FILTER
     - merged into seccomp.c
     - minimal seccomp_filter.h
     - no config option (part of seccomp)
     - no new prctl
     - doesn't break seccomp on systems without asm/syscall.h
       (works but arg access always fails)
     - dropped seccomp_init_task, extra free functions, ...
     - dropped the no-asm/syscall.h code paths
     - merges with network sk_run_filter and sk_chk_filter
 v6: - fix memory leak on attach compat check failure
     - require no_new_privs || CAP_SYS_ADMIN prior to filter
       installation. (luto@mit.edu)
     - s/seccomp_struct_/seccomp_/ for macros/functions (amwang@redhat.com)
     - cleaned up Kconfig (amwang@redhat.com)
     - on block, note if the call was compat (so the # means something)
 v5: - uses syscall_get_arguments
       (indan@nul.nu,oleg@redhat.com, mcgrathr@chromium.org)
      - uses union-based arg storage with hi/lo struct to
        handle endianness.  Compromises between the two alternate
        proposals to minimize extra arg shuffling and account for
        endianness assuming userspace uses offsetof().
        (mcgrathr@chromium.org, indan@nul.nu)
      - update Kconfig description
      - add include/seccomp_filter.h and add its installation
      - (naive) on-demand syscall argument loading
      - drop seccomp_t (eparis@redhat.com)
 v4:  - adjusted prctl to make room for PR_[SG]ET_NO_NEW_PRIVS
      - now uses current->no_new_privs
        (luto@mit.edu,torvalds@linux-foundation.com)
      - assign names to seccomp modes (rdunlap@xenotime.net)
      - fix style issues (rdunlap@xenotime.net)
      - reworded Kconfig entry (rdunlap@xenotime.net)
 v3:  - macros to inline (oleg@redhat.com)
      - init_task behavior fixed (oleg@redhat.com)
      - drop creator entry and extra NULL check (oleg@redhat.com)
      - alloc returns -EINVAL on bad sizing (serge.hallyn@canonical.com)
      - adds tentative use of "always_unprivileged" as per
        torvalds@linux-foundation.org and luto@mit.edu
 v2:  - (patch 2 only)

Reviewed-by: Indan Zupancic <indan@nul.nu>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>

Signed-off-by: Will Drewry <wad@chromium.org>
---
 arch/Kconfig            |   17 ++
 include/linux/Kbuild    |    1 +
 include/linux/seccomp.h |   76 +++++++++-
 kernel/fork.c           |    3 +
 kernel/seccomp.c        |  391 ++++++++++++++++++++++++++++++++++++++++++++---
 kernel/sys.c            |    2 +-
 6 files changed, 467 insertions(+), 23 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 4f55c73..7c6bd48 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -199,4 +199,21 @@ config HAVE_CMPXCHG_LOCAL
 config HAVE_CMPXCHG_DOUBLE
 	bool
 
+config HAVE_ARCH_SECCOMP_FILTER
+	bool
+	help
+	  This symbol should be selected by an architecure if it provides
+	  asm/syscall.h, specifically syscall_get_arguments() and
+	  syscall_get_arch().
+
+config SECCOMP_FILTER
+	def_bool y
+	depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
+	help
+	  Enable tasks to build secure computing environments defined
+	  in terms of Berkeley Packet Filter programs which implement
+	  task-defined system call filtering polices.
+
+	  See Documentation/prctl/seccomp_filter.txt for details.
+
 source "kernel/gcov/Kconfig"
diff --git a/include/linux/Kbuild b/include/linux/Kbuild
index c94e717..d41ba12 100644
--- a/include/linux/Kbuild
+++ b/include/linux/Kbuild
@@ -330,6 +330,7 @@ header-y += scc.h
 header-y += sched.h
 header-y += screen_info.h
 header-y += sdla.h
+header-y += seccomp.h
 header-y += securebits.h
 header-y += selinux_netlink.h
 header-y += sem.h
diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
index d61f27f..ce980a8 100644
--- a/include/linux/seccomp.h
+++ b/include/linux/seccomp.h
@@ -1,14 +1,67 @@
 #ifndef _LINUX_SECCOMP_H
 #define _LINUX_SECCOMP_H
 
+#include <linux/compiler.h>
+#include <linux/types.h>
+
+
+/* Valid values for seccomp.mode and prctl(PR_SET_SECCOMP, <mode>) */
+#define SECCOMP_MODE_DISABLED	0 /* seccomp is not in use. */
+#define SECCOMP_MODE_STRICT	1 /* uses hard-coded filter. */
+#define SECCOMP_MODE_FILTER	2 /* uses user-supplied filter. */
+
+/*
+ * All BPF programs must return a 32-bit value.
+ * The bottom 16-bits are reserved for future use.
+ * The upper 16-bits are ordered from least permissive values to most.
+ *
+ * The ordering ensures that a min_t() over composed return values always
+ * selects the least permissive choice.
+ */
+#define SECCOMP_RET_KILL	0x00000000U /* kill the task immediately */
+#define SECCOMP_RET_ALLOW	0x7fff0000U /* allow */
+
+/* Masks for the return value sections. */
+#define SECCOMP_RET_ACTION	0xffff0000U
+#define SECCOMP_RET_DATA	0x0000ffffU
+
+/**
+ * struct seccomp_data - the format the BPF program executes over.
+ * @nr: the system call number
+ * @arch: indicates system call convention as an AUDIT_ARCH_* value
+ *        as defined in <linux/audit.h>.
+ * @instruction_pointer: at the time of the system call.
+ * @args: up to 6 system call arguments always stored as 64-bit values
+ *        regardless of the architecture.
+ */
+struct seccomp_data {
+	int nr;
+	__u32 arch;
+	__u64 instruction_pointer;
+	__u64 args[6];
+};
 
+#ifdef __KERNEL__
 #ifdef CONFIG_SECCOMP
 
 #include <linux/thread_info.h>
 #include <asm/seccomp.h>
 
+struct seccomp_filter;
+/**
+ * struct seccomp - the state of a seccomp'ed process
+ *
+ * @mode:  indicates one of the valid values above for controlled
+ *         system calls available to a process.
+ * @filter: The metadata and ruleset for determining what system calls
+ *          are allowed for a task.
+ *
+ *          @filter must only be accessed from the context of current as there
+ *          is no locking.
+ */
 struct seccomp {
 	int mode;
+	struct seccomp_filter *filter;
 };
 
 extern void __secure_computing(int);
@@ -19,7 +72,7 @@ static inline void secure_computing(int this_syscall)
 }
 
 extern long prctl_get_seccomp(void);
-extern long prctl_set_seccomp(unsigned long);
+extern long prctl_set_seccomp(unsigned long, char __user *);
 
 static inline int seccomp_mode(struct seccomp *s)
 {
@@ -31,15 +84,16 @@ static inline int seccomp_mode(struct seccomp *s)
 #include <linux/errno.h>
 
 struct seccomp { };
+struct seccomp_filter { };
 
-#define secure_computing(x) do { } while (0)
+#define secure_computing(x) 0
 
 static inline long prctl_get_seccomp(void)
 {
 	return -EINVAL;
 }
 
-static inline long prctl_set_seccomp(unsigned long arg2)
+static inline long prctl_set_seccomp(unsigned long arg2, char __user *arg3)
 {
 	return -EINVAL;
 }
@@ -48,7 +102,21 @@ static inline int seccomp_mode(struct seccomp *s)
 {
 	return 0;
 }
-
 #endif /* CONFIG_SECCOMP */
 
+#ifdef CONFIG_SECCOMP_FILTER
+extern void put_seccomp_filter(struct task_struct *tsk);
+extern void get_seccomp_filter(struct task_struct *tsk);
+extern u32 seccomp_bpf_load(int off);
+#else  /* CONFIG_SECCOMP_FILTER */
+static inline void put_seccomp_filter(struct task_struct *tsk)
+{
+	return;
+}
+static inline void get_seccomp_filter(struct task_struct *tsk)
+{
+	return;
+}
+#endif /* CONFIG_SECCOMP_FILTER */
+#endif /* __KERNEL__ */
 #endif /* _LINUX_SECCOMP_H */
diff --git a/kernel/fork.c b/kernel/fork.c
index 26a7a67..4f7a186 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -34,6 +34,7 @@
 #include <linux/cgroup.h>
 #include <linux/security.h>
 #include <linux/hugetlb.h>
+#include <linux/seccomp.h>
 #include <linux/swap.h>
 #include <linux/syscalls.h>
 #include <linux/jiffies.h>
@@ -170,6 +171,7 @@ void free_task(struct task_struct *tsk)
 	free_thread_info(tsk->stack);
 	rt_mutex_debug_task_free(tsk);
 	ftrace_graph_exit_task(tsk);
+	put_seccomp_filter(tsk);
 	free_task_struct(tsk);
 }
 EXPORT_SYMBOL(free_task);
@@ -1143,6 +1145,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 		goto fork_out;
 
 	ftrace_graph_init_task(p);
+	get_seccomp_filter(p);
 
 	rt_mutex_init_task(p);
 
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index e8d76c5..9e50174 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -3,16 +3,338 @@
  *
  * Copyright 2004-2005  Andrea Arcangeli <andrea@cpushare.com>
  *
- * This defines a simple but solid secure-computing mode.
+ * Copyright (C) 2012 Google, Inc.
+ * Will Drewry <wad@chromium.org>
+ *
+ * This defines a simple but solid secure-computing facility.
+ *
+ * Mode 1 uses a fixed list of allowed system calls.
+ * Mode 2 allows user-defined system call filters in the form
+ *        of Berkeley Packet Filters/Linux Socket Filters.
  */
 
+#include <linux/atomic.h>
 #include <linux/audit.h>
-#include <linux/seccomp.h>
-#include <linux/sched.h>
 #include <linux/compat.h>
+#include <linux/filter.h>
+#include <linux/sched.h>
+#include <linux/seccomp.h>
+#include <linux/security.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+
+#include <linux/tracehook.h>
+#include <asm/syscall.h>
 
 /* #define SECCOMP_DEBUG 1 */
-#define NR_SECCOMP_MODES 1
+
+#ifdef CONFIG_SECCOMP_FILTER
+/**
+ * struct seccomp_filter - container for seccomp BPF programs
+ *
+ * @usage: reference count to manage the object liftime.
+ *         get/put helpers should be used when accessing an instance
+ *         outside of a lifetime-guarded section.  In general, this
+ *         is only needed for handling filters shared across tasks.
+ * @prev: points to a previously installed, or inherited, filter
+ * @len: the number of instructions in the program
+ * @insns: the BPF program instructions to evaluate
+ *
+ * seccomp_filter objects are organized in a tree linked via the @prev
+ * pointer.  For any task, it appears to be a singly-linked list starting
+ * with current->seccomp.filter, the most recently attached or inherited filter.
+ * However, multiple filters may share a @prev node, by way of fork(), which
+ * results in a unidirectional tree existing in memory.  This is similar to
+ * how namespaces work.
+ *
+ * seccomp_filter objects should never be modified after being attached
+ * to a task_struct (other than @usage).
+ */
+struct seccomp_filter {
+	atomic_t usage;
+	struct seccomp_filter *prev;
+	unsigned short len;  /* Instruction count */
+	struct sock_filter insns[];
+};
+
+/* Limit any path through the tree to 256KB worth of instructions. */
+#define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter))
+
+static void seccomp_filter_log_failure(int syscall)
+{
+	int compat = 0;
+#ifdef CONFIG_COMPAT
+	compat = is_compat_task();
+#endif
+	pr_info("%s[%d]: %ssystem call %d blocked at 0x%lx\n",
+		current->comm, task_pid_nr(current),
+		(compat ? "compat " : ""),
+		syscall, KSTK_EIP(current));
+}
+
+/**
+ * get_u32 - returns a u32 offset into data
+ * @data: a unsigned 64 bit value
+ * @index: 0 or 1 to return the first or second 32-bits
+ *
+ * This inline exists to hide the length of unsigned long.
+ * If a 32-bit unsigned long is passed in, it will be extended
+ * and the top 32-bits will be 0. If it is a 64-bit unsigned
+ * long, then whatever data is resident will be properly returned.
+ */
+static inline u32 get_u32(u64 data, int index)
+{
+	return ((u32 *)&data)[index];
+}
+
+/* Helper for bpf_load below. */
+#define BPF_DATA(_name) offsetof(struct seccomp_data, _name)
+/**
+ * bpf_load: checks and returns a pointer to the requested offset
+ * @off: offset into struct seccomp_data to load from
+ *
+ * Returns the requested 32-bits of data.
+ * seccomp_chk_filter() should assure that @off is 32-bit aligned
+ * and not out of bounds.  Failure to do so is a BUG.
+ */
+u32 seccomp_bpf_load(int off)
+{
+	struct pt_regs *regs = task_pt_regs(current);
+	if (off == BPF_DATA(nr))
+		return syscall_get_nr(current, regs);
+	if (off == BPF_DATA(arch))
+		return syscall_get_arch(current, regs);
+	if (off >= BPF_DATA(args[0]) && off < BPF_DATA(args[6])) {
+		unsigned long value;
+		int arg = (off - BPF_DATA(args[0])) / sizeof(u64);
+		int index = !!(off % sizeof(u64));
+		syscall_get_arguments(current, regs, arg, 1, &value);
+		return get_u32(value, index);
+	}
+	if (off == BPF_DATA(instruction_pointer))
+		return get_u32(KSTK_EIP(current), 0);
+	if (off == BPF_DATA(instruction_pointer) + sizeof(u32))
+		return get_u32(KSTK_EIP(current), 1);
+	/* seccomp_chk_filter should make this impossible. */
+	BUG();
+}
+
+/**
+ *	seccomp_chk_filter - verify seccomp filter code
+ *	@filter: filter to verify
+ *	@flen: length of filter
+ *
+ * Takes a previously checked filter (by sk_chk_filter) and
+ * redirects all filter code that loads struct sk_buff data
+ * and related data through seccomp_bpf_load.  It also
+ * enforces length and alignment checking of those loads.
+ *
+ * Returns 0 if the rule set is legal or -EINVAL if not.
+ */
+static int seccomp_chk_filter(struct sock_filter *filter, unsigned int flen)
+{
+	int pc;
+	for (pc = 0; pc < flen; pc++) {
+		struct sock_filter *ftest = &filter[pc];
+		u16 code = ftest->code;
+		u32 k = ftest->k;
+		switch (code) {
+		case BPF_S_LD_W_ABS:
+			ftest->code = BPF_S_ANC_SECCOMP_LD_W;
+			/* 32-bit aligned and not out of bounds. */
+			if (k >= sizeof(struct seccomp_data) || k & 3)
+				return -EINVAL;
+			continue;
+		case BPF_S_LD_W_LEN:
+			ftest->code = BPF_S_LD_IMM;
+			ftest->k = sizeof(struct seccomp_data);
+			continue;
+		case BPF_S_LDX_W_LEN:
+			ftest->code = BPF_S_LDX_IMM;
+			ftest->k = sizeof(struct seccomp_data);
+			continue;
+		/* Explicitly include allowed calls. */
+		case BPF_S_RET_K:
+		case BPF_S_RET_A:
+		case BPF_S_ALU_ADD_K:
+		case BPF_S_ALU_ADD_X:
+		case BPF_S_ALU_SUB_K:
+		case BPF_S_ALU_SUB_X:
+		case BPF_S_ALU_MUL_K:
+		case BPF_S_ALU_MUL_X:
+		case BPF_S_ALU_DIV_X:
+		case BPF_S_ALU_AND_K:
+		case BPF_S_ALU_AND_X:
+		case BPF_S_ALU_OR_K:
+		case BPF_S_ALU_OR_X:
+		case BPF_S_ALU_LSH_K:
+		case BPF_S_ALU_LSH_X:
+		case BPF_S_ALU_RSH_K:
+		case BPF_S_ALU_RSH_X:
+		case BPF_S_ALU_NEG:
+		case BPF_S_LD_IMM:
+		case BPF_S_LDX_IMM:
+		case BPF_S_MISC_TAX:
+		case BPF_S_MISC_TXA:
+		case BPF_S_ALU_DIV_K:
+		case BPF_S_LD_MEM:
+		case BPF_S_LDX_MEM:
+		case BPF_S_ST:
+		case BPF_S_STX:
+		case BPF_S_JMP_JA:
+		case BPF_S_JMP_JEQ_K:
+		case BPF_S_JMP_JEQ_X:
+		case BPF_S_JMP_JGE_K:
+		case BPF_S_JMP_JGE_X:
+		case BPF_S_JMP_JGT_K:
+		case BPF_S_JMP_JGT_X:
+		case BPF_S_JMP_JSET_K:
+		case BPF_S_JMP_JSET_X:
+			continue;
+		default:
+			return -EINVAL;
+		}
+	}
+	return 0;
+}
+
+/**
+ * seccomp_run_filters - evaluates all seccomp filters against @syscall
+ * @syscall: number of the current system call
+ *
+ * Returns valid seccomp BPF response codes.
+ */
+static u32 seccomp_run_filters(int syscall)
+{
+	struct seccomp_filter *f;
+	u32 ret = SECCOMP_RET_KILL;
+	/*
+	 * All filters are evaluated in order of youngest to oldest. The lowest
+	 * BPF return value always takes priority.
+	 */
+	for (f = current->seccomp.filter; f; f = f->prev) {
+		ret = sk_run_filter(NULL, f->insns);
+		if (ret != SECCOMP_RET_ALLOW)
+			break;
+	}
+	return ret;
+}
+
+/**
+ * seccomp_attach_filter: Attaches a seccomp filter to current.
+ * @fprog: BPF program to install
+ *
+ * Returns 0 on success or an errno on failure.
+ */
+static long seccomp_attach_filter(struct sock_fprog *fprog)
+{
+	struct seccomp_filter *filter;
+	unsigned long fp_size = fprog->len * sizeof(struct sock_filter);
+	unsigned long total_insns = fprog->len;
+	long ret;
+
+	if (fprog->len == 0 || fprog->len > BPF_MAXINSNS)
+		return -EINVAL;
+
+	for (filter = current->seccomp.filter; filter; filter = filter->prev)
+		total_insns += filter->len + 4;  /* include a 4 instr penalty */
+	if (total_insns > MAX_INSNS_PER_PATH)
+		return -ENOMEM;
+
+	/*
+	 * Installing a seccomp filter requires that the task have
+	 * CAP_SYS_ADMIN in its namespace or be running with no_new_privs.
+	 * This avoids scenarios where unprivileged tasks can affect the
+	 * behavior of privileged children.
+	 */
+	if (!current->no_new_privs &&
+	    security_capable_noaudit(current_cred(), current_user_ns(),
+				     CAP_SYS_ADMIN) != 0)
+		return -EACCES;
+
+	/* Allocate a new seccomp_filter */
+	filter = kzalloc(sizeof(struct seccomp_filter) + fp_size, GFP_KERNEL);
+	if (!filter)
+		return -ENOMEM;
+	atomic_set(&filter->usage, 1);
+	filter->len = fprog->len;
+
+	/* Copy the instructions from fprog. */
+	ret = -EFAULT;
+	if (copy_from_user(filter->insns, fprog->filter, fp_size))
+		goto fail;
+
+	/* Check and rewrite the fprog via the skb checker */
+	ret = sk_chk_filter(filter->insns, filter->len);
+	if (ret)
+		goto fail;
+
+	/* Check and rewrite the fprog for seccomp use */
+	ret = seccomp_chk_filter(filter->insns, filter->len);
+	if (ret)
+		goto fail;
+
+	/*
+	 * If there is an existing filter, make it the prev and don't drop its
+	 * task reference.
+	 */
+	filter->prev = current->seccomp.filter;
+	current->seccomp.filter = filter;
+	return 0;
+fail:
+	kfree(filter);
+	return ret;
+}
+
+/**
+ * seccomp_attach_user_filter - attaches a user-supplied sock_fprog
+ * @user_filter: pointer to the user data containing a sock_fprog.
+ *
+ * Returns 0 on success and non-zero otherwise.
+ */
+long seccomp_attach_user_filter(char __user *user_filter)
+{
+	struct sock_fprog fprog;
+	long ret = -EFAULT;
+
+#ifdef CONFIG_COMPAT
+	if (is_compat_task()) {
+		struct compat_sock_fprog fprog32;
+		if (copy_from_user(&fprog32, user_filter, sizeof(fprog32)))
+			goto out;
+		fprog.len = fprog32.len;
+		fprog.filter = compat_ptr(fprog32.filter);
+	} else /* falls through to the if below. */
+#endif
+	if (copy_from_user(&fprog, user_filter, sizeof(fprog)))
+		goto out;
+	ret = seccomp_attach_filter(&fprog);
+out:
+	return ret;
+}
+
+/* get_seccomp_filter - increments the reference count of the filter on @tsk */
+void get_seccomp_filter(struct task_struct *tsk)
+{
+	struct seccomp_filter *orig = tsk->seccomp.filter;
+	if (!orig)
+		return;
+	/* Reference count is bounded by the number of total processes. */
+	atomic_inc(&orig->usage);
+}
+
+/* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */
+void put_seccomp_filter(struct task_struct *tsk)
+{
+	struct seccomp_filter *orig = tsk->seccomp.filter;
+	/* Clean up single-reference branches iteratively. */
+	while (orig && atomic_dec_and_test(&orig->usage)) {
+		struct seccomp_filter *freeme = orig;
+		orig = orig->prev;
+		kfree(freeme);
+	}
+}
+#endif	/* CONFIG_SECCOMP_FILTER */
 
 /*
  * Secure computing mode 1 allows only read/write/exit/sigreturn.
@@ -34,10 +356,11 @@ static int mode1_syscalls_32[] = {
 void __secure_computing(int this_syscall)
 {
 	int mode = current->seccomp.mode;
-	int * syscall;
+	int exit_sig = 0;
+	int *syscall;
 
 	switch (mode) {
-	case 1:
+	case SECCOMP_MODE_STRICT:
 		syscall = mode1_syscalls;
 #ifdef CONFIG_COMPAT
 		if (is_compat_task())
@@ -47,7 +370,16 @@ void __secure_computing(int this_syscall)
 			if (*syscall == this_syscall)
 				return;
 		} while (*++syscall);
+		exit_sig = SIGKILL;
+		break;
+#ifdef CONFIG_SECCOMP_FILTER
+	case SECCOMP_MODE_FILTER:
+		if (seccomp_run_filters(this_syscall) == SECCOMP_RET_ALLOW)
+			return;
+		seccomp_filter_log_failure(this_syscall);
+		exit_sig = SIGSYS;
 		break;
+#endif
 	default:
 		BUG();
 	}
@@ -56,7 +388,7 @@ void __secure_computing(int this_syscall)
 	dump_stack();
 #endif
 	audit_seccomp(this_syscall);
-	do_exit(SIGKILL);
+	do_exit(exit_sig);
 }
 
 long prctl_get_seccomp(void)
@@ -64,25 +396,48 @@ long prctl_get_seccomp(void)
 	return current->seccomp.mode;
 }
 
-long prctl_set_seccomp(unsigned long seccomp_mode)
+/**
+ * prctl_set_seccomp: configures current->seccomp.mode
+ * @seccomp_mode: requested mode to use
+ * @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER
+ *
+ * This function may be called repeatedly with a @seccomp_mode of
+ * SECCOMP_MODE_FILTER to install additional filters.  Every filter
+ * successfully installed will be evaluated (in reverse order) for each system
+ * call the task makes.
+ *
+ * Once current->seccomp.mode is non-zero, it may not be changed.
+ *
+ * Returns 0 on success or -EINVAL on failure.
+ */
+long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter)
 {
-	long ret;
+	long ret = -EINVAL;
 
-	/* can set it only once to be even more secure */
-	ret = -EPERM;
-	if (unlikely(current->seccomp.mode))
+	if (current->seccomp.mode &&
+	    current->seccomp.mode != seccomp_mode)
 		goto out;
 
-	ret = -EINVAL;
-	if (seccomp_mode && seccomp_mode <= NR_SECCOMP_MODES) {
-		current->seccomp.mode = seccomp_mode;
-		set_thread_flag(TIF_SECCOMP);
+	switch (seccomp_mode) {
+	case SECCOMP_MODE_STRICT:
+		ret = 0;
 #ifdef TIF_NOTSC
 		disable_TSC();
 #endif
-		ret = 0;
+		break;
+#ifdef CONFIG_SECCOMP_FILTER
+	case SECCOMP_MODE_FILTER:
+		ret = seccomp_attach_user_filter(filter);
+		if (ret)
+			goto out;
+		break;
+#endif
+	default:
+		goto out;
 	}
 
- out:
+	current->seccomp.mode = seccomp_mode;
+	set_thread_flag(TIF_SECCOMP);
+out:
 	return ret;
 }
diff --git a/kernel/sys.c b/kernel/sys.c
index 12e862a..038e6b7 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1899,7 +1899,7 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
 			error = prctl_get_seccomp();
 			break;
 		case PR_SET_SECCOMP:
-			error = prctl_set_seccomp(arg2);
+			error = prctl_set_seccomp(arg2, (char __user *)arg3);
 			break;
 		case PR_GET_TSC:
 			error = GET_TSC_CTL(arg2);
-- 
1.7.5.4

[kernel-hardening] [PATCH v15 06/13] seccomp: add system call filtering using BPF

[Will Drewry]

[This patch depends on luto@mit.edu's no_new_privs patch:
   https://lkml.org/lkml/2012/1/30/264
 The whole series including Andrew's patches can be found here:
   https://github.com/redpig/linux/tree/seccomp
 Complete diff here:
   https://github.com/redpig/linux/compare/1dc65fed...seccomp
 A GPG signed tag 'seccomp/v14/posted' will be pushed shortly.
]

This patch adds support for seccomp mode 2.  Mode 2 introduces the
ability for unprivileged processes to install system call filtering
policy expressed in terms of a Berkeley Packet Filter (BPF) program.
This program will be evaluated in the kernel for each system call
the task makes and computes a result based on data in the format
of struct seccomp_data.

A filter program may be installed by calling:
  struct sock_fprog fprog = { ... };
  ...
  prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &fprog);

The return value of the filter program determines if the system call is
allowed to proceed or denied.  If the first filter program installed
allows prctl(2) calls, then the above call may be made repeatedly
by a task to further reduce its access to the kernel.  All attached
programs must be evaluated before a system call will be allowed to
proceed.

Filter programs will be inherited across fork/clone and execve.
However, if the task attaching the filter is unprivileged
(!CAP_SYS_ADMIN) the no_new_privs bit will be set on the task.  This
ensures that unprivileged tasks cannot attach filters that affect
privileged tasks (e.g., setuid binary).

There are a number of benefits to this approach. A few of which are
as follows:
- BPF has been exposed to userland for a long time
- BPF optimization (and JIT'ing) are well understood
- Userland already knows its ABI: system call numbers and desired
  arguments
- No time-of-check-time-of-use vulnerable data accesses are possible.
- system call arguments are loaded on access only to minimize copying
  required for system call policy decisions.

Mode 2 support is restricted to architectures that enable
HAVE_ARCH_SECCOMP_FILTER.  In this patch, the primary dependency is on
syscall_get_arguments().  The full desired scope of this feature will
add a few minor additional requirements expressed later in this series.
Based on discussion, SECCOMP_RET_ERRNO and SECCOMP_RET_TRACE seem to be
the desired additional functionality.

No architectures are enabled in this patch.

v15: - add a 4 instr penalty when counting a path to account for seccomp_filter
       size (indan@nul.nu)
     - drop the max insns to 256KB (indan@nul.nu)
     - return ENOMEM if the max insns limit has been hit (indan@nul.nu)
     - move IP checks after args (indan@nul.nu)
     - drop !user_filter check (indan@nul.nu)
     - only allow explicit bpf codes (indan@nul.nu)
     - exit_code -> exit_sig
v14: - put/get_seccomp_filter takes struct task_struct
       (indan@nul.nu,keescook@chromium.org)
     - adds seccomp_chk_filter and drops general bpf_run/chk_filter user
     - add seccomp_bpf_load for use by net/core/filter.c
     - lower max per-process/per-hierarchy: 1MB
     - moved nnp/capability check prior to allocation
       (all of the above: indan@nul.nu)
v13: - rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
v12: - added a maximum instruction count per path (indan@nul.nu,oleg@redhat.com)
     - removed copy_seccomp (keescook@chromium.org,indan@nul.nu)
     - reworded the prctl_set_seccomp comment (indan@nul.nu)
v11: - reorder struct seccomp_data to allow future args expansion (hpa@zytor.com)
     - style clean up, @compat dropped, compat_sock_fprog32 (indan@nul.nu)
     - do_exit(SIGSYS) (keescook@chromium.org, luto@mit.edu)
     - pare down Kconfig doc reference.
     - extra comment clean up
v10: - seccomp_data has changed again to be more aesthetically pleasing
       (hpa@zytor.com)
     - calling convention is noted in a new u32 field using syscall_get_arch.
       This allows for cross-calling convention tasks to use seccomp filters.
       (hpa@zytor.com)
     - lots of clean up (thanks, Indan!)
 v9: - n/a
 v8: - use bpf_chk_filter, bpf_run_filter. update load_fns
     - Lots of fixes courtesy of indan@nul.nu:
     -- fix up load behavior, compat fixups, and merge alloc code,
     -- renamed pc and dropped __packed, use bool compat.
     -- Added a hidden CONFIG_SECCOMP_FILTER to synthesize non-arch
        dependencies
 v7:  (massive overhaul thanks to Indan, others)
     - added CONFIG_HAVE_ARCH_SECCOMP_FILTER
     - merged into seccomp.c
     - minimal seccomp_filter.h
     - no config option (part of seccomp)
     - no new prctl
     - doesn't break seccomp on systems without asm/syscall.h
       (works but arg access always fails)
     - dropped seccomp_init_task, extra free functions, ...
     - dropped the no-asm/syscall.h code paths
     - merges with network sk_run_filter and sk_chk_filter
 v6: - fix memory leak on attach compat check failure
     - require no_new_privs || CAP_SYS_ADMIN prior to filter
       installation. (luto@mit.edu)
     - s/seccomp_struct_/seccomp_/ for macros/functions (amwang@redhat.com)
     - cleaned up Kconfig (amwang@redhat.com)
     - on block, note if the call was compat (so the # means something)
 v5: - uses syscall_get_arguments
       (indan@nul.nu,oleg@redhat.com, mcgrathr@chromium.org)
      - uses union-based arg storage with hi/lo struct to
        handle endianness.  Compromises between the two alternate
        proposals to minimize extra arg shuffling and account for
        endianness assuming userspace uses offsetof().
        (mcgrathr@chromium.org, indan@nul.nu)
      - update Kconfig description
      - add include/seccomp_filter.h and add its installation
      - (naive) on-demand syscall argument loading
      - drop seccomp_t (eparis@redhat.com)
 v4:  - adjusted prctl to make room for PR_[SG]ET_NO_NEW_PRIVS
      - now uses current->no_new_privs
        (luto@mit.edu,torvalds@linux-foundation.com)
      - assign names to seccomp modes (rdunlap@xenotime.net)
      - fix style issues (rdunlap@xenotime.net)
      - reworded Kconfig entry (rdunlap@xenotime.net)
 v3:  - macros to inline (oleg@redhat.com)
      - init_task behavior fixed (oleg@redhat.com)
      - drop creator entry and extra NULL check (oleg@redhat.com)
      - alloc returns -EINVAL on bad sizing (serge.hallyn@canonical.com)
      - adds tentative use of "always_unprivileged" as per
        torvalds@linux-foundation.org and luto@mit.edu
 v2:  - (patch 2 only)

Reviewed-by: Indan Zupancic <indan@nul.nu>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>

Signed-off-by: Will Drewry <wad@chromium.org>
---
 arch/Kconfig            |   17 ++
 include/linux/Kbuild    |    1 +
 include/linux/seccomp.h |   76 +++++++++-
 kernel/fork.c           |    3 +
 kernel/seccomp.c        |  391 ++++++++++++++++++++++++++++++++++++++++++++---
 kernel/sys.c            |    2 +-
 6 files changed, 467 insertions(+), 23 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 4f55c73..7c6bd48 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -199,4 +199,21 @@ config HAVE_CMPXCHG_LOCAL
 config HAVE_CMPXCHG_DOUBLE
 	bool
 
+config HAVE_ARCH_SECCOMP_FILTER
+	bool
+	help
+	  This symbol should be selected by an architecure if it provides
+	  asm/syscall.h, specifically syscall_get_arguments() and
+	  syscall_get_arch().
+
+config SECCOMP_FILTER
+	def_bool y
+	depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
+	help
+	  Enable tasks to build secure computing environments defined
+	  in terms of Berkeley Packet Filter programs which implement
+	  task-defined system call filtering polices.
+
+	  See Documentation/prctl/seccomp_filter.txt for details.
+
 source "kernel/gcov/Kconfig"
diff --git a/include/linux/Kbuild b/include/linux/Kbuild
index c94e717..d41ba12 100644
--- a/include/linux/Kbuild
+++ b/include/linux/Kbuild
@@ -330,6 +330,7 @@ header-y += scc.h
 header-y += sched.h
 header-y += screen_info.h
 header-y += sdla.h
+header-y += seccomp.h
 header-y += securebits.h
 header-y += selinux_netlink.h
 header-y += sem.h
diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
index d61f27f..ce980a8 100644
--- a/include/linux/seccomp.h
+++ b/include/linux/seccomp.h
@@ -1,14 +1,67 @@
 #ifndef _LINUX_SECCOMP_H
 #define _LINUX_SECCOMP_H
 
+#include <linux/compiler.h>
+#include <linux/types.h>
+
+
+/* Valid values for seccomp.mode and prctl(PR_SET_SECCOMP, <mode>) */
+#define SECCOMP_MODE_DISABLED	0 /* seccomp is not in use. */
+#define SECCOMP_MODE_STRICT	1 /* uses hard-coded filter. */
+#define SECCOMP_MODE_FILTER	2 /* uses user-supplied filter. */
+
+/*
+ * All BPF programs must return a 32-bit value.
+ * The bottom 16-bits are reserved for future use.
+ * The upper 16-bits are ordered from least permissive values to most.
+ *
+ * The ordering ensures that a min_t() over composed return values always
+ * selects the least permissive choice.
+ */
+#define SECCOMP_RET_KILL	0x00000000U /* kill the task immediately */
+#define SECCOMP_RET_ALLOW	0x7fff0000U /* allow */
+
+/* Masks for the return value sections. */
+#define SECCOMP_RET_ACTION	0xffff0000U
+#define SECCOMP_RET_DATA	0x0000ffffU
+
+/**
+ * struct seccomp_data - the format the BPF program executes over.
+ * @nr: the system call number
+ * @arch: indicates system call convention as an AUDIT_ARCH_* value
+ *        as defined in <linux/audit.h>.
+ * @instruction_pointer: at the time of the system call.
+ * @args: up to 6 system call arguments always stored as 64-bit values
+ *        regardless of the architecture.
+ */
+struct seccomp_data {
+	int nr;
+	__u32 arch;
+	__u64 instruction_pointer;
+	__u64 args[6];
+};
 
+#ifdef __KERNEL__
 #ifdef CONFIG_SECCOMP
 
 #include <linux/thread_info.h>
 #include <asm/seccomp.h>
 
+struct seccomp_filter;
+/**
+ * struct seccomp - the state of a seccomp'ed process
+ *
+ * @mode:  indicates one of the valid values above for controlled
+ *         system calls available to a process.
+ * @filter: The metadata and ruleset for determining what system calls
+ *          are allowed for a task.
+ *
+ *          @filter must only be accessed from the context of current as there
+ *          is no locking.
+ */
 struct seccomp {
 	int mode;
+	struct seccomp_filter *filter;
 };
 
 extern void __secure_computing(int);
@@ -19,7 +72,7 @@ static inline void secure_computing(int this_syscall)
 }
 
 extern long prctl_get_seccomp(void);
-extern long prctl_set_seccomp(unsigned long);
+extern long prctl_set_seccomp(unsigned long, char __user *);
 
 static inline int seccomp_mode(struct seccomp *s)
 {
@@ -31,15 +84,16 @@ static inline int seccomp_mode(struct seccomp *s)
 #include <linux/errno.h>
 
 struct seccomp { };
+struct seccomp_filter { };
 
-#define secure_computing(x) do { } while (0)
+#define secure_computing(x) 0
 
 static inline long prctl_get_seccomp(void)
 {
 	return -EINVAL;
 }
 
-static inline long prctl_set_seccomp(unsigned long arg2)
+static inline long prctl_set_seccomp(unsigned long arg2, char __user *arg3)
 {
 	return -EINVAL;
 }
@@ -48,7 +102,21 @@ static inline int seccomp_mode(struct seccomp *s)
 {
 	return 0;
 }
-
 #endif /* CONFIG_SECCOMP */
 
+#ifdef CONFIG_SECCOMP_FILTER
+extern void put_seccomp_filter(struct task_struct *tsk);
+extern void get_seccomp_filter(struct task_struct *tsk);
+extern u32 seccomp_bpf_load(int off);
+#else  /* CONFIG_SECCOMP_FILTER */
+static inline void put_seccomp_filter(struct task_struct *tsk)
+{
+	return;
+}
+static inline void get_seccomp_filter(struct task_struct *tsk)
+{
+	return;
+}
+#endif /* CONFIG_SECCOMP_FILTER */
+#endif /* __KERNEL__ */
 #endif /* _LINUX_SECCOMP_H */
diff --git a/kernel/fork.c b/kernel/fork.c
index 26a7a67..4f7a186 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -34,6 +34,7 @@
 #include <linux/cgroup.h>
 #include <linux/security.h>
 #include <linux/hugetlb.h>
+#include <linux/seccomp.h>
 #include <linux/swap.h>
 #include <linux/syscalls.h>
 #include <linux/jiffies.h>
@@ -170,6 +171,7 @@ void free_task(struct task_struct *tsk)
 	free_thread_info(tsk->stack);
 	rt_mutex_debug_task_free(tsk);
 	ftrace_graph_exit_task(tsk);
+	put_seccomp_filter(tsk);
 	free_task_struct(tsk);
 }
 EXPORT_SYMBOL(free_task);
@@ -1143,6 +1145,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 		goto fork_out;
 
 	ftrace_graph_init_task(p);
+	get_seccomp_filter(p);
 
 	rt_mutex_init_task(p);
 
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index e8d76c5..9e50174 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -3,16 +3,338 @@
  *
  * Copyright 2004-2005  Andrea Arcangeli <andrea@cpushare.com>
  *
- * This defines a simple but solid secure-computing mode.
+ * Copyright (C) 2012 Google, Inc.
+ * Will Drewry <wad@chromium.org>
+ *
+ * This defines a simple but solid secure-computing facility.
+ *
+ * Mode 1 uses a fixed list of allowed system calls.
+ * Mode 2 allows user-defined system call filters in the form
+ *        of Berkeley Packet Filters/Linux Socket Filters.
  */
 
+#include <linux/atomic.h>
 #include <linux/audit.h>
-#include <linux/seccomp.h>
-#include <linux/sched.h>
 #include <linux/compat.h>
+#include <linux/filter.h>
+#include <linux/sched.h>
+#include <linux/seccomp.h>
+#include <linux/security.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+
+#include <linux/tracehook.h>
+#include <asm/syscall.h>
 
 /* #define SECCOMP_DEBUG 1 */
-#define NR_SECCOMP_MODES 1
+
+#ifdef CONFIG_SECCOMP_FILTER
+/**
+ * struct seccomp_filter - container for seccomp BPF programs
+ *
+ * @usage: reference count to manage the object liftime.
+ *         get/put helpers should be used when accessing an instance
+ *         outside of a lifetime-guarded section.  In general, this
+ *         is only needed for handling filters shared across tasks.
+ * @prev: points to a previously installed, or inherited, filter
+ * @len: the number of instructions in the program
+ * @insns: the BPF program instructions to evaluate
+ *
+ * seccomp_filter objects are organized in a tree linked via the @prev
+ * pointer.  For any task, it appears to be a singly-linked list starting
+ * with current->seccomp.filter, the most recently attached or inherited filter.
+ * However, multiple filters may share a @prev node, by way of fork(), which
+ * results in a unidirectional tree existing in memory.  This is similar to
+ * how namespaces work.
+ *
+ * seccomp_filter objects should never be modified after being attached
+ * to a task_struct (other than @usage).
+ */
+struct seccomp_filter {
+	atomic_t usage;
+	struct seccomp_filter *prev;
+	unsigned short len;  /* Instruction count */
+	struct sock_filter insns[];
+};
+
+/* Limit any path through the tree to 256KB worth of instructions. */
+#define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter))
+
+static void seccomp_filter_log_failure(int syscall)
+{
+	int compat = 0;
+#ifdef CONFIG_COMPAT
+	compat = is_compat_task();
+#endif
+	pr_info("%s[%d]: %ssystem call %d blocked at 0x%lx\n",
+		current->comm, task_pid_nr(current),
+		(compat ? "compat " : ""),
+		syscall, KSTK_EIP(current));
+}
+
+/**
+ * get_u32 - returns a u32 offset into data
+ * @data: a unsigned 64 bit value
+ * @index: 0 or 1 to return the first or second 32-bits
+ *
+ * This inline exists to hide the length of unsigned long.
+ * If a 32-bit unsigned long is passed in, it will be extended
+ * and the top 32-bits will be 0. If it is a 64-bit unsigned
+ * long, then whatever data is resident will be properly returned.
+ */
+static inline u32 get_u32(u64 data, int index)
+{
+	return ((u32 *)&data)[index];
+}
+
+/* Helper for bpf_load below. */
+#define BPF_DATA(_name) offsetof(struct seccomp_data, _name)
+/**
+ * bpf_load: checks and returns a pointer to the requested offset
+ * @off: offset into struct seccomp_data to load from
+ *
+ * Returns the requested 32-bits of data.
+ * seccomp_chk_filter() should assure that @off is 32-bit aligned
+ * and not out of bounds.  Failure to do so is a BUG.
+ */
+u32 seccomp_bpf_load(int off)
+{
+	struct pt_regs *regs = task_pt_regs(current);
+	if (off == BPF_DATA(nr))
+		return syscall_get_nr(current, regs);
+	if (off == BPF_DATA(arch))
+		return syscall_get_arch(current, regs);
+	if (off >= BPF_DATA(args[0]) && off < BPF_DATA(args[6])) {
+		unsigned long value;
+		int arg = (off - BPF_DATA(args[0])) / sizeof(u64);
+		int index = !!(off % sizeof(u64));
+		syscall_get_arguments(current, regs, arg, 1, &value);
+		return get_u32(value, index);
+	}
+	if (off == BPF_DATA(instruction_pointer))
+		return get_u32(KSTK_EIP(current), 0);
+	if (off == BPF_DATA(instruction_pointer) + sizeof(u32))
+		return get_u32(KSTK_EIP(current), 1);
+	/* seccomp_chk_filter should make this impossible. */
+	BUG();
+}
+
+/**
+ *	seccomp_chk_filter - verify seccomp filter code
+ *	@filter: filter to verify
+ *	@flen: length of filter
+ *
+ * Takes a previously checked filter (by sk_chk_filter) and
+ * redirects all filter code that loads struct sk_buff data
+ * and related data through seccomp_bpf_load.  It also
+ * enforces length and alignment checking of those loads.
+ *
+ * Returns 0 if the rule set is legal or -EINVAL if not.
+ */
+static int seccomp_chk_filter(struct sock_filter *filter, unsigned int flen)
+{
+	int pc;
+	for (pc = 0; pc < flen; pc++) {
+		struct sock_filter *ftest = &filter[pc];
+		u16 code = ftest->code;
+		u32 k = ftest->k;
+		switch (code) {
+		case BPF_S_LD_W_ABS:
+			ftest->code = BPF_S_ANC_SECCOMP_LD_W;
+			/* 32-bit aligned and not out of bounds. */
+			if (k >= sizeof(struct seccomp_data) || k & 3)
+				return -EINVAL;
+			continue;
+		case BPF_S_LD_W_LEN:
+			ftest->code = BPF_S_LD_IMM;
+			ftest->k = sizeof(struct seccomp_data);
+			continue;
+		case BPF_S_LDX_W_LEN:
+			ftest->code = BPF_S_LDX_IMM;
+			ftest->k = sizeof(struct seccomp_data);
+			continue;
+		/* Explicitly include allowed calls. */
+		case BPF_S_RET_K:
+		case BPF_S_RET_A:
+		case BPF_S_ALU_ADD_K:
+		case BPF_S_ALU_ADD_X:
+		case BPF_S_ALU_SUB_K:
+		case BPF_S_ALU_SUB_X:
+		case BPF_S_ALU_MUL_K:
+		case BPF_S_ALU_MUL_X:
+		case BPF_S_ALU_DIV_X:
+		case BPF_S_ALU_AND_K:
+		case BPF_S_ALU_AND_X:
+		case BPF_S_ALU_OR_K:
+		case BPF_S_ALU_OR_X:
+		case BPF_S_ALU_LSH_K:
+		case BPF_S_ALU_LSH_X:
+		case BPF_S_ALU_RSH_K:
+		case BPF_S_ALU_RSH_X:
+		case BPF_S_ALU_NEG:
+		case BPF_S_LD_IMM:
+		case BPF_S_LDX_IMM:
+		case BPF_S_MISC_TAX:
+		case BPF_S_MISC_TXA:
+		case BPF_S_ALU_DIV_K:
+		case BPF_S_LD_MEM:
+		case BPF_S_LDX_MEM:
+		case BPF_S_ST:
+		case BPF_S_STX:
+		case BPF_S_JMP_JA:
+		case BPF_S_JMP_JEQ_K:
+		case BPF_S_JMP_JEQ_X:
+		case BPF_S_JMP_JGE_K:
+		case BPF_S_JMP_JGE_X:
+		case BPF_S_JMP_JGT_K:
+		case BPF_S_JMP_JGT_X:
+		case BPF_S_JMP_JSET_K:
+		case BPF_S_JMP_JSET_X:
+			continue;
+		default:
+			return -EINVAL;
+		}
+	}
+	return 0;
+}
+
+/**
+ * seccomp_run_filters - evaluates all seccomp filters against @syscall
+ * @syscall: number of the current system call
+ *
+ * Returns valid seccomp BPF response codes.
+ */
+static u32 seccomp_run_filters(int syscall)
+{
+	struct seccomp_filter *f;
+	u32 ret = SECCOMP_RET_KILL;
+	/*
+	 * All filters are evaluated in order of youngest to oldest. The lowest
+	 * BPF return value always takes priority.
+	 */
+	for (f = current->seccomp.filter; f; f = f->prev) {
+		ret = sk_run_filter(NULL, f->insns);
+		if (ret != SECCOMP_RET_ALLOW)
+			break;
+	}
+	return ret;
+}
+
+/**
+ * seccomp_attach_filter: Attaches a seccomp filter to current.
+ * @fprog: BPF program to install
+ *
+ * Returns 0 on success or an errno on failure.
+ */
+static long seccomp_attach_filter(struct sock_fprog *fprog)
+{
+	struct seccomp_filter *filter;
+	unsigned long fp_size = fprog->len * sizeof(struct sock_filter);
+	unsigned long total_insns = fprog->len;
+	long ret;
+
+	if (fprog->len == 0 || fprog->len > BPF_MAXINSNS)
+		return -EINVAL;
+
+	for (filter = current->seccomp.filter; filter; filter = filter->prev)
+		total_insns += filter->len + 4;  /* include a 4 instr penalty */
+	if (total_insns > MAX_INSNS_PER_PATH)
+		return -ENOMEM;
+
+	/*
+	 * Installing a seccomp filter requires that the task have
+	 * CAP_SYS_ADMIN in its namespace or be running with no_new_privs.
+	 * This avoids scenarios where unprivileged tasks can affect the
+	 * behavior of privileged children.
+	 */
+	if (!current->no_new_privs &&
+	    security_capable_noaudit(current_cred(), current_user_ns(),
+				     CAP_SYS_ADMIN) != 0)
+		return -EACCES;
+
+	/* Allocate a new seccomp_filter */
+	filter = kzalloc(sizeof(struct seccomp_filter) + fp_size, GFP_KERNEL);
+	if (!filter)
+		return -ENOMEM;
+	atomic_set(&filter->usage, 1);
+	filter->len = fprog->len;
+
+	/* Copy the instructions from fprog. */
+	ret = -EFAULT;
+	if (copy_from_user(filter->insns, fprog->filter, fp_size))
+		goto fail;
+
+	/* Check and rewrite the fprog via the skb checker */
+	ret = sk_chk_filter(filter->insns, filter->len);
+	if (ret)
+		goto fail;
+
+	/* Check and rewrite the fprog for seccomp use */
+	ret = seccomp_chk_filter(filter->insns, filter->len);
+	if (ret)
+		goto fail;
+
+	/*
+	 * If there is an existing filter, make it the prev and don't drop its
+	 * task reference.
+	 */
+	filter->prev = current->seccomp.filter;
+	current->seccomp.filter = filter;
+	return 0;
+fail:
+	kfree(filter);
+	return ret;
+}
+
+/**
+ * seccomp_attach_user_filter - attaches a user-supplied sock_fprog
+ * @user_filter: pointer to the user data containing a sock_fprog.
+ *
+ * Returns 0 on success and non-zero otherwise.
+ */
+long seccomp_attach_user_filter(char __user *user_filter)
+{
+	struct sock_fprog fprog;
+	long ret = -EFAULT;
+
+#ifdef CONFIG_COMPAT
+	if (is_compat_task()) {
+		struct compat_sock_fprog fprog32;
+		if (copy_from_user(&fprog32, user_filter, sizeof(fprog32)))
+			goto out;
+		fprog.len = fprog32.len;
+		fprog.filter = compat_ptr(fprog32.filter);
+	} else /* falls through to the if below. */
+#endif
+	if (copy_from_user(&fprog, user_filter, sizeof(fprog)))
+		goto out;
+	ret = seccomp_attach_filter(&fprog);
+out:
+	return ret;
+}
+
+/* get_seccomp_filter - increments the reference count of the filter on @tsk */
+void get_seccomp_filter(struct task_struct *tsk)
+{
+	struct seccomp_filter *orig = tsk->seccomp.filter;
+	if (!orig)
+		return;
+	/* Reference count is bounded by the number of total processes. */
+	atomic_inc(&orig->usage);
+}
+
+/* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */
+void put_seccomp_filter(struct task_struct *tsk)
+{
+	struct seccomp_filter *orig = tsk->seccomp.filter;
+	/* Clean up single-reference branches iteratively. */
+	while (orig && atomic_dec_and_test(&orig->usage)) {
+		struct seccomp_filter *freeme = orig;
+		orig = orig->prev;
+		kfree(freeme);
+	}
+}
+#endif	/* CONFIG_SECCOMP_FILTER */
 
 /*
  * Secure computing mode 1 allows only read/write/exit/sigreturn.
@@ -34,10 +356,11 @@ static int mode1_syscalls_32[] = {
 void __secure_computing(int this_syscall)
 {
 	int mode = current->seccomp.mode;
-	int * syscall;
+	int exit_sig = 0;
+	int *syscall;
 
 	switch (mode) {
-	case 1:
+	case SECCOMP_MODE_STRICT:
 		syscall = mode1_syscalls;
 #ifdef CONFIG_COMPAT
 		if (is_compat_task())
@@ -47,7 +370,16 @@ void __secure_computing(int this_syscall)
 			if (*syscall == this_syscall)
 				return;
 		} while (*++syscall);
+		exit_sig = SIGKILL;
+		break;
+#ifdef CONFIG_SECCOMP_FILTER
+	case SECCOMP_MODE_FILTER:
+		if (seccomp_run_filters(this_syscall) == SECCOMP_RET_ALLOW)
+			return;
+		seccomp_filter_log_failure(this_syscall);
+		exit_sig = SIGSYS;
 		break;
+#endif
 	default:
 		BUG();
 	}
@@ -56,7 +388,7 @@ void __secure_computing(int this_syscall)
 	dump_stack();
 #endif
 	audit_seccomp(this_syscall);
-	do_exit(SIGKILL);
+	do_exit(exit_sig);
 }
 
 long prctl_get_seccomp(void)
@@ -64,25 +396,48 @@ long prctl_get_seccomp(void)
 	return current->seccomp.mode;
 }
 
-long prctl_set_seccomp(unsigned long seccomp_mode)
+/**
+ * prctl_set_seccomp: configures current->seccomp.mode
+ * @seccomp_mode: requested mode to use
+ * @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER
+ *
+ * This function may be called repeatedly with a @seccomp_mode of
+ * SECCOMP_MODE_FILTER to install additional filters.  Every filter
+ * successfully installed will be evaluated (in reverse order) for each system
+ * call the task makes.
+ *
+ * Once current->seccomp.mode is non-zero, it may not be changed.
+ *
+ * Returns 0 on success or -EINVAL on failure.
+ */
+long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter)
 {
-	long ret;
+	long ret = -EINVAL;
 
-	/* can set it only once to be even more secure */
-	ret = -EPERM;
-	if (unlikely(current->seccomp.mode))
+	if (current->seccomp.mode &&
+	    current->seccomp.mode != seccomp_mode)
 		goto out;
 
-	ret = -EINVAL;
-	if (seccomp_mode && seccomp_mode <= NR_SECCOMP_MODES) {
-		current->seccomp.mode = seccomp_mode;
-		set_thread_flag(TIF_SECCOMP);
+	switch (seccomp_mode) {
+	case SECCOMP_MODE_STRICT:
+		ret = 0;
 #ifdef TIF_NOTSC
 		disable_TSC();
 #endif
-		ret = 0;
+		break;
+#ifdef CONFIG_SECCOMP_FILTER
+	case SECCOMP_MODE_FILTER:
+		ret = seccomp_attach_user_filter(filter);
+		if (ret)
+			goto out;
+		break;
+#endif
+	default:
+		goto out;
 	}
 
- out:
+	current->seccomp.mode = seccomp_mode;
+	set_thread_flag(TIF_SECCOMP);
+out:
 	return ret;
 }
diff --git a/kernel/sys.c b/kernel/sys.c
index 12e862a..038e6b7 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1899,7 +1899,7 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
 			error = prctl_get_seccomp();
 			break;
 		case PR_SET_SECCOMP:
-			error = prctl_set_seccomp(arg2);
+			error = prctl_set_seccomp(arg2, (char __user *)arg3);
 			break;
 		case PR_GET_TSC:
 			error = GET_TSC_CTL(arg2);
-- 
1.7.5.4

[PATCH v15 07/13] seccomp: remove duplicated failure logging

[Will Drewry]

From: Kees Cook <keescook@chromium.org>

This consolidates the seccomp filter error logging path and adds more
details to the audit log.

Signed-off-by: Will Drewry <wad@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>

v15: added a return code to the audit_seccomp path by wad@chromium.org
     (suggested by eparis@redhat.com)
v*: original by keescook@chromium.org
---
 include/linux/audit.h |    8 ++++----
 kernel/auditsc.c      |   10 ++++++++--
 kernel/seccomp.c      |   15 +--------------
 3 files changed, 13 insertions(+), 20 deletions(-)

diff --git a/include/linux/audit.h b/include/linux/audit.h
index 9ff7a2c..1b95270 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -463,7 +463,7 @@ extern void audit_putname(const char *name);
 extern void __audit_inode(const char *name, const struct dentry *dentry);
 extern void __audit_inode_child(const struct dentry *dentry,
 				const struct inode *parent);
-extern void __audit_seccomp(unsigned long syscall);
+extern void __audit_seccomp(unsigned long syscall, long signr, int code);
 extern void __audit_ptrace(struct task_struct *t);
 
 static inline int audit_dummy_context(void)
@@ -508,10 +508,10 @@ static inline void audit_inode_child(const struct dentry *dentry,
 }
 void audit_core_dumps(long signr);
 
-static inline void audit_seccomp(unsigned long syscall)
+static inline void audit_seccomp(unsigned long syscall, long signr, int code)
 {
 	if (unlikely(!audit_dummy_context()))
-		__audit_seccomp(syscall);
+		__audit_seccomp(syscall, signr, code);
 }
 
 static inline void audit_ptrace(struct task_struct *t)
@@ -634,7 +634,7 @@ extern int audit_signals;
 #define audit_inode(n,d) do { (void)(d); } while (0)
 #define audit_inode_child(i,p) do { ; } while (0)
 #define audit_core_dumps(i) do { ; } while (0)
-#define audit_seccomp(i) do { ; } while (0)
+#define audit_seccomp(i,s,c) do { ; } while (0)
 #define auditsc_get_stamp(c,t,s) (0)
 #define audit_get_loginuid(t) (-1)
 #define audit_get_sessionid(t) (-1)
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index af1de0f..10dc528 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -67,6 +67,7 @@
 #include <linux/syscalls.h>
 #include <linux/capability.h>
 #include <linux/fs_struct.h>
+#include <linux/compat.h>
 
 #include "audit.h"
 
@@ -2710,13 +2711,18 @@ void audit_core_dumps(long signr)
 	audit_log_end(ab);
 }
 
-void __audit_seccomp(unsigned long syscall)
+void __audit_seccomp(unsigned long syscall, long signr, int code)
 {
 	struct audit_buffer *ab;
 
 	ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_ANOM_ABEND);
-	audit_log_abend(ab, "seccomp", SIGKILL);
+	audit_log_abend(ab, "seccomp", signr);
 	audit_log_format(ab, " syscall=%ld", syscall);
+#ifdef CONFIG_COMPAT
+	audit_log_format(ab, " compat=%d", is_compat_task());
+#endif
+	audit_log_format(ab, " ip=0x%lx", KSTK_EIP(current));
+	audit_log_format(ab, " code=0x%x", code);
 	audit_log_end(ab);
 }
 
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 9e50174..51c3462 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -60,18 +60,6 @@ struct seccomp_filter {
 /* Limit any path through the tree to 256KB worth of instructions. */
 #define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter))
 
-static void seccomp_filter_log_failure(int syscall)
-{
-	int compat = 0;
-#ifdef CONFIG_COMPAT
-	compat = is_compat_task();
-#endif
-	pr_info("%s[%d]: %ssystem call %d blocked at 0x%lx\n",
-		current->comm, task_pid_nr(current),
-		(compat ? "compat " : ""),
-		syscall, KSTK_EIP(current));
-}
-
 /**
  * get_u32 - returns a u32 offset into data
  * @data: a unsigned 64 bit value
@@ -376,7 +364,6 @@ void __secure_computing(int this_syscall)
 	case SECCOMP_MODE_FILTER:
 		if (seccomp_run_filters(this_syscall) == SECCOMP_RET_ALLOW)
 			return;
-		seccomp_filter_log_failure(this_syscall);
 		exit_sig = SIGSYS;
 		break;
 #endif
@@ -387,7 +374,7 @@ void __secure_computing(int this_syscall)
 #ifdef SECCOMP_DEBUG
 	dump_stack();
 #endif
-	audit_seccomp(this_syscall);
+	audit_seccomp(this_syscall, exit_code, SECCOMP_RET_KILL);
 	do_exit(exit_sig);
 }
 
-- 
1.7.5.4

[kernel-hardening] [PATCH v15 07/13] seccomp: remove duplicated failure logging

[Will Drewry]

From: Kees Cook <keescook@chromium.org>

This consolidates the seccomp filter error logging path and adds more
details to the audit log.

Signed-off-by: Will Drewry <wad@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>

v15: added a return code to the audit_seccomp path by wad@chromium.org
     (suggested by eparis@redhat.com)
v*: original by keescook@chromium.org
---
 include/linux/audit.h |    8 ++++----
 kernel/auditsc.c      |   10 ++++++++--
 kernel/seccomp.c      |   15 +--------------
 3 files changed, 13 insertions(+), 20 deletions(-)

diff --git a/include/linux/audit.h b/include/linux/audit.h
index 9ff7a2c..1b95270 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -463,7 +463,7 @@ extern void audit_putname(const char *name);
 extern void __audit_inode(const char *name, const struct dentry *dentry);
 extern void __audit_inode_child(const struct dentry *dentry,
 				const struct inode *parent);
-extern void __audit_seccomp(unsigned long syscall);
+extern void __audit_seccomp(unsigned long syscall, long signr, int code);
 extern void __audit_ptrace(struct task_struct *t);
 
 static inline int audit_dummy_context(void)
@@ -508,10 +508,10 @@ static inline void audit_inode_child(const struct dentry *dentry,
 }
 void audit_core_dumps(long signr);
 
-static inline void audit_seccomp(unsigned long syscall)
+static inline void audit_seccomp(unsigned long syscall, long signr, int code)
 {
 	if (unlikely(!audit_dummy_context()))
-		__audit_seccomp(syscall);
+		__audit_seccomp(syscall, signr, code);
 }
 
 static inline void audit_ptrace(struct task_struct *t)
@@ -634,7 +634,7 @@ extern int audit_signals;
 #define audit_inode(n,d) do { (void)(d); } while (0)
 #define audit_inode_child(i,p) do { ; } while (0)
 #define audit_core_dumps(i) do { ; } while (0)
-#define audit_seccomp(i) do { ; } while (0)
+#define audit_seccomp(i,s,c) do { ; } while (0)
 #define auditsc_get_stamp(c,t,s) (0)
 #define audit_get_loginuid(t) (-1)
 #define audit_get_sessionid(t) (-1)
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index af1de0f..10dc528 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -67,6 +67,7 @@
 #include <linux/syscalls.h>
 #include <linux/capability.h>
 #include <linux/fs_struct.h>
+#include <linux/compat.h>
 
 #include "audit.h"
 
@@ -2710,13 +2711,18 @@ void audit_core_dumps(long signr)
 	audit_log_end(ab);
 }
 
-void __audit_seccomp(unsigned long syscall)
+void __audit_seccomp(unsigned long syscall, long signr, int code)
 {
 	struct audit_buffer *ab;
 
 	ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_ANOM_ABEND);
-	audit_log_abend(ab, "seccomp", SIGKILL);
+	audit_log_abend(ab, "seccomp", signr);
 	audit_log_format(ab, " syscall=%ld", syscall);
+#ifdef CONFIG_COMPAT
+	audit_log_format(ab, " compat=%d", is_compat_task());
+#endif
+	audit_log_format(ab, " ip=0x%lx", KSTK_EIP(current));
+	audit_log_format(ab, " code=0x%x", code);
 	audit_log_end(ab);
 }
 
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 9e50174..51c3462 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -60,18 +60,6 @@ struct seccomp_filter {
 /* Limit any path through the tree to 256KB worth of instructions. */
 #define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter))
 
-static void seccomp_filter_log_failure(int syscall)
-{
-	int compat = 0;
-#ifdef CONFIG_COMPAT
-	compat = is_compat_task();
-#endif
-	pr_info("%s[%d]: %ssystem call %d blocked at 0x%lx\n",
-		current->comm, task_pid_nr(current),
-		(compat ? "compat " : ""),
-		syscall, KSTK_EIP(current));
-}
-
 /**
  * get_u32 - returns a u32 offset into data
  * @data: a unsigned 64 bit value
@@ -376,7 +364,6 @@ void __secure_computing(int this_syscall)
 	case SECCOMP_MODE_FILTER:
 		if (seccomp_run_filters(this_syscall) == SECCOMP_RET_ALLOW)
 			return;
-		seccomp_filter_log_failure(this_syscall);
 		exit_sig = SIGSYS;
 		break;
 #endif
@@ -387,7 +374,7 @@ void __secure_computing(int this_syscall)
 #ifdef SECCOMP_DEBUG
 	dump_stack();
 #endif
-	audit_seccomp(this_syscall);
+	audit_seccomp(this_syscall, exit_code, SECCOMP_RET_KILL);
 	do_exit(exit_sig);
 }
 
-- 
1.7.5.4

[PATCH v15 08/13] seccomp: add SECCOMP_RET_ERRNO

[Will Drewry]

This change adds the SECCOMP_RET_ERRNO as a valid return value from a
seccomp filter.  Additionally, it makes the first use of the lower
16-bits for storing a filter-supplied errno.  16-bits is more than
enough for the errno-base.h calls.

Returning errors instead of immediately terminating processes that
violate seccomp policy allow for broader use of this functionality
for kernel attack surface reduction.  For example, a linux container
could maintain a whitelist of pre-existing system calls but drop
all new ones with errnos.  This would keep a logically static attack
surface while providing errnos that may allow for graceful failure
without the downside of do_exit() on a bad call.

v15: - use audit_seccomp and add a skip label. (eparis@redhat.com)
     - clean up and pad out return codes (indan@nul.nu)
v14: - no change/rebase
v13: - rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
v12: - move to WARN_ON if filter is NULL
       (oleg@redhat.com, luto@mit.edu, keescook@chromium.org)
     - return immediately for filter==NULL (keescook@chromium.org)
     - change evaluation to only compare the ACTION so that layered
       errnos don't result in the lowest one being returned.
       (keeschook@chromium.org)
v11: - check for NULL filter (keescook@chromium.org)
v10: - change loaders to fn
 v9: - n/a
 v8: - update Kconfig to note new need for syscall_set_return_value.
     - reordered such that TRAP behavior follows on later.
     - made the for loop a little less indent-y
 v7: - introduced

Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Will Drewry <wad@chromium.org>
---
 arch/Kconfig            |    6 ++++--
 include/linux/seccomp.h |   15 +++++++++++----
 kernel/seccomp.c        |   47 ++++++++++++++++++++++++++++++++++++++---------
 3 files changed, 53 insertions(+), 15 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 7c6bd48..dd4e067 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -203,8 +203,10 @@ config HAVE_ARCH_SECCOMP_FILTER
 	bool
 	help
 	  This symbol should be selected by an architecure if it provides
-	  asm/syscall.h, specifically syscall_get_arguments() and
-	  syscall_get_arch().
+	  asm/syscall.h, specifically syscall_get_arguments(),
+	  syscall_get_arch(), and syscall_set_return_value().  Additionally,
+	  its system call entry path must respect a return value of -1 from
+	  __secure_computing_int() and/or secure_computing().
 
 config SECCOMP_FILTER
 	def_bool y
diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
index ce980a8..12bb2e3 100644
--- a/include/linux/seccomp.h
+++ b/include/linux/seccomp.h
@@ -12,13 +12,14 @@
 
 /*
  * All BPF programs must return a 32-bit value.
- * The bottom 16-bits are reserved for future use.
+ * The bottom 16-bits are for optional return data.
  * The upper 16-bits are ordered from least permissive values to most.
  *
  * The ordering ensures that a min_t() over composed return values always
  * selects the least permissive choice.
  */
 #define SECCOMP_RET_KILL	0x00000000U /* kill the task immediately */
+#define SECCOMP_RET_ERRNO	0x00050000U /* returns an errno */
 #define SECCOMP_RET_ALLOW	0x7fff0000U /* allow */
 
 /* Masks for the return value sections. */
@@ -64,11 +65,17 @@ struct seccomp {
 	struct seccomp_filter *filter;
 };
 
-extern void __secure_computing(int);
-static inline void secure_computing(int this_syscall)
+/*
+ * Direct callers to __secure_computing should be updated as
+ * CONFIG_HAVE_ARCH_SECCOMP_FILTER propagates.
+ */
+extern void __secure_computing(int) __deprecated;
+extern int __secure_computing_int(int);
+static inline int secure_computing(int this_syscall)
 {
 	if (unlikely(test_thread_flag(TIF_SECCOMP)))
-		__secure_computing(this_syscall);
+		return  __secure_computing_int(this_syscall);
+	return 0;
 }
 
 extern long prctl_get_seccomp(void);
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 51c3462..af3db09 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -195,15 +195,20 @@ static int seccomp_chk_filter(struct sock_filter *filter, unsigned int flen)
 static u32 seccomp_run_filters(int syscall)
 {
 	struct seccomp_filter *f;
-	u32 ret = SECCOMP_RET_KILL;
+	u32 ret = SECCOMP_RET_ALLOW;
+
+	/* Ensure unexpected behavior doesn't result in failing open. */
+	if (WARN_ON(current->seccomp.filter == NULL))
+		return SECCOMP_RET_KILL;
+
 	/*
 	 * All filters are evaluated in order of youngest to oldest. The lowest
-	 * BPF return value always takes priority.
+	 * BPF return value (ignoring the DATA) always takes priority.
 	 */
 	for (f = current->seccomp.filter; f; f = f->prev) {
-		ret = sk_run_filter(NULL, f->insns);
-		if (ret != SECCOMP_RET_ALLOW)
-			break;
+		u32 cur_ret = sk_run_filter(NULL, f->insns);
+		if ((cur_ret & SECCOMP_RET_ACTION) < (ret & SECCOMP_RET_ACTION))
+			ret = cur_ret;
 	}
 	return ret;
 }
@@ -343,9 +348,18 @@ static int mode1_syscalls_32[] = {
 
 void __secure_computing(int this_syscall)
 {
+	/* Filter calls should never use this function. */
+	BUG_ON(current->seccomp.mode == SECCOMP_MODE_FILTER);
+	__secure_computing_int(this_syscall);
+}
+
+int __secure_computing_int(int this_syscall)
+{
 	int mode = current->seccomp.mode;
 	int exit_sig = 0;
 	int *syscall;
+	u32 ret = SECCOMP_RET_KILL;
+	int data;
 
 	switch (mode) {
 	case SECCOMP_MODE_STRICT:
@@ -356,14 +370,26 @@ void __secure_computing(int this_syscall)
 #endif
 		do {
 			if (*syscall == this_syscall)
-				return;
+				return 0;
 		} while (*++syscall);
 		exit_sig = SIGKILL;
 		break;
 #ifdef CONFIG_SECCOMP_FILTER
 	case SECCOMP_MODE_FILTER:
-		if (seccomp_run_filters(this_syscall) == SECCOMP_RET_ALLOW)
-			return;
+		ret = seccomp_run_filters(this_syscall);
+		data = ret & SECCOMP_RET_DATA;
+		switch (code & SECCOMP_RET_ACTION) {
+		case SECCOMP_RET_ERRNO:
+			/* Set the low-order 16-bits as a errno. */
+			syscall_set_return_value(current, task_pt_regs(current),
+						 -data, 0);
+			goto skip;
+		case SECCOMP_RET_ALLOW:
+			return 0;
+		case SECCOMP_RET_KILL:
+		default:
+			break;
+		}
 		exit_sig = SIGSYS;
 		break;
 #endif
@@ -374,8 +400,11 @@ void __secure_computing(int this_syscall)
 #ifdef SECCOMP_DEBUG
 	dump_stack();
 #endif
-	audit_seccomp(this_syscall, exit_code, SECCOMP_RET_KILL);
+	audit_seccomp(this_syscall, exit_sig, ret);
 	do_exit(exit_sig);
+skip:
+	audit_seccomp(this_syscall, exit_sig, ret);
+	return -1;
 }
 
 long prctl_get_seccomp(void)
-- 
1.7.5.4

[kernel-hardening] [PATCH v15 08/13] seccomp: add SECCOMP_RET_ERRNO

[Will Drewry]

This change adds the SECCOMP_RET_ERRNO as a valid return value from a
seccomp filter.  Additionally, it makes the first use of the lower
16-bits for storing a filter-supplied errno.  16-bits is more than
enough for the errno-base.h calls.

Returning errors instead of immediately terminating processes that
violate seccomp policy allow for broader use of this functionality
for kernel attack surface reduction.  For example, a linux container
could maintain a whitelist of pre-existing system calls but drop
all new ones with errnos.  This would keep a logically static attack
surface while providing errnos that may allow for graceful failure
without the downside of do_exit() on a bad call.

v15: - use audit_seccomp and add a skip label. (eparis@redhat.com)
     - clean up and pad out return codes (indan@nul.nu)
v14: - no change/rebase
v13: - rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
v12: - move to WARN_ON if filter is NULL
       (oleg@redhat.com, luto@mit.edu, keescook@chromium.org)
     - return immediately for filter==NULL (keescook@chromium.org)
     - change evaluation to only compare the ACTION so that layered
       errnos don't result in the lowest one being returned.
       (keeschook@chromium.org)
v11: - check for NULL filter (keescook@chromium.org)
v10: - change loaders to fn
 v9: - n/a
 v8: - update Kconfig to note new need for syscall_set_return_value.
     - reordered such that TRAP behavior follows on later.
     - made the for loop a little less indent-y
 v7: - introduced

Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Will Drewry <wad@chromium.org>
---
 arch/Kconfig            |    6 ++++--
 include/linux/seccomp.h |   15 +++++++++++----
 kernel/seccomp.c        |   47 ++++++++++++++++++++++++++++++++++++++---------
 3 files changed, 53 insertions(+), 15 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 7c6bd48..dd4e067 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -203,8 +203,10 @@ config HAVE_ARCH_SECCOMP_FILTER
 	bool
 	help
 	  This symbol should be selected by an architecure if it provides
-	  asm/syscall.h, specifically syscall_get_arguments() and
-	  syscall_get_arch().
+	  asm/syscall.h, specifically syscall_get_arguments(),
+	  syscall_get_arch(), and syscall_set_return_value().  Additionally,
+	  its system call entry path must respect a return value of -1 from
+	  __secure_computing_int() and/or secure_computing().
 
 config SECCOMP_FILTER
 	def_bool y
diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
index ce980a8..12bb2e3 100644
--- a/include/linux/seccomp.h
+++ b/include/linux/seccomp.h
@@ -12,13 +12,14 @@
 
 /*
  * All BPF programs must return a 32-bit value.
- * The bottom 16-bits are reserved for future use.
+ * The bottom 16-bits are for optional return data.
  * The upper 16-bits are ordered from least permissive values to most.
  *
  * The ordering ensures that a min_t() over composed return values always
  * selects the least permissive choice.
  */
 #define SECCOMP_RET_KILL	0x00000000U /* kill the task immediately */
+#define SECCOMP_RET_ERRNO	0x00050000U /* returns an errno */
 #define SECCOMP_RET_ALLOW	0x7fff0000U /* allow */
 
 /* Masks for the return value sections. */
@@ -64,11 +65,17 @@ struct seccomp {
 	struct seccomp_filter *filter;
 };
 
-extern void __secure_computing(int);
-static inline void secure_computing(int this_syscall)
+/*
+ * Direct callers to __secure_computing should be updated as
+ * CONFIG_HAVE_ARCH_SECCOMP_FILTER propagates.
+ */
+extern void __secure_computing(int) __deprecated;
+extern int __secure_computing_int(int);
+static inline int secure_computing(int this_syscall)
 {
 	if (unlikely(test_thread_flag(TIF_SECCOMP)))
-		__secure_computing(this_syscall);
+		return  __secure_computing_int(this_syscall);
+	return 0;
 }
 
 extern long prctl_get_seccomp(void);
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 51c3462..af3db09 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -195,15 +195,20 @@ static int seccomp_chk_filter(struct sock_filter *filter, unsigned int flen)
 static u32 seccomp_run_filters(int syscall)
 {
 	struct seccomp_filter *f;
-	u32 ret = SECCOMP_RET_KILL;
+	u32 ret = SECCOMP_RET_ALLOW;
+
+	/* Ensure unexpected behavior doesn't result in failing open. */
+	if (WARN_ON(current->seccomp.filter == NULL))
+		return SECCOMP_RET_KILL;
+
 	/*
 	 * All filters are evaluated in order of youngest to oldest. The lowest
-	 * BPF return value always takes priority.
+	 * BPF return value (ignoring the DATA) always takes priority.
 	 */
 	for (f = current->seccomp.filter; f; f = f->prev) {
-		ret = sk_run_filter(NULL, f->insns);
-		if (ret != SECCOMP_RET_ALLOW)
-			break;
+		u32 cur_ret = sk_run_filter(NULL, f->insns);
+		if ((cur_ret & SECCOMP_RET_ACTION) < (ret & SECCOMP_RET_ACTION))
+			ret = cur_ret;
 	}
 	return ret;
 }
@@ -343,9 +348,18 @@ static int mode1_syscalls_32[] = {
 
 void __secure_computing(int this_syscall)
 {
+	/* Filter calls should never use this function. */
+	BUG_ON(current->seccomp.mode == SECCOMP_MODE_FILTER);
+	__secure_computing_int(this_syscall);
+}
+
+int __secure_computing_int(int this_syscall)
+{
 	int mode = current->seccomp.mode;
 	int exit_sig = 0;
 	int *syscall;
+	u32 ret = SECCOMP_RET_KILL;
+	int data;
 
 	switch (mode) {
 	case SECCOMP_MODE_STRICT:
@@ -356,14 +370,26 @@ void __secure_computing(int this_syscall)
 #endif
 		do {
 			if (*syscall == this_syscall)
-				return;
+				return 0;
 		} while (*++syscall);
 		exit_sig = SIGKILL;
 		break;
 #ifdef CONFIG_SECCOMP_FILTER
 	case SECCOMP_MODE_FILTER:
-		if (seccomp_run_filters(this_syscall) == SECCOMP_RET_ALLOW)
-			return;
+		ret = seccomp_run_filters(this_syscall);
+		data = ret & SECCOMP_RET_DATA;
+		switch (code & SECCOMP_RET_ACTION) {
+		case SECCOMP_RET_ERRNO:
+			/* Set the low-order 16-bits as a errno. */
+			syscall_set_return_value(current, task_pt_regs(current),
+						 -data, 0);
+			goto skip;
+		case SECCOMP_RET_ALLOW:
+			return 0;
+		case SECCOMP_RET_KILL:
+		default:
+			break;
+		}
 		exit_sig = SIGSYS;
 		break;
 #endif
@@ -374,8 +400,11 @@ void __secure_computing(int this_syscall)
 #ifdef SECCOMP_DEBUG
 	dump_stack();
 #endif
-	audit_seccomp(this_syscall, exit_code, SECCOMP_RET_KILL);
+	audit_seccomp(this_syscall, exit_sig, ret);
 	do_exit(exit_sig);
+skip:
+	audit_seccomp(this_syscall, exit_sig, ret);
+	return -1;
 }
 
 long prctl_get_seccomp(void)
-- 
1.7.5.4

[PATCH v15 09/13] signal, x86: add SIGSYS info and make it synchronous.

[Will Drewry]

This change enables SIGSYS, defines _sigfields._sigsys, and adds
x86 (compat) arch support.  _sigsys defines fields which allow
a signal handler to receive the triggering system call number,
the relevant AUDIT_ARCH_* value for that number, and the address
of the callsite.

SIGSYS is added to the SYNCHRONOUS_MASK because it is desirable for it
to have setup_frame() called for it. The goal is to ensure that
ucontext_t reflects the machine state from the time-of-syscall and not
from another signal handler.

The first consumer of SIGSYS would be seccomp filter.  In particular,
a filter program could specify a new return value, SECCOMP_RET_TRAP,
which would result in the system call being denied and the calling
thread signaled.  This also means that implementing arch-specific
support can be dependent upon HAVE_ARCH_SECCOMP_FILTER.

v14: - rebase/nochanges
v13: - rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
v12: - reworded changelog (oleg@redhat.com)
v11: - fix dropped words in the change description
     - added fallback copy_siginfo support.
     - added __ARCH_SIGSYS define to allow stepped arch support.
v10: - first version based on suggestion

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Suggested-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Will Drewry <wad@chromium.org>
---
 arch/x86/ia32/ia32_signal.c   |    4 ++++
 arch/x86/include/asm/ia32.h   |    6 ++++++
 include/asm-generic/siginfo.h |   22 ++++++++++++++++++++++
 kernel/signal.c               |    9 ++++++++-
 4 files changed, 40 insertions(+), 1 deletions(-)

diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
index 6557769..c81d2c7 100644
--- a/arch/x86/ia32/ia32_signal.c
+++ b/arch/x86/ia32/ia32_signal.c
@@ -73,6 +73,10 @@ int copy_siginfo_to_user32(compat_siginfo_t __user *to, siginfo_t *from)
 			switch (from->si_code >> 16) {
 			case __SI_FAULT >> 16:
 				break;
+			case __SI_SYS >> 16:
+				put_user_ex(from->si_syscall, &to->si_syscall);
+				put_user_ex(from->si_arch, &to->si_arch);
+				break;
 			case __SI_CHLD >> 16:
 				put_user_ex(from->si_utime, &to->si_utime);
 				put_user_ex(from->si_stime, &to->si_stime);
diff --git a/arch/x86/include/asm/ia32.h b/arch/x86/include/asm/ia32.h
index 1f7e625..541485f 100644
--- a/arch/x86/include/asm/ia32.h
+++ b/arch/x86/include/asm/ia32.h
@@ -126,6 +126,12 @@ typedef struct compat_siginfo {
 			int _band;	/* POLL_IN, POLL_OUT, POLL_MSG */
 			int _fd;
 		} _sigpoll;
+
+		struct {
+			unsigned int _call_addr; /* calling insn */
+			int _syscall;	/* triggering system call number */
+			unsigned int _arch;	/* AUDIT_ARCH_* of syscall */
+		} _sigsys;
 	} _sifields;
 } compat_siginfo_t;
 
diff --git a/include/asm-generic/siginfo.h b/include/asm-generic/siginfo.h
index 0dd4e87..31306f5 100644
--- a/include/asm-generic/siginfo.h
+++ b/include/asm-generic/siginfo.h
@@ -90,9 +90,18 @@ typedef struct siginfo {
 			__ARCH_SI_BAND_T _band;	/* POLL_IN, POLL_OUT, POLL_MSG */
 			int _fd;
 		} _sigpoll;
+
+		/* SIGSYS */
+		struct {
+			void __user *_call_addr; /* calling insn */
+			int _syscall;	/* triggering system call number */
+			unsigned int _arch;	/* AUDIT_ARCH_* of syscall */
+		} _sigsys;
 	} _sifields;
 } siginfo_t;
 
+/* If the arch shares siginfo, then it has SIGSYS. */
+#define __ARCH_SIGSYS
 #endif
 
 /*
@@ -116,6 +125,11 @@ typedef struct siginfo {
 #define si_addr_lsb	_sifields._sigfault._addr_lsb
 #define si_band		_sifields._sigpoll._band
 #define si_fd		_sifields._sigpoll._fd
+#ifdef __ARCH_SIGSYS
+#define si_call_addr	_sifields._sigsys._call_addr
+#define si_syscall	_sifields._sigsys._syscall
+#define si_arch		_sifields._sigsys._arch
+#endif
 
 #ifdef __KERNEL__
 #define __SI_MASK	0xffff0000u
@@ -126,6 +140,7 @@ typedef struct siginfo {
 #define __SI_CHLD	(4 << 16)
 #define __SI_RT		(5 << 16)
 #define __SI_MESGQ	(6 << 16)
+#define __SI_SYS	(7 << 16)
 #define __SI_CODE(T,N)	((T) | ((N) & 0xffff))
 #else
 #define __SI_KILL	0
@@ -135,6 +150,7 @@ typedef struct siginfo {
 #define __SI_CHLD	0
 #define __SI_RT		0
 #define __SI_MESGQ	0
+#define __SI_SYS	0
 #define __SI_CODE(T,N)	(N)
 #endif
 
@@ -232,6 +248,12 @@ typedef struct siginfo {
 #define NSIGPOLL	6
 
 /*
+ * SIGSYS si_codes
+ */
+#define SYS_SECCOMP		(__SI_SYS|1)	/* seccomp triggered */
+#define NSIGSYS	1
+
+/*
  * sigevent definitions
  * 
  * It seems likely that SIGEV_THREAD will have to be handled from 
diff --git a/kernel/signal.c b/kernel/signal.c
index c73c428..15a9e9b 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -160,7 +160,7 @@ void recalc_sigpending(void)
 
 #define SYNCHRONOUS_MASK \
 	(sigmask(SIGSEGV) | sigmask(SIGBUS) | sigmask(SIGILL) | \
-	 sigmask(SIGTRAP) | sigmask(SIGFPE))
+	 sigmask(SIGTRAP) | sigmask(SIGFPE) | sigmask(SIGSYS))
 
 int next_signal(struct sigpending *pending, sigset_t *mask)
 {
@@ -2686,6 +2686,13 @@ int copy_siginfo_to_user(siginfo_t __user *to, siginfo_t *from)
 		err |= __put_user(from->si_uid, &to->si_uid);
 		err |= __put_user(from->si_ptr, &to->si_ptr);
 		break;
+#ifdef __ARCH_SIGSYS
+	case __SI_SYS:
+		err |= __put_user(from->si_call_addr, &to->si_call_addr);
+		err |= __put_user(from->si_syscall, &to->si_syscall);
+		err |= __put_user(from->si_arch, &to->si_arch);
+		break;
+#endif
 	default: /* this is just in case for now ... */
 		err |= __put_user(from->si_pid, &to->si_pid);
 		err |= __put_user(from->si_uid, &to->si_uid);
-- 
1.7.5.4

[kernel-hardening] [PATCH v15 09/13] signal, x86: add SIGSYS info and make it synchronous.

[Will Drewry]

This change enables SIGSYS, defines _sigfields._sigsys, and adds
x86 (compat) arch support.  _sigsys defines fields which allow
a signal handler to receive the triggering system call number,
the relevant AUDIT_ARCH_* value for that number, and the address
of the callsite.

SIGSYS is added to the SYNCHRONOUS_MASK because it is desirable for it
to have setup_frame() called for it. The goal is to ensure that
ucontext_t reflects the machine state from the time-of-syscall and not
from another signal handler.

The first consumer of SIGSYS would be seccomp filter.  In particular,
a filter program could specify a new return value, SECCOMP_RET_TRAP,
which would result in the system call being denied and the calling
thread signaled.  This also means that implementing arch-specific
support can be dependent upon HAVE_ARCH_SECCOMP_FILTER.

v14: - rebase/nochanges
v13: - rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
v12: - reworded changelog (oleg@redhat.com)
v11: - fix dropped words in the change description
     - added fallback copy_siginfo support.
     - added __ARCH_SIGSYS define to allow stepped arch support.
v10: - first version based on suggestion

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Suggested-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Will Drewry <wad@chromium.org>
---
 arch/x86/ia32/ia32_signal.c   |    4 ++++
 arch/x86/include/asm/ia32.h   |    6 ++++++
 include/asm-generic/siginfo.h |   22 ++++++++++++++++++++++
 kernel/signal.c               |    9 ++++++++-
 4 files changed, 40 insertions(+), 1 deletions(-)

diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
index 6557769..c81d2c7 100644
--- a/arch/x86/ia32/ia32_signal.c
+++ b/arch/x86/ia32/ia32_signal.c
@@ -73,6 +73,10 @@ int copy_siginfo_to_user32(compat_siginfo_t __user *to, siginfo_t *from)
 			switch (from->si_code >> 16) {
 			case __SI_FAULT >> 16:
 				break;
+			case __SI_SYS >> 16:
+				put_user_ex(from->si_syscall, &to->si_syscall);
+				put_user_ex(from->si_arch, &to->si_arch);
+				break;
 			case __SI_CHLD >> 16:
 				put_user_ex(from->si_utime, &to->si_utime);
 				put_user_ex(from->si_stime, &to->si_stime);
diff --git a/arch/x86/include/asm/ia32.h b/arch/x86/include/asm/ia32.h
index 1f7e625..541485f 100644
--- a/arch/x86/include/asm/ia32.h
+++ b/arch/x86/include/asm/ia32.h
@@ -126,6 +126,12 @@ typedef struct compat_siginfo {
 			int _band;	/* POLL_IN, POLL_OUT, POLL_MSG */
 			int _fd;
 		} _sigpoll;
+
+		struct {
+			unsigned int _call_addr; /* calling insn */
+			int _syscall;	/* triggering system call number */
+			unsigned int _arch;	/* AUDIT_ARCH_* of syscall */
+		} _sigsys;
 	} _sifields;
 } compat_siginfo_t;
 
diff --git a/include/asm-generic/siginfo.h b/include/asm-generic/siginfo.h
index 0dd4e87..31306f5 100644
--- a/include/asm-generic/siginfo.h
+++ b/include/asm-generic/siginfo.h
@@ -90,9 +90,18 @@ typedef struct siginfo {
 			__ARCH_SI_BAND_T _band;	/* POLL_IN, POLL_OUT, POLL_MSG */
 			int _fd;
 		} _sigpoll;
+
+		/* SIGSYS */
+		struct {
+			void __user *_call_addr; /* calling insn */
+			int _syscall;	/* triggering system call number */
+			unsigned int _arch;	/* AUDIT_ARCH_* of syscall */
+		} _sigsys;
 	} _sifields;
 } siginfo_t;
 
+/* If the arch shares siginfo, then it has SIGSYS. */
+#define __ARCH_SIGSYS
 #endif
 
 /*
@@ -116,6 +125,11 @@ typedef struct siginfo {
 #define si_addr_lsb	_sifields._sigfault._addr_lsb
 #define si_band		_sifields._sigpoll._band
 #define si_fd		_sifields._sigpoll._fd
+#ifdef __ARCH_SIGSYS
+#define si_call_addr	_sifields._sigsys._call_addr
+#define si_syscall	_sifields._sigsys._syscall
+#define si_arch		_sifields._sigsys._arch
+#endif
 
 #ifdef __KERNEL__
 #define __SI_MASK	0xffff0000u
@@ -126,6 +140,7 @@ typedef struct siginfo {
 #define __SI_CHLD	(4 << 16)
 #define __SI_RT		(5 << 16)
 #define __SI_MESGQ	(6 << 16)
+#define __SI_SYS	(7 << 16)
 #define __SI_CODE(T,N)	((T) | ((N) & 0xffff))
 #else
 #define __SI_KILL	0
@@ -135,6 +150,7 @@ typedef struct siginfo {
 #define __SI_CHLD	0
 #define __SI_RT		0
 #define __SI_MESGQ	0
+#define __SI_SYS	0
 #define __SI_CODE(T,N)	(N)
 #endif
 
@@ -232,6 +248,12 @@ typedef struct siginfo {
 #define NSIGPOLL	6
 
 /*
+ * SIGSYS si_codes
+ */
+#define SYS_SECCOMP		(__SI_SYS|1)	/* seccomp triggered */
+#define NSIGSYS	1
+
+/*
  * sigevent definitions
  * 
  * It seems likely that SIGEV_THREAD will have to be handled from 
diff --git a/kernel/signal.c b/kernel/signal.c
index c73c428..15a9e9b 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -160,7 +160,7 @@ void recalc_sigpending(void)
 
 #define SYNCHRONOUS_MASK \
 	(sigmask(SIGSEGV) | sigmask(SIGBUS) | sigmask(SIGILL) | \
-	 sigmask(SIGTRAP) | sigmask(SIGFPE))
+	 sigmask(SIGTRAP) | sigmask(SIGFPE) | sigmask(SIGSYS))
 
 int next_signal(struct sigpending *pending, sigset_t *mask)
 {
@@ -2686,6 +2686,13 @@ int copy_siginfo_to_user(siginfo_t __user *to, siginfo_t *from)
 		err |= __put_user(from->si_uid, &to->si_uid);
 		err |= __put_user(from->si_ptr, &to->si_ptr);
 		break;
+#ifdef __ARCH_SIGSYS
+	case __SI_SYS:
+		err |= __put_user(from->si_call_addr, &to->si_call_addr);
+		err |= __put_user(from->si_syscall, &to->si_syscall);
+		err |= __put_user(from->si_arch, &to->si_arch);
+		break;
+#endif
 	default: /* this is just in case for now ... */
 		err |= __put_user(from->si_pid, &to->si_pid);
 		err |= __put_user(from->si_uid, &to->si_uid);
-- 
1.7.5.4

[PATCH v15 10/13] seccomp: Add SECCOMP_RET_TRAP

[Will Drewry]

Adds a new return value to seccomp filters that triggers a SIGSYS to be
delivered with the new SYS_SECCOMP si_code.

This allows in-process system call emulation, including just specifying
an errno or cleanly dumping core, rather than just dying.

v15: - use audit_seccomp/skip
     - pad out error spacing; clean up switch (indan@nul.nu)
v14: - n/a
v13: - rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
v12: - rebase on to linux-next
v11: - clarify the comment (indan@nul.nu)
     - s/sigtrap/sigsys
v10: - use SIGSYS, syscall_get_arch, updates arch/Kconfig
       note suggested-by (though original suggestion had other behaviors)
v9:  - changes to SIGILL
v8:  - clean up based on changes to dependent patches
v7:  - introduction

Suggested-by: Markus Gutschke <markus@chromium.org>
Suggested-by: Julien Tinnes <jln@chromium.org>
Signed-off-by: Will Drewry <wad@chromium.org>
---
 arch/Kconfig                  |   14 +++++++++-----
 include/asm-generic/siginfo.h |    2 +-
 include/linux/seccomp.h       |    1 +
 kernel/seccomp.c              |   26 ++++++++++++++++++++++++++
 4 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index dd4e067..d92a78e 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -202,11 +202,15 @@ config HAVE_CMPXCHG_DOUBLE
 config HAVE_ARCH_SECCOMP_FILTER
 	bool
 	help
-	  This symbol should be selected by an architecure if it provides
-	  asm/syscall.h, specifically syscall_get_arguments(),
-	  syscall_get_arch(), and syscall_set_return_value().  Additionally,
-	  its system call entry path must respect a return value of -1 from
-	  __secure_computing_int() and/or secure_computing().
+	  This symbol should be selected by an architecure if it provides:
+	  asm/syscall.h:
+	  - syscall_get_arch()
+	  - syscall_get_arguments()
+	  - syscall_rollback()
+	  - syscall_set_return_value()
+	  SIGSYS siginfo_t support must be implemented.
+	  __secure_computing_int()/secure_computing()'s return value must be
+	  checked, with -1 resulting in the syscall being skipped.
 
 config SECCOMP_FILTER
 	def_bool y
diff --git a/include/asm-generic/siginfo.h b/include/asm-generic/siginfo.h
index 31306f5..af5d035 100644
--- a/include/asm-generic/siginfo.h
+++ b/include/asm-generic/siginfo.h
@@ -93,7 +93,7 @@ typedef struct siginfo {
 
 		/* SIGSYS */
 		struct {
-			void __user *_call_addr; /* calling insn */
+			void __user *_call_addr; /* calling user insn */
 			int _syscall;	/* triggering system call number */
 			unsigned int _arch;	/* AUDIT_ARCH_* of syscall */
 		} _sigsys;
diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
index 12bb2e3..a5078fb 100644
--- a/include/linux/seccomp.h
+++ b/include/linux/seccomp.h
@@ -19,6 +19,7 @@
  * selects the least permissive choice.
  */
 #define SECCOMP_RET_KILL	0x00000000U /* kill the task immediately */
+#define SECCOMP_RET_TRAP	0x00030000U /* disallow and force a SIGSYS */
 #define SECCOMP_RET_ERRNO	0x00050000U /* returns an errno */
 #define SECCOMP_RET_ALLOW	0x7fff0000U /* allow */
 
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index af3db09..fb3b993 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -327,6 +327,26 @@ void put_seccomp_filter(struct task_struct *tsk)
 		kfree(freeme);
 	}
 }
+
+/**
+ * seccomp_send_sigsys - signals the task to allow in-process syscall emulation
+ * @syscall: syscall number to send to userland
+ * @reason: filter-supplied reason code to send to userland (via si_errno)
+ *
+ * Forces a SIGSYS with a code of SYS_SECCOMP and related sigsys info.
+ */
+static void seccomp_send_sigsys(int syscall, int reason)
+{
+	struct siginfo info;
+	memset(&info, 0, sizeof(info));
+	info.si_signo = SIGSYS;
+	info.si_code = SYS_SECCOMP;
+	info.si_call_addr = (void __user *)KSTK_EIP(current);
+	info.si_errno = reason;
+	info.si_arch = syscall_get_arch(current, task_pt_regs(current));
+	info.si_syscall = syscall;
+	force_sig_info(SIGSYS, &info, current);
+}
 #endif	/* CONFIG_SECCOMP_FILTER */
 
 /*
@@ -384,6 +404,12 @@ int __secure_computing_int(int this_syscall)
 			syscall_set_return_value(current, task_pt_regs(current),
 						 -data, 0);
 			goto skip;
+		case SECCOMP_RET_TRAP:
+			/* Show the handler the original registers. */
+			syscall_rollback(current, task_pt_regs(current));
+			/* Let the filter pass back 16 bits of data. */
+			seccomp_send_sigsys(this_syscall, data);
+			goto skip;
 		case SECCOMP_RET_ALLOW:
 			return 0;
 		case SECCOMP_RET_KILL:
-- 
1.7.5.4

[kernel-hardening] [PATCH v15 10/13] seccomp: Add SECCOMP_RET_TRAP

[Will Drewry]

Adds a new return value to seccomp filters that triggers a SIGSYS to be
delivered with the new SYS_SECCOMP si_code.

This allows in-process system call emulation, including just specifying
an errno or cleanly dumping core, rather than just dying.

v15: - use audit_seccomp/skip
     - pad out error spacing; clean up switch (indan@nul.nu)
v14: - n/a
v13: - rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
v12: - rebase on to linux-next
v11: - clarify the comment (indan@nul.nu)
     - s/sigtrap/sigsys
v10: - use SIGSYS, syscall_get_arch, updates arch/Kconfig
       note suggested-by (though original suggestion had other behaviors)
v9:  - changes to SIGILL
v8:  - clean up based on changes to dependent patches
v7:  - introduction

Suggested-by: Markus Gutschke <markus@chromium.org>
Suggested-by: Julien Tinnes <jln@chromium.org>
Signed-off-by: Will Drewry <wad@chromium.org>
---
 arch/Kconfig                  |   14 +++++++++-----
 include/asm-generic/siginfo.h |    2 +-
 include/linux/seccomp.h       |    1 +
 kernel/seccomp.c              |   26 ++++++++++++++++++++++++++
 4 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index dd4e067..d92a78e 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -202,11 +202,15 @@ config HAVE_CMPXCHG_DOUBLE
 config HAVE_ARCH_SECCOMP_FILTER
 	bool
 	help
-	  This symbol should be selected by an architecure if it provides
-	  asm/syscall.h, specifically syscall_get_arguments(),
-	  syscall_get_arch(), and syscall_set_return_value().  Additionally,
-	  its system call entry path must respect a return value of -1 from
-	  __secure_computing_int() and/or secure_computing().
+	  This symbol should be selected by an architecure if it provides:
+	  asm/syscall.h:
+	  - syscall_get_arch()
+	  - syscall_get_arguments()
+	  - syscall_rollback()
+	  - syscall_set_return_value()
+	  SIGSYS siginfo_t support must be implemented.
+	  __secure_computing_int()/secure_computing()'s return value must be
+	  checked, with -1 resulting in the syscall being skipped.
 
 config SECCOMP_FILTER
 	def_bool y
diff --git a/include/asm-generic/siginfo.h b/include/asm-generic/siginfo.h
index 31306f5..af5d035 100644
--- a/include/asm-generic/siginfo.h
+++ b/include/asm-generic/siginfo.h
@@ -93,7 +93,7 @@ typedef struct siginfo {
 
 		/* SIGSYS */
 		struct {
-			void __user *_call_addr; /* calling insn */
+			void __user *_call_addr; /* calling user insn */
 			int _syscall;	/* triggering system call number */
 			unsigned int _arch;	/* AUDIT_ARCH_* of syscall */
 		} _sigsys;
diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
index 12bb2e3..a5078fb 100644
--- a/include/linux/seccomp.h
+++ b/include/linux/seccomp.h
@@ -19,6 +19,7 @@
  * selects the least permissive choice.
  */
 #define SECCOMP_RET_KILL	0x00000000U /* kill the task immediately */
+#define SECCOMP_RET_TRAP	0x00030000U /* disallow and force a SIGSYS */
 #define SECCOMP_RET_ERRNO	0x00050000U /* returns an errno */
 #define SECCOMP_RET_ALLOW	0x7fff0000U /* allow */
 
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index af3db09..fb3b993 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -327,6 +327,26 @@ void put_seccomp_filter(struct task_struct *tsk)
 		kfree(freeme);
 	}
 }
+
+/**
+ * seccomp_send_sigsys - signals the task to allow in-process syscall emulation
+ * @syscall: syscall number to send to userland
+ * @reason: filter-supplied reason code to send to userland (via si_errno)
+ *
+ * Forces a SIGSYS with a code of SYS_SECCOMP and related sigsys info.
+ */
+static void seccomp_send_sigsys(int syscall, int reason)
+{
+	struct siginfo info;
+	memset(&info, 0, sizeof(info));
+	info.si_signo = SIGSYS;
+	info.si_code = SYS_SECCOMP;
+	info.si_call_addr = (void __user *)KSTK_EIP(current);
+	info.si_errno = reason;
+	info.si_arch = syscall_get_arch(current, task_pt_regs(current));
+	info.si_syscall = syscall;
+	force_sig_info(SIGSYS, &info, current);
+}
 #endif	/* CONFIG_SECCOMP_FILTER */
 
 /*
@@ -384,6 +404,12 @@ int __secure_computing_int(int this_syscall)
 			syscall_set_return_value(current, task_pt_regs(current),
 						 -data, 0);
 			goto skip;
+		case SECCOMP_RET_TRAP:
+			/* Show the handler the original registers. */
+			syscall_rollback(current, task_pt_regs(current));
+			/* Let the filter pass back 16 bits of data. */
+			seccomp_send_sigsys(this_syscall, data);
+			goto skip;
 		case SECCOMP_RET_ALLOW:
 			return 0;
 		case SECCOMP_RET_KILL:
-- 
1.7.5.4

[PATCH v15 11/13] ptrace,seccomp: Add PTRACE_SECCOMP support

[Will Drewry]

This change adds support for a new ptrace option, PTRACE_O_TRACESECCOMP,
and a new return value for seccomp BPF programs, SECCOMP_RET_TRACE.

When a tracer specifies the PTRACE_O_TRACESECCOMP ptrace option, the
tracer will be notified, via PTRACE_EVENT_SECCOMP, for any syscall that
results in a BPF program returning SECCOMP_RET_TRACE.  The 16-bit
SECCOMP_RET_DATA mask of the BPF program return value will be passed as
the ptrace_message and may be retrieved using PTRACE_GETEVENTMSG.

If the subordinate process is not using seccomp filter, then no
system call notifications will occur even if the option is specified.

If there is no tracer with PTRACE_O_TRACESECCOMP when SECCOMP_RET_TRACE
is returned, the system call will not be executed and an -ENOSYS errno
will be returned to userspace.

This change adds a dependency on the system call slow path.  Any future
efforts to use the system call fast path for seccomp filter will need to
address this restriction.

v15: - add audit support for non-zero return codes
     - clean up style (indan@nul.nu)
v14: - rebase/nochanges
v13: - rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
       (Brings back a change to ptrace.c and the masks.)
v12: - rebase to linux-next
     - use ptrace_event and update arch/Kconfig to mention slow-path dependency
     - drop all tracehook changes and inclusion (oleg@redhat.com)
v11: - invert the logic to just make it a PTRACE_SYSCALL accelerator
       (indan@nul.nu)
v10: - moved to PTRACE_O_SECCOMP / PT_TRACE_SECCOMP
v9:  - n/a
v8:  - guarded PTRACE_SECCOMP use with an ifdef
v7:  - introduced

Signed-off-by: Will Drewry <wad@chromium.org>
---
 arch/Kconfig            |   11 ++++++-----
 include/linux/ptrace.h  |    7 +++++--
 include/linux/seccomp.h |    1 +
 kernel/ptrace.c         |    3 +++
 kernel/seccomp.c        |   13 +++++++++++--
 5 files changed, 26 insertions(+), 9 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index d92a78e..3f8132c 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -202,15 +202,16 @@ config HAVE_CMPXCHG_DOUBLE
 config HAVE_ARCH_SECCOMP_FILTER
 	bool
 	help
-	  This symbol should be selected by an architecure if it provides:
-	  asm/syscall.h:
+	  An arch should select this symbol if it provides all of these things:
 	  - syscall_get_arch()
 	  - syscall_get_arguments()
 	  - syscall_rollback()
 	  - syscall_set_return_value()
-	  SIGSYS siginfo_t support must be implemented.
-	  __secure_computing_int()/secure_computing()'s return value must be
-	  checked, with -1 resulting in the syscall being skipped.
+	  - SIGSYS siginfo_t support
+	  - uses __secure_computing_int() or secure_computing()
+	  - secure_computing is called from a ptrace_event()-safe context
+	  - secure_computing return value is checked and a return value of -1
+	    results in the system call being skipped immediately.
 
 config SECCOMP_FILTER
 	def_bool y
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index c2f1f6a..84b3418 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -62,8 +62,9 @@
 #define PTRACE_O_TRACEEXEC	0x00000010
 #define PTRACE_O_TRACEVFORKDONE	0x00000020
 #define PTRACE_O_TRACEEXIT	0x00000040
+#define PTRACE_O_TRACESECCOMP	0x00000080
 
-#define PTRACE_O_MASK		0x0000007f
+#define PTRACE_O_MASK		0x000000ff
 
 /* Wait extended result codes for the above trace options.  */
 #define PTRACE_EVENT_FORK	1
@@ -73,6 +74,7 @@
 #define PTRACE_EVENT_VFORK_DONE	5
 #define PTRACE_EVENT_EXIT	6
 #define PTRACE_EVENT_STOP	7
+#define PTRACE_EVENT_SECCOMP	8
 
 #include <asm/ptrace.h>
 
@@ -101,8 +103,9 @@
 #define PT_TRACE_EXEC		PT_EVENT_FLAG(PTRACE_EVENT_EXEC)
 #define PT_TRACE_VFORK_DONE	PT_EVENT_FLAG(PTRACE_EVENT_VFORK_DONE)
 #define PT_TRACE_EXIT		PT_EVENT_FLAG(PTRACE_EVENT_EXIT)
+#define PT_TRACE_SECCOMP	PT_EVENT_FLAG(PTRACE_EVENT_SECCOMP)
 
-#define PT_TRACE_MASK	0x000003f4
+#define PT_TRACE_MASK	0x00000ff4
 
 /* single stepping state bits (used on ARM and PA-RISC) */
 #define PT_SINGLESTEP_BIT	31
diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
index a5078fb..306733e 100644
--- a/include/linux/seccomp.h
+++ b/include/linux/seccomp.h
@@ -21,6 +21,7 @@
 #define SECCOMP_RET_KILL	0x00000000U /* kill the task immediately */
 #define SECCOMP_RET_TRAP	0x00030000U /* disallow and force a SIGSYS */
 #define SECCOMP_RET_ERRNO	0x00050000U /* returns an errno */
+#define SECCOMP_RET_TRACE	0x7ff00000U /* pass to a tracer or disallow */
 #define SECCOMP_RET_ALLOW	0x7fff0000U /* allow */
 
 /* Masks for the return value sections. */
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 00ab2ca..8cf6da1 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -551,6 +551,9 @@ static int ptrace_setoptions(struct task_struct *child, unsigned long data)
 	if (data & PTRACE_O_TRACEEXIT)
 		child->ptrace |= PT_TRACE_EXIT;
 
+	if (data & PTRACE_O_TRACESECCOMP)
+		child->ptrace |= PT_TRACE_SECCOMP;
+
 	return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
 }
 
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index fb3b993..725e83e 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -17,13 +17,13 @@
 #include <linux/audit.h>
 #include <linux/compat.h>
 #include <linux/filter.h>
+#include <linux/ptrace.h>
 #include <linux/sched.h>
 #include <linux/seccomp.h>
 #include <linux/security.h>
 #include <linux/slab.h>
 #include <linux/uaccess.h>
 
-#include <linux/tracehook.h>
 #include <asm/syscall.h>
 
 /* #define SECCOMP_DEBUG 1 */
@@ -398,7 +398,7 @@ int __secure_computing_int(int this_syscall)
 	case SECCOMP_MODE_FILTER:
 		ret = seccomp_run_filters(this_syscall);
 		data = ret & SECCOMP_RET_DATA;
-		switch (code & SECCOMP_RET_ACTION) {
+		switch (ret & SECCOMP_RET_ACTION) {
 		case SECCOMP_RET_ERRNO:
 			/* Set the low-order 16-bits as a errno. */
 			syscall_set_return_value(current, task_pt_regs(current),
@@ -410,6 +410,15 @@ int __secure_computing_int(int this_syscall)
 			/* Let the filter pass back 16 bits of data. */
 			seccomp_send_sigsys(this_syscall, data);
 			goto skip;
+		case SECCOMP_RET_TRACE:
+			/* Skip these calls if there is no tracer. */
+			if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP))
+				goto skip;
+			/* Allow the BPF to provide the event message */
+			ptrace_event(PTRACE_EVENT_SECCOMP, data);
+			if (fatal_signal_pending(current))
+				break;
+			return 0;
 		case SECCOMP_RET_ALLOW:
 			return 0;
 		case SECCOMP_RET_KILL:
-- 
1.7.5.4

[kernel-hardening] [PATCH v15 11/13] ptrace,seccomp: Add PTRACE_SECCOMP support

[Will Drewry]

This change adds support for a new ptrace option, PTRACE_O_TRACESECCOMP,
and a new return value for seccomp BPF programs, SECCOMP_RET_TRACE.

When a tracer specifies the PTRACE_O_TRACESECCOMP ptrace option, the
tracer will be notified, via PTRACE_EVENT_SECCOMP, for any syscall that
results in a BPF program returning SECCOMP_RET_TRACE.  The 16-bit
SECCOMP_RET_DATA mask of the BPF program return value will be passed as
the ptrace_message and may be retrieved using PTRACE_GETEVENTMSG.

If the subordinate process is not using seccomp filter, then no
system call notifications will occur even if the option is specified.

If there is no tracer with PTRACE_O_TRACESECCOMP when SECCOMP_RET_TRACE
is returned, the system call will not be executed and an -ENOSYS errno
will be returned to userspace.

This change adds a dependency on the system call slow path.  Any future
efforts to use the system call fast path for seccomp filter will need to
address this restriction.

v15: - add audit support for non-zero return codes
     - clean up style (indan@nul.nu)
v14: - rebase/nochanges
v13: - rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
       (Brings back a change to ptrace.c and the masks.)
v12: - rebase to linux-next
     - use ptrace_event and update arch/Kconfig to mention slow-path dependency
     - drop all tracehook changes and inclusion (oleg@redhat.com)
v11: - invert the logic to just make it a PTRACE_SYSCALL accelerator
       (indan@nul.nu)
v10: - moved to PTRACE_O_SECCOMP / PT_TRACE_SECCOMP
v9:  - n/a
v8:  - guarded PTRACE_SECCOMP use with an ifdef
v7:  - introduced

Signed-off-by: Will Drewry <wad@chromium.org>
---
 arch/Kconfig            |   11 ++++++-----
 include/linux/ptrace.h  |    7 +++++--
 include/linux/seccomp.h |    1 +
 kernel/ptrace.c         |    3 +++
 kernel/seccomp.c        |   13 +++++++++++--
 5 files changed, 26 insertions(+), 9 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index d92a78e..3f8132c 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -202,15 +202,16 @@ config HAVE_CMPXCHG_DOUBLE
 config HAVE_ARCH_SECCOMP_FILTER
 	bool
 	help
-	  This symbol should be selected by an architecure if it provides:
-	  asm/syscall.h:
+	  An arch should select this symbol if it provides all of these things:
 	  - syscall_get_arch()
 	  - syscall_get_arguments()
 	  - syscall_rollback()
 	  - syscall_set_return_value()
-	  SIGSYS siginfo_t support must be implemented.
-	  __secure_computing_int()/secure_computing()'s return value must be
-	  checked, with -1 resulting in the syscall being skipped.
+	  - SIGSYS siginfo_t support
+	  - uses __secure_computing_int() or secure_computing()
+	  - secure_computing is called from a ptrace_event()-safe context
+	  - secure_computing return value is checked and a return value of -1
+	    results in the system call being skipped immediately.
 
 config SECCOMP_FILTER
 	def_bool y
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index c2f1f6a..84b3418 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -62,8 +62,9 @@
 #define PTRACE_O_TRACEEXEC	0x00000010
 #define PTRACE_O_TRACEVFORKDONE	0x00000020
 #define PTRACE_O_TRACEEXIT	0x00000040
+#define PTRACE_O_TRACESECCOMP	0x00000080
 
-#define PTRACE_O_MASK		0x0000007f
+#define PTRACE_O_MASK		0x000000ff
 
 /* Wait extended result codes for the above trace options.  */
 #define PTRACE_EVENT_FORK	1
@@ -73,6 +74,7 @@
 #define PTRACE_EVENT_VFORK_DONE	5
 #define PTRACE_EVENT_EXIT	6
 #define PTRACE_EVENT_STOP	7
+#define PTRACE_EVENT_SECCOMP	8
 
 #include <asm/ptrace.h>
 
@@ -101,8 +103,9 @@
 #define PT_TRACE_EXEC		PT_EVENT_FLAG(PTRACE_EVENT_EXEC)
 #define PT_TRACE_VFORK_DONE	PT_EVENT_FLAG(PTRACE_EVENT_VFORK_DONE)
 #define PT_TRACE_EXIT		PT_EVENT_FLAG(PTRACE_EVENT_EXIT)
+#define PT_TRACE_SECCOMP	PT_EVENT_FLAG(PTRACE_EVENT_SECCOMP)
 
-#define PT_TRACE_MASK	0x000003f4
+#define PT_TRACE_MASK	0x00000ff4
 
 /* single stepping state bits (used on ARM and PA-RISC) */
 #define PT_SINGLESTEP_BIT	31
diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
index a5078fb..306733e 100644
--- a/include/linux/seccomp.h
+++ b/include/linux/seccomp.h
@@ -21,6 +21,7 @@
 #define SECCOMP_RET_KILL	0x00000000U /* kill the task immediately */
 #define SECCOMP_RET_TRAP	0x00030000U /* disallow and force a SIGSYS */
 #define SECCOMP_RET_ERRNO	0x00050000U /* returns an errno */
+#define SECCOMP_RET_TRACE	0x7ff00000U /* pass to a tracer or disallow */
 #define SECCOMP_RET_ALLOW	0x7fff0000U /* allow */
 
 /* Masks for the return value sections. */
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 00ab2ca..8cf6da1 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -551,6 +551,9 @@ static int ptrace_setoptions(struct task_struct *child, unsigned long data)
 	if (data & PTRACE_O_TRACEEXIT)
 		child->ptrace |= PT_TRACE_EXIT;
 
+	if (data & PTRACE_O_TRACESECCOMP)
+		child->ptrace |= PT_TRACE_SECCOMP;
+
 	return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
 }
 
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index fb3b993..725e83e 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -17,13 +17,13 @@
 #include <linux/audit.h>
 #include <linux/compat.h>
 #include <linux/filter.h>
+#include <linux/ptrace.h>
 #include <linux/sched.h>
 #include <linux/seccomp.h>
 #include <linux/security.h>
 #include <linux/slab.h>
 #include <linux/uaccess.h>
 
-#include <linux/tracehook.h>
 #include <asm/syscall.h>
 
 /* #define SECCOMP_DEBUG 1 */
@@ -398,7 +398,7 @@ int __secure_computing_int(int this_syscall)
 	case SECCOMP_MODE_FILTER:
 		ret = seccomp_run_filters(this_syscall);
 		data = ret & SECCOMP_RET_DATA;
-		switch (code & SECCOMP_RET_ACTION) {
+		switch (ret & SECCOMP_RET_ACTION) {
 		case SECCOMP_RET_ERRNO:
 			/* Set the low-order 16-bits as a errno. */
 			syscall_set_return_value(current, task_pt_regs(current),
@@ -410,6 +410,15 @@ int __secure_computing_int(int this_syscall)
 			/* Let the filter pass back 16 bits of data. */
 			seccomp_send_sigsys(this_syscall, data);
 			goto skip;
+		case SECCOMP_RET_TRACE:
+			/* Skip these calls if there is no tracer. */
+			if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP))
+				goto skip;
+			/* Allow the BPF to provide the event message */
+			ptrace_event(PTRACE_EVENT_SECCOMP, data);
+			if (fatal_signal_pending(current))
+				break;
+			return 0;
 		case SECCOMP_RET_ALLOW:
 			return 0;
 		case SECCOMP_RET_KILL:
-- 
1.7.5.4

[PATCH v15 12/13] x86: Enable HAVE_ARCH_SECCOMP_FILTER

[Will Drewry]

Enable support for seccomp filter on x86:
- asm/tracehook.h exists
- syscall_get_arguments() works
- syscall_rollback() works
- ptrace_report_syscall() works
- secure_computing() return value is honored (see below)

This also adds support for honoring the return
value from secure_computing().

SECCOMP_RET_TRACE and SECCOMP_RET_TRAP may result in seccomp needing to
skip a system call without killing the process.  This is done by
returning a non-zero (-1) value from secure_computing.  This change
makes x86 respect that return value.

To ensure that minimal kernel code is exposed, a non-zero return value
results in an immediate return to user space (with an invalid syscall
number).

Signed-off-by: Will Drewry <wad@chromium.org>
---
 arch/x86/Kconfig         |    1 +
 arch/x86/kernel/ptrace.c |    7 ++++++-
 2 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 5bed94e..4c9012b 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -82,6 +82,7 @@ config X86
 	select CLKEVT_I8253
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select GENERIC_IOMAP
+	select HAVE_ARCH_SECCOMP_FILTER
 
 config INSTRUCTION_DECODER
 	def_bool (KPROBES || PERF_EVENTS)
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 5026738..90d465a 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -1380,7 +1380,11 @@ long syscall_trace_enter(struct pt_regs *regs)
 		regs->flags |= X86_EFLAGS_TF;
 
 	/* do the secure computing check first */
-	secure_computing(regs->orig_ax);
+	if (secure_computing(regs->orig_ax)) {
+		/* seccomp failures shouldn't expose any additional code. */
+		ret = -1L;
+		goto out;
+	}
 
 	if (unlikely(test_thread_flag(TIF_SYSCALL_EMU)))
 		ret = -1L;
@@ -1405,6 +1409,7 @@ long syscall_trace_enter(struct pt_regs *regs)
 				    regs->dx, regs->r10);
 #endif
 
+out:
 	return ret ?: regs->orig_ax;
 }
 
-- 
1.7.5.4

[kernel-hardening] [PATCH v15 12/13] x86: Enable HAVE_ARCH_SECCOMP_FILTER

[Will Drewry]

Enable support for seccomp filter on x86:
- asm/tracehook.h exists
- syscall_get_arguments() works
- syscall_rollback() works
- ptrace_report_syscall() works
- secure_computing() return value is honored (see below)

This also adds support for honoring the return
value from secure_computing().

SECCOMP_RET_TRACE and SECCOMP_RET_TRAP may result in seccomp needing to
skip a system call without killing the process.  This is done by
returning a non-zero (-1) value from secure_computing.  This change
makes x86 respect that return value.

To ensure that minimal kernel code is exposed, a non-zero return value
results in an immediate return to user space (with an invalid syscall
number).

Signed-off-by: Will Drewry <wad@chromium.org>
---
 arch/x86/Kconfig         |    1 +
 arch/x86/kernel/ptrace.c |    7 ++++++-
 2 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 5bed94e..4c9012b 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -82,6 +82,7 @@ config X86
 	select CLKEVT_I8253
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select GENERIC_IOMAP
+	select HAVE_ARCH_SECCOMP_FILTER
 
 config INSTRUCTION_DECODER
 	def_bool (KPROBES || PERF_EVENTS)
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 5026738..90d465a 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -1380,7 +1380,11 @@ long syscall_trace_enter(struct pt_regs *regs)
 		regs->flags |= X86_EFLAGS_TF;
 
 	/* do the secure computing check first */
-	secure_computing(regs->orig_ax);
+	if (secure_computing(regs->orig_ax)) {
+		/* seccomp failures shouldn't expose any additional code. */
+		ret = -1L;
+		goto out;
+	}
 
 	if (unlikely(test_thread_flag(TIF_SYSCALL_EMU)))
 		ret = -1L;
@@ -1405,6 +1409,7 @@ long syscall_trace_enter(struct pt_regs *regs)
 				    regs->dx, regs->r10);
 #endif
 
+out:
 	return ret ?: regs->orig_ax;
 }
 
-- 
1.7.5.4

[PATCH v15 13/13] Documentation: prctl/seccomp_filter

[Will Drewry]

Documents how system call filtering using Berkeley Packet
Filter programs works and how it may be used.
Includes an example for x86 and a semi-generic
example using a macro-based code generator.

v14: - rebase/nochanges
v13: - rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
v12: - comment on the ptrace_event use
     - update arch support comment
     - note the behavior of SECCOMP_RET_DATA when there are multiple filters
       (keescook@chromium.org)
     - lots of samples/ clean up incl 64-bit bpf-direct support
       (markus@chromium.org)
     - rebase to linux-next
v11: - overhaul return value language, updates (keescook@chromium.org)
     - comment on do_exit(SIGSYS)
v10: - update for SIGSYS
     - update for new seccomp_data layout
     - update for ptrace option use
v9: - updated bpf-direct.c for SIGILL
v8: - add PR_SET_NO_NEW_PRIVS to the samples.
v7: - updated for all the new stuff in v7: TRAP, TRACE
    - only talk about PR_SET_SECCOMP now
    - fixed bad JLE32 check (coreyb@linux.vnet.ibm.com)
    - adds dropper.c: a simple system call disabler
v6: - tweak the language to note the requirement of
      PR_SET_NO_NEW_PRIVS being called prior to use. (luto@mit.edu)
v5: - update sample to use system call arguments
    - adds a "fancy" example using a macro-based generator
    - cleaned up bpf in the sample
    - update docs to mention arguments
    - fix prctl value (eparis@redhat.com)
    - language cleanup (rdunlap@xenotime.net)
v4: - update for no_new_privs use
    - minor tweaks
v3: - call out BPF <-> Berkeley Packet Filter (rdunlap@xenotime.net)
    - document use of tentative always-unprivileged
    - guard sample compilation for i386 and x86_64
v2: - move code to samples (corbet@lwn.net)

Signed-off-by: Will Drewry <wad@chromium.org>
---
 Documentation/prctl/seccomp_filter.txt |  156 +++++++++++++++++++++
 samples/Makefile                       |    2 +-
 samples/seccomp/Makefile               |   38 +++++
 samples/seccomp/bpf-direct.c           |  176 +++++++++++++++++++++++
 samples/seccomp/bpf-fancy.c            |  102 ++++++++++++++
 samples/seccomp/bpf-helper.c           |   89 ++++++++++++
 samples/seccomp/bpf-helper.h           |  238 ++++++++++++++++++++++++++++++++
 samples/seccomp/dropper.c              |   68 +++++++++
 8 files changed, 868 insertions(+), 1 deletions(-)
 create mode 100644 Documentation/prctl/seccomp_filter.txt
 create mode 100644 samples/seccomp/Makefile
 create mode 100644 samples/seccomp/bpf-direct.c
 create mode 100644 samples/seccomp/bpf-fancy.c
 create mode 100644 samples/seccomp/bpf-helper.c
 create mode 100644 samples/seccomp/bpf-helper.h
 create mode 100644 samples/seccomp/dropper.c

diff --git a/Documentation/prctl/seccomp_filter.txt b/Documentation/prctl/seccomp_filter.txt
new file mode 100644
index 0000000..4aa3e78
--- /dev/null
+++ b/Documentation/prctl/seccomp_filter.txt
@@ -0,0 +1,156 @@
+		SECure COMPuting with filters
+		=============================
+
+Introduction
+------------
+
+A large number of system calls are exposed to every userland process
+with many of them going unused for the entire lifetime of the process.
+As system calls change and mature, bugs are found and eradicated.  A
+certain subset of userland applications benefit by having a reduced set
+of available system calls.  The resulting set reduces the total kernel
+surface exposed to the application.  System call filtering is meant for
+use with those applications.
+
+Seccomp filtering provides a means for a process to specify a filter for
+incoming system calls.  The filter is expressed as a Berkeley Packet
+Filter (BPF) program, as with socket filters, except that the data
+operated on is related to the system call being made: system call
+number and the system call arguments.  This allows for expressive
+filtering of system calls using a filter program language with a long
+history of being exposed to userland and a straightforward data set.
+
+Additionally, BPF makes it impossible for users of seccomp to fall prey
+to time-of-check-time-of-use (TOCTOU) attacks that are common in system
+call interposition frameworks.  BPF programs may not dereference
+pointers which constrains all filters to solely evaluating the system
+call arguments directly.
+
+What it isn't
+-------------
+
+System call filtering isn't a sandbox.  It provides a clearly defined
+mechanism for minimizing the exposed kernel surface.  It is meant to be
+a tool for sandbox developers to use.  Beyond that, policy for logical
+behavior and information flow should be managed with a combination of
+other system hardening techniques and, potentially, an LSM of your
+choosing.  Expressive, dynamic filters provide further options down this
+path (avoiding pathological sizes or selecting which of the multiplexed
+system calls in socketcall() is allowed, for instance) which could be
+construed, incorrectly, as a more complete sandboxing solution.
+
+Usage
+-----
+
+An additional seccomp mode is added and is enabled using the same
+prctl(2) call as the strict seccomp.  If the architecture has
+CONFIG_HAVE_ARCH_SECCOMP_FILTER, then filters may be added as below:
+
+PR_SET_SECCOMP:
+	Now takes an additional argument which specifies a new filter
+	using a BPF program.
+	The BPF program will be executed over struct seccomp_data
+	reflecting the system call number, arguments, and other
+	metadata.  The BPF program must then return one of the
+	acceptable values to inform the kernel which action should be
+	taken.
+
+	Usage:
+		prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, prog);
+
+	The 'prog' argument is a pointer to a struct sock_fprog which
+	will contain the filter program.  If the program is invalid, the
+	call will return -1 and set errno to EINVAL.
+
+	Note, is_compat_task is also tracked for the @prog.  This means
+	that once set the calling task will have all of its system calls
+	blocked if it switches its system call ABI.
+
+	If fork/clone and execve are allowed by @prog, any child
+	processes will be constrained to the same filters and system
+	call ABI as the parent.
+
+	Prior to use, the task must call prctl(PR_SET_NO_NEW_PRIVS, 1) or
+	run with CAP_SYS_ADMIN privileges in its namespace.  If these are not
+	true, -EACCES will be returned.  This requirement ensures that filter
+	programs cannot be applied to child processes with greater privileges
+	than the task that installed them.
+
+	Additionally, if prctl(2) is allowed by the attached filter,
+	additional filters may be layered on which will increase evaluation
+	time, but allow for further decreasing the attack surface during
+	execution of a process.
+
+The above call returns 0 on success and non-zero on error.
+
+Return values
+-------------
+A seccomp filter may return any of the following values. If multiple
+filters exist, the return value for the evaluation of a given system
+call will always use the highest precedent value. (For example,
+SECCOMP_RET_KILL will always take precedence.)
+
+In precedence order, they are:
+
+SECCOMP_RET_KILL:
+	Results in the task exiting immediately without executing the
+	system call.  The exit status of the task (status & 0x7f) will
+	be SIGSYS, not SIGKILL.
+
+SECCOMP_RET_TRAP:
+	Results in the kernel sending a SIGSYS signal to the triggering
+	task without executing the system call.  The kernel will
+	rollback the register state to just before the system call
+	entry such that a signal handler in the task will be able to
+	inspect the ucontext_t->uc_mcontext registers and emulate
+	system call success or failure upon return from the signal
+	handler.
+
+	The SECCOMP_RET_DATA portion of the return value will be passed
+	as si_errno.
+
+	SIGSYS triggered by seccomp will have a si_code of SYS_SECCOMP.
+
+SECCOMP_RET_ERRNO:
+	Results in the lower 16-bits of the return value being passed
+	to userland as the errno without executing the system call.
+
+SECCOMP_RET_TRACE:
+	When returned, this value will cause the kernel to attempt to
+	notify a ptrace()-based tracer prior to executing the system
+	call.  If there is no tracer present, -ENOSYS is returned to
+	userland and the system call is not executed.
+
+	A tracer will be notified if it requests PTRACE_O_TRACESECCOMP
+	using ptrace(PTRACE_SETOPTIONS).  The tracer will be notified
+	of a PTRACE_EVENT_SECCOMP and the SECCOMP_RET_DATA portion of
+	the BPF program return value will be available to the tracer
+	via PTRACE_GETEVENTMSG.
+
+SECCOMP_RET_ALLOW:
+	Results in the system call being executed.
+
+If multiple filters exist, the return value for the evaluation of a
+given system call will always use the highest precedent value.
+
+Precedence is only determined using the SECCOMP_RET_ACTION mask.  When
+multiple filters return values of the same precedence, only the
+SECCOMP_RET_DATA from the most recently installed filter will be
+returned.
+
+
+Example
+-------
+
+The samples/seccomp/ directory contains both an x86-specific example
+and a more generic example of a higher level macro interface for BPF
+program generation.
+
+Adding architecture support
+-----------------------
+
+See arch/Kconfig for the authoritative requirements.  In general, if an
+architecture supports both ptrace_event and seccomp, it will be able to
+support seccomp filter with minor fixup: SIGSYS support and seccomp return
+value checking.  Then it must just add CONFIG_HAVE_ARCH_SECCOMP_FILTER
+to its arch-specific Kconfig.
diff --git a/samples/Makefile b/samples/Makefile
index 6280817..f29b19c 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -1,4 +1,4 @@
 # Makefile for Linux samples code
 
 obj-$(CONFIG_SAMPLES)	+= kobject/ kprobes/ tracepoints/ trace_events/ \
-			   hw_breakpoint/ kfifo/ kdb/ hidraw/
+			   hw_breakpoint/ kfifo/ kdb/ hidraw/ seccomp/
diff --git a/samples/seccomp/Makefile b/samples/seccomp/Makefile
new file mode 100644
index 0000000..e8fe0f5
--- /dev/null
+++ b/samples/seccomp/Makefile
@@ -0,0 +1,38 @@
+# kbuild trick to avoid linker error. Can be omitted if a module is built.
+obj- := dummy.o
+
+hostprogs-$(CONFIG_SECCOMP) := bpf-fancy dropper
+bpf-fancy-objs := bpf-fancy.o bpf-helper.o
+
+HOSTCFLAGS_bpf-fancy.o += -I$(objtree)/usr/include
+HOSTCFLAGS_bpf-fancy.o += -idirafter $(objtree)/include
+HOSTCFLAGS_bpf-helper.o += -I$(objtree)/usr/include
+HOSTCFLAGS_bpf-helper.o += -idirafter $(objtree)/include
+
+HOSTCFLAGS_dropper.o += -I$(objtree)/usr/include
+HOSTCFLAGS_dropper.o += -idirafter $(objtree)/include
+dropper-objs := dropper.o
+
+# bpf-direct.c is x86-only.
+ifeq ($(SRCARCH),x86)
+# List of programs to build
+hostprogs-$(CONFIG_SECCOMP) += bpf-direct
+bpf-direct-objs := bpf-direct.o
+endif
+
+HOSTCFLAGS_bpf-direct.o += -I$(objtree)/usr/include
+HOSTCFLAGS_bpf-direct.o += -idirafter $(objtree)/include
+
+# Try to match the kernel target.
+ifeq ($(CONFIG_64BIT),)
+HOSTCFLAGS_bpf-direct.o += -m32
+HOSTCFLAGS_dropper.o += -m32
+HOSTCFLAGS_bpf-helper.o += -m32
+HOSTCFLAGS_bpf-fancy.o += -m32
+HOSTLOADLIBES_bpf-direct += -m32
+HOSTLOADLIBES_bpf-fancy += -m32
+HOSTLOADLIBES_dropper += -m32
+endif
+
+# Tell kbuild to always build the programs
+always := $(hostprogs-y)
diff --git a/samples/seccomp/bpf-direct.c b/samples/seccomp/bpf-direct.c
new file mode 100644
index 0000000..f1567ad
--- /dev/null
+++ b/samples/seccomp/bpf-direct.c
@@ -0,0 +1,176 @@
+/*
+ * Seccomp filter example for x86 (32-bit and 64-bit) with BPF macros
+ *
+ * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>
+ * Author: Will Drewry <wad@chromium.org>
+ *
+ * The code may be used by anyone for any purpose,
+ * and can serve as a starting point for developing
+ * applications using prctl(PR_SET_SECCOMP, 2, ...).
+ */
+#define __USE_GNU 1
+#define _GNU_SOURCE 1
+
+#include <linux/types.h>
+#include <linux/filter.h>
+#include <linux/seccomp.h>
+#include <linux/unistd.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stddef.h>
+#include <string.h>
+#include <sys/prctl.h>
+#include <unistd.h>
+
+#define syscall_arg(_n) (offsetof(struct seccomp_data, args[_n]))
+#define syscall_nr (offsetof(struct seccomp_data, nr))
+
+#if defined(__i386__)
+#define REG_RESULT	REG_EAX
+#define REG_SYSCALL	REG_EAX
+#define REG_ARG0	REG_EBX
+#define REG_ARG1	REG_ECX
+#define REG_ARG2	REG_EDX
+#define REG_ARG3	REG_ESI
+#define REG_ARG4	REG_EDI
+#define REG_ARG5	REG_EBP
+#elif defined(__x86_64__)
+#define REG_RESULT	REG_RAX
+#define REG_SYSCALL	REG_RAX
+#define REG_ARG0	REG_RDI
+#define REG_ARG1	REG_RSI
+#define REG_ARG2	REG_RDX
+#define REG_ARG3	REG_R10
+#define REG_ARG4	REG_R8
+#define REG_ARG5	REG_R9
+#else
+#error Unsupported platform
+#endif
+
+#ifndef PR_SET_NO_NEW_PRIVS
+#define PR_SET_NO_NEW_PRIVS 36
+#endif
+
+#ifndef SYS_SECCOMP
+#define SYS_SECCOMP 1
+#endif
+
+static void emulator(int nr, siginfo_t *info, void *void_context)
+{
+	ucontext_t *ctx = (ucontext_t *)(void_context);
+	int syscall;
+	char *buf;
+	ssize_t bytes;
+	size_t len;
+	if (info->si_code != SYS_SECCOMP)
+		return;
+	if (!ctx)
+		return;
+	syscall = ctx->uc_mcontext.gregs[REG_SYSCALL];
+	buf = (char *) ctx->uc_mcontext.gregs[REG_ARG1];
+	len = (size_t) ctx->uc_mcontext.gregs[REG_ARG2];
+
+	if (syscall != __NR_write)
+		return;
+	if (ctx->uc_mcontext.gregs[REG_ARG0] != STDERR_FILENO)
+		return;
+	/* Redirect stderr messages to stdout. Doesn't handle EINTR, etc */
+	ctx->uc_mcontext.gregs[REG_RESULT] = -1;
+	if (write(STDOUT_FILENO, "[ERR] ", 6) > 0) {
+		bytes = write(STDOUT_FILENO, buf, len);
+		ctx->uc_mcontext.gregs[REG_RESULT] = bytes;
+	}
+	return;
+}
+
+static int install_emulator(void)
+{
+	struct sigaction act;
+	sigset_t mask;
+	memset(&act, 0, sizeof(act));
+	sigemptyset(&mask);
+	sigaddset(&mask, SIGSYS);
+
+	act.sa_sigaction = &emulator;
+	act.sa_flags = SA_SIGINFO;
+	if (sigaction(SIGSYS, &act, NULL) < 0) {
+		perror("sigaction");
+		return -1;
+	}
+	if (sigprocmask(SIG_UNBLOCK, &mask, NULL)) {
+		perror("sigprocmask");
+		return -1;
+	}
+	return 0;
+}
+
+static int install_filter(void)
+{
+	struct sock_filter filter[] = {
+		/* Grab the system call number */
+		BPF_STMT(BPF_LD+BPF_W+BPF_ABS, syscall_nr),
+		/* Jump table for the allowed syscalls */
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_rt_sigreturn, 0, 1),
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
+#ifdef __NR_sigreturn
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_sigreturn, 0, 1),
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
+#endif
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_exit_group, 0, 1),
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_exit, 0, 1),
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_read, 1, 0),
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_write, 3, 2),
+
+		/* Check that read is only using stdin. */
+		BPF_STMT(BPF_LD+BPF_W+BPF_ABS, syscall_arg(0)),
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, STDIN_FILENO, 4, 0),
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL),
+
+		/* Check that write is only using stdout */
+		BPF_STMT(BPF_LD+BPF_W+BPF_ABS, syscall_arg(0)),
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, STDOUT_FILENO, 1, 0),
+		/* Trap attempts to write to stderr */
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, STDERR_FILENO, 1, 2),
+
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_TRAP),
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL),
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)(sizeof(filter)/sizeof(filter[0])),
+		.filter = filter,
+	};
+
+	if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
+		perror("prctl(NO_NEW_PRIVS)");
+		return 1;
+	}
+
+
+	if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog)) {
+		perror("prctl");
+		return 1;
+	}
+	return 0;
+}
+
+#define payload(_c) (_c), sizeof((_c))
+int main(int argc, char **argv)
+{
+	char buf[4096];
+	ssize_t bytes = 0;
+	if (install_emulator())
+		return 1;
+	if (install_filter())
+		return 1;
+	syscall(__NR_write, STDOUT_FILENO,
+		payload("OHAI! WHAT IS YOUR NAME? "));
+	bytes = syscall(__NR_read, STDIN_FILENO, buf, sizeof(buf));
+	syscall(__NR_write, STDOUT_FILENO, payload("HELLO, "));
+	syscall(__NR_write, STDOUT_FILENO, buf, bytes);
+	syscall(__NR_write, STDERR_FILENO,
+		payload("Error message going to STDERR\n"));
+	return 0;
+}
diff --git a/samples/seccomp/bpf-fancy.c b/samples/seccomp/bpf-fancy.c
new file mode 100644
index 0000000..bf1f6b5
--- /dev/null
+++ b/samples/seccomp/bpf-fancy.c
@@ -0,0 +1,102 @@
+/*
+ * Seccomp BPF example using a macro-based generator.
+ *
+ * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>
+ * Author: Will Drewry <wad@chromium.org>
+ *
+ * The code may be used by anyone for any purpose,
+ * and can serve as a starting point for developing
+ * applications using prctl(PR_ATTACH_SECCOMP_FILTER).
+ */
+
+#include <linux/filter.h>
+#include <linux/seccomp.h>
+#include <linux/unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/prctl.h>
+#include <unistd.h>
+
+#include "bpf-helper.h"
+
+#ifndef PR_SET_NO_NEW_PRIVS
+#define PR_SET_NO_NEW_PRIVS 36
+#endif
+
+int main(int argc, char **argv)
+{
+	struct bpf_labels l;
+	static const char msg1[] = "Please type something: ";
+	static const char msg2[] = "You typed: ";
+	char buf[256];
+	struct sock_filter filter[] = {
+		/* TODO: LOAD_SYSCALL_NR(arch) and enforce an arch */
+		LOAD_SYSCALL_NR,
+		SYSCALL(__NR_exit, ALLOW),
+		SYSCALL(__NR_exit_group, ALLOW),
+		SYSCALL(__NR_write, JUMP(&l, write_fd)),
+		SYSCALL(__NR_read, JUMP(&l, read)),
+		DENY,  /* Don't passthrough into a label */
+
+		LABEL(&l, read),
+		ARG(0),
+		JNE(STDIN_FILENO, DENY),
+		ARG(1),
+		JNE((unsigned long)buf, DENY),
+		ARG(2),
+		JGE(sizeof(buf), DENY),
+		ALLOW,
+
+		LABEL(&l, write_fd),
+		ARG(0),
+		JEQ(STDOUT_FILENO, JUMP(&l, write_buf)),
+		JEQ(STDERR_FILENO, JUMP(&l, write_buf)),
+		DENY,
+
+		LABEL(&l, write_buf),
+		ARG(1),
+		JEQ((unsigned long)msg1, JUMP(&l, msg1_len)),
+		JEQ((unsigned long)msg2, JUMP(&l, msg2_len)),
+		JEQ((unsigned long)buf, JUMP(&l, buf_len)),
+		DENY,
+
+		LABEL(&l, msg1_len),
+		ARG(2),
+		JLT(sizeof(msg1), ALLOW),
+		DENY,
+
+		LABEL(&l, msg2_len),
+		ARG(2),
+		JLT(sizeof(msg2), ALLOW),
+		DENY,
+
+		LABEL(&l, buf_len),
+		ARG(2),
+		JLT(sizeof(buf), ALLOW),
+		DENY,
+	};
+	struct sock_fprog prog = {
+		.filter = filter,
+		.len = (unsigned short)(sizeof(filter)/sizeof(filter[0])),
+	};
+	ssize_t bytes;
+	bpf_resolve_jumps(&l, filter, sizeof(filter)/sizeof(*filter));
+
+	if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
+		perror("prctl(NO_NEW_PRIVS)");
+		return 1;
+	}
+
+	if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog)) {
+		perror("prctl(SECCOMP)");
+		return 1;
+	}
+	syscall(__NR_write, STDOUT_FILENO, msg1, strlen(msg1));
+	bytes = syscall(__NR_read, STDIN_FILENO, buf, sizeof(buf)-1);
+	bytes = (bytes > 0 ? bytes : 0);
+	syscall(__NR_write, STDERR_FILENO, msg2, strlen(msg2));
+	syscall(__NR_write, STDERR_FILENO, buf, bytes);
+	/* Now get killed */
+	syscall(__NR_write, STDERR_FILENO, msg2, strlen(msg2)+2);
+	return 0;
+}
diff --git a/samples/seccomp/bpf-helper.c b/samples/seccomp/bpf-helper.c
new file mode 100644
index 0000000..579cfe3
--- /dev/null
+++ b/samples/seccomp/bpf-helper.c
@@ -0,0 +1,89 @@
+/*
+ * Seccomp BPF helper functions
+ *
+ * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>
+ * Author: Will Drewry <wad@chromium.org>
+ *
+ * The code may be used by anyone for any purpose,
+ * and can serve as a starting point for developing
+ * applications using prctl(PR_ATTACH_SECCOMP_FILTER).
+ */
+
+#include <stdio.h>
+#include <string.h>
+
+#include "bpf-helper.h"
+
+int bpf_resolve_jumps(struct bpf_labels *labels,
+		      struct sock_filter *filter, size_t count)
+{
+	struct sock_filter *begin = filter;
+	__u8 insn = count - 1;
+
+	if (count < 1)
+		return -1;
+	/*
+	* Walk it once, backwards, to build the label table and do fixups.
+	* Since backward jumps are disallowed by BPF, this is easy.
+	*/
+	filter += insn;
+	for (; filter >= begin; --insn, --filter) {
+		if (filter->code != (BPF_JMP+BPF_JA))
+			continue;
+		switch ((filter->jt<<8)|filter->jf) {
+		case (JUMP_JT<<8)|JUMP_JF:
+			if (labels->labels[filter->k].location == 0xffffffff) {
+				fprintf(stderr, "Unresolved label: '%s'\n",
+					labels->labels[filter->k].label);
+				return 1;
+			}
+			filter->k = labels->labels[filter->k].location -
+				    (insn + 1);
+			filter->jt = 0;
+			filter->jf = 0;
+			continue;
+		case (LABEL_JT<<8)|LABEL_JF:
+			if (labels->labels[filter->k].location != 0xffffffff) {
+				fprintf(stderr, "Duplicate label use: '%s'\n",
+					labels->labels[filter->k].label);
+				return 1;
+			}
+			labels->labels[filter->k].location = insn;
+			filter->k = 0; /* fall through */
+			filter->jt = 0;
+			filter->jf = 0;
+			continue;
+		}
+	}
+	return 0;
+}
+
+/* Simple lookup table for labels. */
+__u32 seccomp_bpf_label(struct bpf_labels *labels, const char *label)
+{
+	struct __bpf_label *begin = labels->labels, *end;
+	int id;
+	if (labels->count == 0) {
+		begin->label = label;
+		begin->location = 0xffffffff;
+		labels->count++;
+		return 0;
+	}
+	end = begin + labels->count;
+	for (id = 0; begin < end; ++begin, ++id) {
+		if (!strcmp(label, begin->label))
+			return id;
+	}
+	begin->label = label;
+	begin->location = 0xffffffff;
+	labels->count++;
+	return id;
+}
+
+void seccomp_bpf_print(struct sock_filter *filter, size_t count)
+{
+	struct sock_filter *end = filter + count;
+	for ( ; filter < end; ++filter)
+		printf("{ code=%u,jt=%u,jf=%u,k=%u },\n",
+			filter->code, filter->jt, filter->jf, filter->k);
+}
diff --git a/samples/seccomp/bpf-helper.h b/samples/seccomp/bpf-helper.h
new file mode 100644
index 0000000..643279d
--- /dev/null
+++ b/samples/seccomp/bpf-helper.h
@@ -0,0 +1,238 @@
+/*
+ * Example wrapper around BPF macros.
+ *
+ * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>
+ * Author: Will Drewry <wad@chromium.org>
+ *
+ * The code may be used by anyone for any purpose,
+ * and can serve as a starting point for developing
+ * applications using prctl(PR_SET_SECCOMP, 2, ...).
+ *
+ * No guarantees are provided with respect to the correctness
+ * or functionality of this code.
+ */
+#ifndef __BPF_HELPER_H__
+#define __BPF_HELPER_H__
+
+#include <asm/bitsperlong.h>	/* for __BITS_PER_LONG */
+#include <endian.h>
+#include <linux/filter.h>
+#include <linux/seccomp.h>	/* for seccomp_data */
+#include <linux/types.h>
+#include <linux/unistd.h>
+#include <stddef.h>
+
+#define BPF_LABELS_MAX 256
+struct bpf_labels {
+	int count;
+	struct __bpf_label {
+		const char *label;
+		__u32 location;
+	} labels[BPF_LABELS_MAX];
+};
+
+int bpf_resolve_jumps(struct bpf_labels *labels,
+		      struct sock_filter *filter, size_t count);
+__u32 seccomp_bpf_label(struct bpf_labels *labels, const char *label);
+void seccomp_bpf_print(struct sock_filter *filter, size_t count);
+
+#define JUMP_JT 0xff
+#define JUMP_JF 0xff
+#define LABEL_JT 0xfe
+#define LABEL_JF 0xfe
+
+#define ALLOW \
+	BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW)
+#define DENY \
+	BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL)
+#define JUMP(labels, label) \
+	BPF_JUMP(BPF_JMP+BPF_JA, FIND_LABEL((labels), (label)), \
+		 JUMP_JT, JUMP_JF)
+#define LABEL(labels, label) \
+	BPF_JUMP(BPF_JMP+BPF_JA, FIND_LABEL((labels), (label)), \
+		 LABEL_JT, LABEL_JF)
+#define SYSCALL(nr, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (nr), 0, 1), \
+	jt
+
+/* Lame, but just an example */
+#define FIND_LABEL(labels, label) seccomp_bpf_label((labels), #label)
+
+#define EXPAND(...) __VA_ARGS__
+/* Map all width-sensitive operations */
+#if __BITS_PER_LONG == 32
+
+#define JEQ(x, jt) JEQ32(x, EXPAND(jt))
+#define JNE(x, jt) JNE32(x, EXPAND(jt))
+#define JGT(x, jt) JGT32(x, EXPAND(jt))
+#define JLT(x, jt) JLT32(x, EXPAND(jt))
+#define JGE(x, jt) JGE32(x, EXPAND(jt))
+#define JLE(x, jt) JLE32(x, EXPAND(jt))
+#define JA(x, jt) JA32(x, EXPAND(jt))
+#define ARG(i) ARG_32(i)
+#define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)])
+
+#elif __BITS_PER_LONG == 64
+
+/* Ensure that we load the logically correct offset. */
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+#define ENDIAN(_lo, _hi) _lo, _hi
+#define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)])
+#define HI_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) + sizeof(__u32)
+#elif __BYTE_ORDER == __BIG_ENDIAN
+#define ENDIAN(_lo, _hi) _hi, _lo
+#define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) + sizeof(__u32)
+#define HI_ARG(idx) offsetof(struct seccomp_data, args[(idx)])
+#else
+#error "Unknown endianness"
+#endif
+
+union arg64 {
+	struct {
+		__u32 ENDIAN(lo32, hi32);
+	};
+	__u64 u64;
+};
+
+#define JEQ(x, jt) \
+	JEQ64(((union arg64){.u64 = (x)}).lo32, \
+	      ((union arg64){.u64 = (x)}).hi32, \
+	      EXPAND(jt))
+#define JGT(x, jt) \
+	JGT64(((union arg64){.u64 = (x)}).lo32, \
+	      ((union arg64){.u64 = (x)}).hi32, \
+	      EXPAND(jt))
+#define JGE(x, jt) \
+	JGE64(((union arg64){.u64 = (x)}).lo32, \
+	      ((union arg64){.u64 = (x)}).hi32, \
+	      EXPAND(jt))
+#define JNE(x, jt) \
+	JNE64(((union arg64){.u64 = (x)}).lo32, \
+	      ((union arg64){.u64 = (x)}).hi32, \
+	      EXPAND(jt))
+#define JLT(x, jt) \
+	JLT64(((union arg64){.u64 = (x)}).lo32, \
+	      ((union arg64){.u64 = (x)}).hi32, \
+	      EXPAND(jt))
+#define JLE(x, jt) \
+	JLE64(((union arg64){.u64 = (x)}).lo32, \
+	      ((union arg64){.u64 = (x)}).hi32, \
+	      EXPAND(jt))
+
+#define JA(x, jt) \
+	JA64(((union arg64){.u64 = (x)}).lo32, \
+	       ((union arg64){.u64 = (x)}).hi32, \
+	       EXPAND(jt))
+#define ARG(i) ARG_64(i)
+
+#else
+#error __BITS_PER_LONG value unusable.
+#endif
+
+/* Loads the arg into A */
+#define ARG_32(idx) \
+	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, LO_ARG(idx))
+
+/* Loads hi into A and lo in X */
+#define ARG_64(idx) \
+	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, LO_ARG(idx)), \
+	BPF_STMT(BPF_ST, 0), /* lo -> M[0] */ \
+	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, HI_ARG(idx)), \
+	BPF_STMT(BPF_ST, 1) /* hi -> M[1] */
+
+#define JEQ32(value, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (value), 0, 1), \
+	jt
+
+#define JNE32(value, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (value), 1, 0), \
+	jt
+
+/* Checks the lo, then swaps to check the hi. A=lo,X=hi */
+#define JEQ64(lo, hi, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
+	BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 0, 2), \
+	BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+	jt, \
+	BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+
+#define JNE64(lo, hi, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 5, 0), \
+	BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 2, 0), \
+	BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+	jt, \
+	BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+
+#define JA32(value, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (value), 0, 1), \
+	jt
+
+#define JA64(lo, hi, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (hi), 3, 0), \
+	BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+	BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (lo), 0, 2), \
+	BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+	jt, \
+	BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+
+#define JGE32(value, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 0, 1), \
+	jt
+
+#define JLT32(value, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 1, 0), \
+	jt
+
+/* Shortcut checking if hi > arg.hi. */
+#define JGE64(lo, hi, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
+	BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+	BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (lo), 0, 2), \
+	BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+	jt, \
+	BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+
+#define JLT64(lo, hi, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (hi), 0, 4), \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
+	BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+	BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 2, 0), \
+	BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+	jt, \
+	BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+
+#define JGT32(value, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 0, 1), \
+	jt
+
+#define JLE32(value, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 1, 0), \
+	jt
+
+/* Check hi > args.hi first, then do the GE checking */
+#define JGT64(lo, hi, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
+	BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+	BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 0, 2), \
+	BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+	jt, \
+	BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+
+#define JLE64(lo, hi, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 6, 0), \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 3), \
+	BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+	BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 2, 0), \
+	BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+	jt, \
+	BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+
+#define LOAD_SYSCALL_NR \
+	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
+		 offsetof(struct seccomp_data, nr))
+
+#endif  /* __BPF_HELPER_H__ */
diff --git a/samples/seccomp/dropper.c b/samples/seccomp/dropper.c
new file mode 100644
index 0000000..c69c347
--- /dev/null
+++ b/samples/seccomp/dropper.c
@@ -0,0 +1,68 @@
+/*
+ * Naive system call dropper built on seccomp_filter.
+ *
+ * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>
+ * Author: Will Drewry <wad@chromium.org>
+ *
+ * The code may be used by anyone for any purpose,
+ * and can serve as a starting point for developing
+ * applications using prctl(PR_SET_SECCOMP, 2, ...).
+ *
+ * When run, returns the specified errno for the specified
+ * system call number against the given architecture.
+ *
+ * Run this one as root as PR_SET_NO_NEW_PRIVS is not called.
+ */
+
+#include <errno.h>
+#include <linux/audit.h>
+#include <linux/filter.h>
+#include <linux/seccomp.h>
+#include <linux/unistd.h>
+#include <stdio.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <sys/prctl.h>
+#include <unistd.h>
+
+static int install_filter(int nr, int arch, int error)
+{
+	struct sock_filter filter[] = {
+		BPF_STMT(BPF_LD+BPF_W+BPF_ABS,
+			 (offsetof(struct seccomp_data, arch))),
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, arch, 0, 3),
+		BPF_STMT(BPF_LD+BPF_W+BPF_ABS,
+			 (offsetof(struct seccomp_data, nr))),
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, nr, 0, 1),
+		BPF_STMT(BPF_RET+BPF_K,
+			 SECCOMP_RET_ERRNO|(error & SECCOMP_RET_DATA)),
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)(sizeof(filter)/sizeof(filter[0])),
+		.filter = filter,
+	};
+	if (prctl(PR_SET_SECCOMP, 2, &prog)) {
+		perror("prctl");
+		return 1;
+	}
+	return 0;
+}
+
+int main(int argc, char **argv)
+{
+	if (argc < 5) {
+		fprintf(stderr, "Usage:\n"
+			"dropper <syscall_nr> <arch> <errno> <prog> [<args>]\n"
+			"Hint:	AUDIT_ARCH_I386: 0x%X\n"
+			"	AUDIT_ARCH_X86_64: 0x%X\n"
+			"\n", AUDIT_ARCH_I386, AUDIT_ARCH_X86_64);
+		return 1;
+	}
+	if (install_filter(strtol(argv[1], NULL, 0), strtol(argv[2], NULL, 0),
+			   strtol(argv[3], NULL, 0)))
+		return 1;
+	execv(argv[4], &argv[4]);
+	printf("Failed to execv\n");
+	return 255;
+}
-- 
1.7.5.4

[kernel-hardening] [PATCH v15 13/13] Documentation: prctl/seccomp_filter

[Will Drewry]

Documents how system call filtering using Berkeley Packet
Filter programs works and how it may be used.
Includes an example for x86 and a semi-generic
example using a macro-based code generator.

v14: - rebase/nochanges
v13: - rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
v12: - comment on the ptrace_event use
     - update arch support comment
     - note the behavior of SECCOMP_RET_DATA when there are multiple filters
       (keescook@chromium.org)
     - lots of samples/ clean up incl 64-bit bpf-direct support
       (markus@chromium.org)
     - rebase to linux-next
v11: - overhaul return value language, updates (keescook@chromium.org)
     - comment on do_exit(SIGSYS)
v10: - update for SIGSYS
     - update for new seccomp_data layout
     - update for ptrace option use
v9: - updated bpf-direct.c for SIGILL
v8: - add PR_SET_NO_NEW_PRIVS to the samples.
v7: - updated for all the new stuff in v7: TRAP, TRACE
    - only talk about PR_SET_SECCOMP now
    - fixed bad JLE32 check (coreyb@linux.vnet.ibm.com)
    - adds dropper.c: a simple system call disabler
v6: - tweak the language to note the requirement of
      PR_SET_NO_NEW_PRIVS being called prior to use. (luto@mit.edu)
v5: - update sample to use system call arguments
    - adds a "fancy" example using a macro-based generator
    - cleaned up bpf in the sample
    - update docs to mention arguments
    - fix prctl value (eparis@redhat.com)
    - language cleanup (rdunlap@xenotime.net)
v4: - update for no_new_privs use
    - minor tweaks
v3: - call out BPF <-> Berkeley Packet Filter (rdunlap@xenotime.net)
    - document use of tentative always-unprivileged
    - guard sample compilation for i386 and x86_64
v2: - move code to samples (corbet@lwn.net)

Signed-off-by: Will Drewry <wad@chromium.org>
---
 Documentation/prctl/seccomp_filter.txt |  156 +++++++++++++++++++++
 samples/Makefile                       |    2 +-
 samples/seccomp/Makefile               |   38 +++++
 samples/seccomp/bpf-direct.c           |  176 +++++++++++++++++++++++
 samples/seccomp/bpf-fancy.c            |  102 ++++++++++++++
 samples/seccomp/bpf-helper.c           |   89 ++++++++++++
 samples/seccomp/bpf-helper.h           |  238 ++++++++++++++++++++++++++++++++
 samples/seccomp/dropper.c              |   68 +++++++++
 8 files changed, 868 insertions(+), 1 deletions(-)
 create mode 100644 Documentation/prctl/seccomp_filter.txt
 create mode 100644 samples/seccomp/Makefile
 create mode 100644 samples/seccomp/bpf-direct.c
 create mode 100644 samples/seccomp/bpf-fancy.c
 create mode 100644 samples/seccomp/bpf-helper.c
 create mode 100644 samples/seccomp/bpf-helper.h
 create mode 100644 samples/seccomp/dropper.c

diff --git a/Documentation/prctl/seccomp_filter.txt b/Documentation/prctl/seccomp_filter.txt
new file mode 100644
index 0000000..4aa3e78
--- /dev/null
+++ b/Documentation/prctl/seccomp_filter.txt
@@ -0,0 +1,156 @@
+		SECure COMPuting with filters
+		=============================
+
+Introduction
+------------
+
+A large number of system calls are exposed to every userland process
+with many of them going unused for the entire lifetime of the process.
+As system calls change and mature, bugs are found and eradicated.  A
+certain subset of userland applications benefit by having a reduced set
+of available system calls.  The resulting set reduces the total kernel
+surface exposed to the application.  System call filtering is meant for
+use with those applications.
+
+Seccomp filtering provides a means for a process to specify a filter for
+incoming system calls.  The filter is expressed as a Berkeley Packet
+Filter (BPF) program, as with socket filters, except that the data
+operated on is related to the system call being made: system call
+number and the system call arguments.  This allows for expressive
+filtering of system calls using a filter program language with a long
+history of being exposed to userland and a straightforward data set.
+
+Additionally, BPF makes it impossible for users of seccomp to fall prey
+to time-of-check-time-of-use (TOCTOU) attacks that are common in system
+call interposition frameworks.  BPF programs may not dereference
+pointers which constrains all filters to solely evaluating the system
+call arguments directly.
+
+What it isn't
+-------------
+
+System call filtering isn't a sandbox.  It provides a clearly defined
+mechanism for minimizing the exposed kernel surface.  It is meant to be
+a tool for sandbox developers to use.  Beyond that, policy for logical
+behavior and information flow should be managed with a combination of
+other system hardening techniques and, potentially, an LSM of your
+choosing.  Expressive, dynamic filters provide further options down this
+path (avoiding pathological sizes or selecting which of the multiplexed
+system calls in socketcall() is allowed, for instance) which could be
+construed, incorrectly, as a more complete sandboxing solution.
+
+Usage
+-----
+
+An additional seccomp mode is added and is enabled using the same
+prctl(2) call as the strict seccomp.  If the architecture has
+CONFIG_HAVE_ARCH_SECCOMP_FILTER, then filters may be added as below:
+
+PR_SET_SECCOMP:
+	Now takes an additional argument which specifies a new filter
+	using a BPF program.
+	The BPF program will be executed over struct seccomp_data
+	reflecting the system call number, arguments, and other
+	metadata.  The BPF program must then return one of the
+	acceptable values to inform the kernel which action should be
+	taken.
+
+	Usage:
+		prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, prog);
+
+	The 'prog' argument is a pointer to a struct sock_fprog which
+	will contain the filter program.  If the program is invalid, the
+	call will return -1 and set errno to EINVAL.
+
+	Note, is_compat_task is also tracked for the @prog.  This means
+	that once set the calling task will have all of its system calls
+	blocked if it switches its system call ABI.
+
+	If fork/clone and execve are allowed by @prog, any child
+	processes will be constrained to the same filters and system
+	call ABI as the parent.
+
+	Prior to use, the task must call prctl(PR_SET_NO_NEW_PRIVS, 1) or
+	run with CAP_SYS_ADMIN privileges in its namespace.  If these are not
+	true, -EACCES will be returned.  This requirement ensures that filter
+	programs cannot be applied to child processes with greater privileges
+	than the task that installed them.
+
+	Additionally, if prctl(2) is allowed by the attached filter,
+	additional filters may be layered on which will increase evaluation
+	time, but allow for further decreasing the attack surface during
+	execution of a process.
+
+The above call returns 0 on success and non-zero on error.
+
+Return values
+-------------
+A seccomp filter may return any of the following values. If multiple
+filters exist, the return value for the evaluation of a given system
+call will always use the highest precedent value. (For example,
+SECCOMP_RET_KILL will always take precedence.)
+
+In precedence order, they are:
+
+SECCOMP_RET_KILL:
+	Results in the task exiting immediately without executing the
+	system call.  The exit status of the task (status & 0x7f) will
+	be SIGSYS, not SIGKILL.
+
+SECCOMP_RET_TRAP:
+	Results in the kernel sending a SIGSYS signal to the triggering
+	task without executing the system call.  The kernel will
+	rollback the register state to just before the system call
+	entry such that a signal handler in the task will be able to
+	inspect the ucontext_t->uc_mcontext registers and emulate
+	system call success or failure upon return from the signal
+	handler.
+
+	The SECCOMP_RET_DATA portion of the return value will be passed
+	as si_errno.
+
+	SIGSYS triggered by seccomp will have a si_code of SYS_SECCOMP.
+
+SECCOMP_RET_ERRNO:
+	Results in the lower 16-bits of the return value being passed
+	to userland as the errno without executing the system call.
+
+SECCOMP_RET_TRACE:
+	When returned, this value will cause the kernel to attempt to
+	notify a ptrace()-based tracer prior to executing the system
+	call.  If there is no tracer present, -ENOSYS is returned to
+	userland and the system call is not executed.
+
+	A tracer will be notified if it requests PTRACE_O_TRACESECCOMP
+	using ptrace(PTRACE_SETOPTIONS).  The tracer will be notified
+	of a PTRACE_EVENT_SECCOMP and the SECCOMP_RET_DATA portion of
+	the BPF program return value will be available to the tracer
+	via PTRACE_GETEVENTMSG.
+
+SECCOMP_RET_ALLOW:
+	Results in the system call being executed.
+
+If multiple filters exist, the return value for the evaluation of a
+given system call will always use the highest precedent value.
+
+Precedence is only determined using the SECCOMP_RET_ACTION mask.  When
+multiple filters return values of the same precedence, only the
+SECCOMP_RET_DATA from the most recently installed filter will be
+returned.
+
+
+Example
+-------
+
+The samples/seccomp/ directory contains both an x86-specific example
+and a more generic example of a higher level macro interface for BPF
+program generation.
+
+Adding architecture support
+-----------------------
+
+See arch/Kconfig for the authoritative requirements.  In general, if an
+architecture supports both ptrace_event and seccomp, it will be able to
+support seccomp filter with minor fixup: SIGSYS support and seccomp return
+value checking.  Then it must just add CONFIG_HAVE_ARCH_SECCOMP_FILTER
+to its arch-specific Kconfig.
diff --git a/samples/Makefile b/samples/Makefile
index 6280817..f29b19c 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -1,4 +1,4 @@
 # Makefile for Linux samples code
 
 obj-$(CONFIG_SAMPLES)	+= kobject/ kprobes/ tracepoints/ trace_events/ \
-			   hw_breakpoint/ kfifo/ kdb/ hidraw/
+			   hw_breakpoint/ kfifo/ kdb/ hidraw/ seccomp/
diff --git a/samples/seccomp/Makefile b/samples/seccomp/Makefile
new file mode 100644
index 0000000..e8fe0f5
--- /dev/null
+++ b/samples/seccomp/Makefile
@@ -0,0 +1,38 @@
+# kbuild trick to avoid linker error. Can be omitted if a module is built.
+obj- := dummy.o
+
+hostprogs-$(CONFIG_SECCOMP) := bpf-fancy dropper
+bpf-fancy-objs := bpf-fancy.o bpf-helper.o
+
+HOSTCFLAGS_bpf-fancy.o += -I$(objtree)/usr/include
+HOSTCFLAGS_bpf-fancy.o += -idirafter $(objtree)/include
+HOSTCFLAGS_bpf-helper.o += -I$(objtree)/usr/include
+HOSTCFLAGS_bpf-helper.o += -idirafter $(objtree)/include
+
+HOSTCFLAGS_dropper.o += -I$(objtree)/usr/include
+HOSTCFLAGS_dropper.o += -idirafter $(objtree)/include
+dropper-objs := dropper.o
+
+# bpf-direct.c is x86-only.
+ifeq ($(SRCARCH),x86)
+# List of programs to build
+hostprogs-$(CONFIG_SECCOMP) += bpf-direct
+bpf-direct-objs := bpf-direct.o
+endif
+
+HOSTCFLAGS_bpf-direct.o += -I$(objtree)/usr/include
+HOSTCFLAGS_bpf-direct.o += -idirafter $(objtree)/include
+
+# Try to match the kernel target.
+ifeq ($(CONFIG_64BIT),)
+HOSTCFLAGS_bpf-direct.o += -m32
+HOSTCFLAGS_dropper.o += -m32
+HOSTCFLAGS_bpf-helper.o += -m32
+HOSTCFLAGS_bpf-fancy.o += -m32
+HOSTLOADLIBES_bpf-direct += -m32
+HOSTLOADLIBES_bpf-fancy += -m32
+HOSTLOADLIBES_dropper += -m32
+endif
+
+# Tell kbuild to always build the programs
+always := $(hostprogs-y)
diff --git a/samples/seccomp/bpf-direct.c b/samples/seccomp/bpf-direct.c
new file mode 100644
index 0000000..f1567ad
--- /dev/null
+++ b/samples/seccomp/bpf-direct.c
@@ -0,0 +1,176 @@
+/*
+ * Seccomp filter example for x86 (32-bit and 64-bit) with BPF macros
+ *
+ * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>
+ * Author: Will Drewry <wad@chromium.org>
+ *
+ * The code may be used by anyone for any purpose,
+ * and can serve as a starting point for developing
+ * applications using prctl(PR_SET_SECCOMP, 2, ...).
+ */
+#define __USE_GNU 1
+#define _GNU_SOURCE 1
+
+#include <linux/types.h>
+#include <linux/filter.h>
+#include <linux/seccomp.h>
+#include <linux/unistd.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stddef.h>
+#include <string.h>
+#include <sys/prctl.h>
+#include <unistd.h>
+
+#define syscall_arg(_n) (offsetof(struct seccomp_data, args[_n]))
+#define syscall_nr (offsetof(struct seccomp_data, nr))
+
+#if defined(__i386__)
+#define REG_RESULT	REG_EAX
+#define REG_SYSCALL	REG_EAX
+#define REG_ARG0	REG_EBX
+#define REG_ARG1	REG_ECX
+#define REG_ARG2	REG_EDX
+#define REG_ARG3	REG_ESI
+#define REG_ARG4	REG_EDI
+#define REG_ARG5	REG_EBP
+#elif defined(__x86_64__)
+#define REG_RESULT	REG_RAX
+#define REG_SYSCALL	REG_RAX
+#define REG_ARG0	REG_RDI
+#define REG_ARG1	REG_RSI
+#define REG_ARG2	REG_RDX
+#define REG_ARG3	REG_R10
+#define REG_ARG4	REG_R8
+#define REG_ARG5	REG_R9
+#else
+#error Unsupported platform
+#endif
+
+#ifndef PR_SET_NO_NEW_PRIVS
+#define PR_SET_NO_NEW_PRIVS 36
+#endif
+
+#ifndef SYS_SECCOMP
+#define SYS_SECCOMP 1
+#endif
+
+static void emulator(int nr, siginfo_t *info, void *void_context)
+{
+	ucontext_t *ctx = (ucontext_t *)(void_context);
+	int syscall;
+	char *buf;
+	ssize_t bytes;
+	size_t len;
+	if (info->si_code != SYS_SECCOMP)
+		return;
+	if (!ctx)
+		return;
+	syscall = ctx->uc_mcontext.gregs[REG_SYSCALL];
+	buf = (char *) ctx->uc_mcontext.gregs[REG_ARG1];
+	len = (size_t) ctx->uc_mcontext.gregs[REG_ARG2];
+
+	if (syscall != __NR_write)
+		return;
+	if (ctx->uc_mcontext.gregs[REG_ARG0] != STDERR_FILENO)
+		return;
+	/* Redirect stderr messages to stdout. Doesn't handle EINTR, etc */
+	ctx->uc_mcontext.gregs[REG_RESULT] = -1;
+	if (write(STDOUT_FILENO, "[ERR] ", 6) > 0) {
+		bytes = write(STDOUT_FILENO, buf, len);
+		ctx->uc_mcontext.gregs[REG_RESULT] = bytes;
+	}
+	return;
+}
+
+static int install_emulator(void)
+{
+	struct sigaction act;
+	sigset_t mask;
+	memset(&act, 0, sizeof(act));
+	sigemptyset(&mask);
+	sigaddset(&mask, SIGSYS);
+
+	act.sa_sigaction = &emulator;
+	act.sa_flags = SA_SIGINFO;
+	if (sigaction(SIGSYS, &act, NULL) < 0) {
+		perror("sigaction");
+		return -1;
+	}
+	if (sigprocmask(SIG_UNBLOCK, &mask, NULL)) {
+		perror("sigprocmask");
+		return -1;
+	}
+	return 0;
+}
+
+static int install_filter(void)
+{
+	struct sock_filter filter[] = {
+		/* Grab the system call number */
+		BPF_STMT(BPF_LD+BPF_W+BPF_ABS, syscall_nr),
+		/* Jump table for the allowed syscalls */
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_rt_sigreturn, 0, 1),
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
+#ifdef __NR_sigreturn
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_sigreturn, 0, 1),
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
+#endif
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_exit_group, 0, 1),
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_exit, 0, 1),
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_read, 1, 0),
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_write, 3, 2),
+
+		/* Check that read is only using stdin. */
+		BPF_STMT(BPF_LD+BPF_W+BPF_ABS, syscall_arg(0)),
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, STDIN_FILENO, 4, 0),
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL),
+
+		/* Check that write is only using stdout */
+		BPF_STMT(BPF_LD+BPF_W+BPF_ABS, syscall_arg(0)),
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, STDOUT_FILENO, 1, 0),
+		/* Trap attempts to write to stderr */
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, STDERR_FILENO, 1, 2),
+
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_TRAP),
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL),
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)(sizeof(filter)/sizeof(filter[0])),
+		.filter = filter,
+	};
+
+	if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
+		perror("prctl(NO_NEW_PRIVS)");
+		return 1;
+	}
+
+
+	if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog)) {
+		perror("prctl");
+		return 1;
+	}
+	return 0;
+}
+
+#define payload(_c) (_c), sizeof((_c))
+int main(int argc, char **argv)
+{
+	char buf[4096];
+	ssize_t bytes = 0;
+	if (install_emulator())
+		return 1;
+	if (install_filter())
+		return 1;
+	syscall(__NR_write, STDOUT_FILENO,
+		payload("OHAI! WHAT IS YOUR NAME? "));
+	bytes = syscall(__NR_read, STDIN_FILENO, buf, sizeof(buf));
+	syscall(__NR_write, STDOUT_FILENO, payload("HELLO, "));
+	syscall(__NR_write, STDOUT_FILENO, buf, bytes);
+	syscall(__NR_write, STDERR_FILENO,
+		payload("Error message going to STDERR\n"));
+	return 0;
+}
diff --git a/samples/seccomp/bpf-fancy.c b/samples/seccomp/bpf-fancy.c
new file mode 100644
index 0000000..bf1f6b5
--- /dev/null
+++ b/samples/seccomp/bpf-fancy.c
@@ -0,0 +1,102 @@
+/*
+ * Seccomp BPF example using a macro-based generator.
+ *
+ * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>
+ * Author: Will Drewry <wad@chromium.org>
+ *
+ * The code may be used by anyone for any purpose,
+ * and can serve as a starting point for developing
+ * applications using prctl(PR_ATTACH_SECCOMP_FILTER).
+ */
+
+#include <linux/filter.h>
+#include <linux/seccomp.h>
+#include <linux/unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/prctl.h>
+#include <unistd.h>
+
+#include "bpf-helper.h"
+
+#ifndef PR_SET_NO_NEW_PRIVS
+#define PR_SET_NO_NEW_PRIVS 36
+#endif
+
+int main(int argc, char **argv)
+{
+	struct bpf_labels l;
+	static const char msg1[] = "Please type something: ";
+	static const char msg2[] = "You typed: ";
+	char buf[256];
+	struct sock_filter filter[] = {
+		/* TODO: LOAD_SYSCALL_NR(arch) and enforce an arch */
+		LOAD_SYSCALL_NR,
+		SYSCALL(__NR_exit, ALLOW),
+		SYSCALL(__NR_exit_group, ALLOW),
+		SYSCALL(__NR_write, JUMP(&l, write_fd)),
+		SYSCALL(__NR_read, JUMP(&l, read)),
+		DENY,  /* Don't passthrough into a label */
+
+		LABEL(&l, read),
+		ARG(0),
+		JNE(STDIN_FILENO, DENY),
+		ARG(1),
+		JNE((unsigned long)buf, DENY),
+		ARG(2),
+		JGE(sizeof(buf), DENY),
+		ALLOW,
+
+		LABEL(&l, write_fd),
+		ARG(0),
+		JEQ(STDOUT_FILENO, JUMP(&l, write_buf)),
+		JEQ(STDERR_FILENO, JUMP(&l, write_buf)),
+		DENY,
+
+		LABEL(&l, write_buf),
+		ARG(1),
+		JEQ((unsigned long)msg1, JUMP(&l, msg1_len)),
+		JEQ((unsigned long)msg2, JUMP(&l, msg2_len)),
+		JEQ((unsigned long)buf, JUMP(&l, buf_len)),
+		DENY,
+
+		LABEL(&l, msg1_len),
+		ARG(2),
+		JLT(sizeof(msg1), ALLOW),
+		DENY,
+
+		LABEL(&l, msg2_len),
+		ARG(2),
+		JLT(sizeof(msg2), ALLOW),
+		DENY,
+
+		LABEL(&l, buf_len),
+		ARG(2),
+		JLT(sizeof(buf), ALLOW),
+		DENY,
+	};
+	struct sock_fprog prog = {
+		.filter = filter,
+		.len = (unsigned short)(sizeof(filter)/sizeof(filter[0])),
+	};
+	ssize_t bytes;
+	bpf_resolve_jumps(&l, filter, sizeof(filter)/sizeof(*filter));
+
+	if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
+		perror("prctl(NO_NEW_PRIVS)");
+		return 1;
+	}
+
+	if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog)) {
+		perror("prctl(SECCOMP)");
+		return 1;
+	}
+	syscall(__NR_write, STDOUT_FILENO, msg1, strlen(msg1));
+	bytes = syscall(__NR_read, STDIN_FILENO, buf, sizeof(buf)-1);
+	bytes = (bytes > 0 ? bytes : 0);
+	syscall(__NR_write, STDERR_FILENO, msg2, strlen(msg2));
+	syscall(__NR_write, STDERR_FILENO, buf, bytes);
+	/* Now get killed */
+	syscall(__NR_write, STDERR_FILENO, msg2, strlen(msg2)+2);
+	return 0;
+}
diff --git a/samples/seccomp/bpf-helper.c b/samples/seccomp/bpf-helper.c
new file mode 100644
index 0000000..579cfe3
--- /dev/null
+++ b/samples/seccomp/bpf-helper.c
@@ -0,0 +1,89 @@
+/*
+ * Seccomp BPF helper functions
+ *
+ * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>
+ * Author: Will Drewry <wad@chromium.org>
+ *
+ * The code may be used by anyone for any purpose,
+ * and can serve as a starting point for developing
+ * applications using prctl(PR_ATTACH_SECCOMP_FILTER).
+ */
+
+#include <stdio.h>
+#include <string.h>
+
+#include "bpf-helper.h"
+
+int bpf_resolve_jumps(struct bpf_labels *labels,
+		      struct sock_filter *filter, size_t count)
+{
+	struct sock_filter *begin = filter;
+	__u8 insn = count - 1;
+
+	if (count < 1)
+		return -1;
+	/*
+	* Walk it once, backwards, to build the label table and do fixups.
+	* Since backward jumps are disallowed by BPF, this is easy.
+	*/
+	filter += insn;
+	for (; filter >= begin; --insn, --filter) {
+		if (filter->code != (BPF_JMP+BPF_JA))
+			continue;
+		switch ((filter->jt<<8)|filter->jf) {
+		case (JUMP_JT<<8)|JUMP_JF:
+			if (labels->labels[filter->k].location == 0xffffffff) {
+				fprintf(stderr, "Unresolved label: '%s'\n",
+					labels->labels[filter->k].label);
+				return 1;
+			}
+			filter->k = labels->labels[filter->k].location -
+				    (insn + 1);
+			filter->jt = 0;
+			filter->jf = 0;
+			continue;
+		case (LABEL_JT<<8)|LABEL_JF:
+			if (labels->labels[filter->k].location != 0xffffffff) {
+				fprintf(stderr, "Duplicate label use: '%s'\n",
+					labels->labels[filter->k].label);
+				return 1;
+			}
+			labels->labels[filter->k].location = insn;
+			filter->k = 0; /* fall through */
+			filter->jt = 0;
+			filter->jf = 0;
+			continue;
+		}
+	}
+	return 0;
+}
+
+/* Simple lookup table for labels. */
+__u32 seccomp_bpf_label(struct bpf_labels *labels, const char *label)
+{
+	struct __bpf_label *begin = labels->labels, *end;
+	int id;
+	if (labels->count == 0) {
+		begin->label = label;
+		begin->location = 0xffffffff;
+		labels->count++;
+		return 0;
+	}
+	end = begin + labels->count;
+	for (id = 0; begin < end; ++begin, ++id) {
+		if (!strcmp(label, begin->label))
+			return id;
+	}
+	begin->label = label;
+	begin->location = 0xffffffff;
+	labels->count++;
+	return id;
+}
+
+void seccomp_bpf_print(struct sock_filter *filter, size_t count)
+{
+	struct sock_filter *end = filter + count;
+	for ( ; filter < end; ++filter)
+		printf("{ code=%u,jt=%u,jf=%u,k=%u },\n",
+			filter->code, filter->jt, filter->jf, filter->k);
+}
diff --git a/samples/seccomp/bpf-helper.h b/samples/seccomp/bpf-helper.h
new file mode 100644
index 0000000..643279d
--- /dev/null
+++ b/samples/seccomp/bpf-helper.h
@@ -0,0 +1,238 @@
+/*
+ * Example wrapper around BPF macros.
+ *
+ * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>
+ * Author: Will Drewry <wad@chromium.org>
+ *
+ * The code may be used by anyone for any purpose,
+ * and can serve as a starting point for developing
+ * applications using prctl(PR_SET_SECCOMP, 2, ...).
+ *
+ * No guarantees are provided with respect to the correctness
+ * or functionality of this code.
+ */
+#ifndef __BPF_HELPER_H__
+#define __BPF_HELPER_H__
+
+#include <asm/bitsperlong.h>	/* for __BITS_PER_LONG */
+#include <endian.h>
+#include <linux/filter.h>
+#include <linux/seccomp.h>	/* for seccomp_data */
+#include <linux/types.h>
+#include <linux/unistd.h>
+#include <stddef.h>
+
+#define BPF_LABELS_MAX 256
+struct bpf_labels {
+	int count;
+	struct __bpf_label {
+		const char *label;
+		__u32 location;
+	} labels[BPF_LABELS_MAX];
+};
+
+int bpf_resolve_jumps(struct bpf_labels *labels,
+		      struct sock_filter *filter, size_t count);
+__u32 seccomp_bpf_label(struct bpf_labels *labels, const char *label);
+void seccomp_bpf_print(struct sock_filter *filter, size_t count);
+
+#define JUMP_JT 0xff
+#define JUMP_JF 0xff
+#define LABEL_JT 0xfe
+#define LABEL_JF 0xfe
+
+#define ALLOW \
+	BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW)
+#define DENY \
+	BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL)
+#define JUMP(labels, label) \
+	BPF_JUMP(BPF_JMP+BPF_JA, FIND_LABEL((labels), (label)), \
+		 JUMP_JT, JUMP_JF)
+#define LABEL(labels, label) \
+	BPF_JUMP(BPF_JMP+BPF_JA, FIND_LABEL((labels), (label)), \
+		 LABEL_JT, LABEL_JF)
+#define SYSCALL(nr, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (nr), 0, 1), \
+	jt
+
+/* Lame, but just an example */
+#define FIND_LABEL(labels, label) seccomp_bpf_label((labels), #label)
+
+#define EXPAND(...) __VA_ARGS__
+/* Map all width-sensitive operations */
+#if __BITS_PER_LONG == 32
+
+#define JEQ(x, jt) JEQ32(x, EXPAND(jt))
+#define JNE(x, jt) JNE32(x, EXPAND(jt))
+#define JGT(x, jt) JGT32(x, EXPAND(jt))
+#define JLT(x, jt) JLT32(x, EXPAND(jt))
+#define JGE(x, jt) JGE32(x, EXPAND(jt))
+#define JLE(x, jt) JLE32(x, EXPAND(jt))
+#define JA(x, jt) JA32(x, EXPAND(jt))
+#define ARG(i) ARG_32(i)
+#define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)])
+
+#elif __BITS_PER_LONG == 64
+
+/* Ensure that we load the logically correct offset. */
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+#define ENDIAN(_lo, _hi) _lo, _hi
+#define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)])
+#define HI_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) + sizeof(__u32)
+#elif __BYTE_ORDER == __BIG_ENDIAN
+#define ENDIAN(_lo, _hi) _hi, _lo
+#define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) + sizeof(__u32)
+#define HI_ARG(idx) offsetof(struct seccomp_data, args[(idx)])
+#else
+#error "Unknown endianness"
+#endif
+
+union arg64 {
+	struct {
+		__u32 ENDIAN(lo32, hi32);
+	};
+	__u64 u64;
+};
+
+#define JEQ(x, jt) \
+	JEQ64(((union arg64){.u64 = (x)}).lo32, \
+	      ((union arg64){.u64 = (x)}).hi32, \
+	      EXPAND(jt))
+#define JGT(x, jt) \
+	JGT64(((union arg64){.u64 = (x)}).lo32, \
+	      ((union arg64){.u64 = (x)}).hi32, \
+	      EXPAND(jt))
+#define JGE(x, jt) \
+	JGE64(((union arg64){.u64 = (x)}).lo32, \
+	      ((union arg64){.u64 = (x)}).hi32, \
+	      EXPAND(jt))
+#define JNE(x, jt) \
+	JNE64(((union arg64){.u64 = (x)}).lo32, \
+	      ((union arg64){.u64 = (x)}).hi32, \
+	      EXPAND(jt))
+#define JLT(x, jt) \
+	JLT64(((union arg64){.u64 = (x)}).lo32, \
+	      ((union arg64){.u64 = (x)}).hi32, \
+	      EXPAND(jt))
+#define JLE(x, jt) \
+	JLE64(((union arg64){.u64 = (x)}).lo32, \
+	      ((union arg64){.u64 = (x)}).hi32, \
+	      EXPAND(jt))
+
+#define JA(x, jt) \
+	JA64(((union arg64){.u64 = (x)}).lo32, \
+	       ((union arg64){.u64 = (x)}).hi32, \
+	       EXPAND(jt))
+#define ARG(i) ARG_64(i)
+
+#else
+#error __BITS_PER_LONG value unusable.
+#endif
+
+/* Loads the arg into A */
+#define ARG_32(idx) \
+	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, LO_ARG(idx))
+
+/* Loads hi into A and lo in X */
+#define ARG_64(idx) \
+	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, LO_ARG(idx)), \
+	BPF_STMT(BPF_ST, 0), /* lo -> M[0] */ \
+	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, HI_ARG(idx)), \
+	BPF_STMT(BPF_ST, 1) /* hi -> M[1] */
+
+#define JEQ32(value, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (value), 0, 1), \
+	jt
+
+#define JNE32(value, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (value), 1, 0), \
+	jt
+
+/* Checks the lo, then swaps to check the hi. A=lo,X=hi */
+#define JEQ64(lo, hi, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
+	BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 0, 2), \
+	BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+	jt, \
+	BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+
+#define JNE64(lo, hi, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 5, 0), \
+	BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 2, 0), \
+	BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+	jt, \
+	BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+
+#define JA32(value, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (value), 0, 1), \
+	jt
+
+#define JA64(lo, hi, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (hi), 3, 0), \
+	BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+	BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (lo), 0, 2), \
+	BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+	jt, \
+	BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+
+#define JGE32(value, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 0, 1), \
+	jt
+
+#define JLT32(value, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 1, 0), \
+	jt
+
+/* Shortcut checking if hi > arg.hi. */
+#define JGE64(lo, hi, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
+	BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+	BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (lo), 0, 2), \
+	BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+	jt, \
+	BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+
+#define JLT64(lo, hi, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (hi), 0, 4), \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
+	BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+	BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 2, 0), \
+	BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+	jt, \
+	BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+
+#define JGT32(value, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 0, 1), \
+	jt
+
+#define JLE32(value, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 1, 0), \
+	jt
+
+/* Check hi > args.hi first, then do the GE checking */
+#define JGT64(lo, hi, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
+	BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+	BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 0, 2), \
+	BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+	jt, \
+	BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+
+#define JLE64(lo, hi, jt) \
+	BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 6, 0), \
+	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 3), \
+	BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+	BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 2, 0), \
+	BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+	jt, \
+	BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+
+#define LOAD_SYSCALL_NR \
+	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
+		 offsetof(struct seccomp_data, nr))
+
+#endif  /* __BPF_HELPER_H__ */
diff --git a/samples/seccomp/dropper.c b/samples/seccomp/dropper.c
new file mode 100644
index 0000000..c69c347
--- /dev/null
+++ b/samples/seccomp/dropper.c
@@ -0,0 +1,68 @@
+/*
+ * Naive system call dropper built on seccomp_filter.
+ *
+ * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>
+ * Author: Will Drewry <wad@chromium.org>
+ *
+ * The code may be used by anyone for any purpose,
+ * and can serve as a starting point for developing
+ * applications using prctl(PR_SET_SECCOMP, 2, ...).
+ *
+ * When run, returns the specified errno for the specified
+ * system call number against the given architecture.
+ *
+ * Run this one as root as PR_SET_NO_NEW_PRIVS is not called.
+ */
+
+#include <errno.h>
+#include <linux/audit.h>
+#include <linux/filter.h>
+#include <linux/seccomp.h>
+#include <linux/unistd.h>
+#include <stdio.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <sys/prctl.h>
+#include <unistd.h>
+
+static int install_filter(int nr, int arch, int error)
+{
+	struct sock_filter filter[] = {
+		BPF_STMT(BPF_LD+BPF_W+BPF_ABS,
+			 (offsetof(struct seccomp_data, arch))),
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, arch, 0, 3),
+		BPF_STMT(BPF_LD+BPF_W+BPF_ABS,
+			 (offsetof(struct seccomp_data, nr))),
+		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, nr, 0, 1),
+		BPF_STMT(BPF_RET+BPF_K,
+			 SECCOMP_RET_ERRNO|(error & SECCOMP_RET_DATA)),
+		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
+	};
+	struct sock_fprog prog = {
+		.len = (unsigned short)(sizeof(filter)/sizeof(filter[0])),
+		.filter = filter,
+	};
+	if (prctl(PR_SET_SECCOMP, 2, &prog)) {
+		perror("prctl");
+		return 1;
+	}
+	return 0;
+}
+
+int main(int argc, char **argv)
+{
+	if (argc < 5) {
+		fprintf(stderr, "Usage:\n"
+			"dropper <syscall_nr> <arch> <errno> <prog> [<args>]\n"
+			"Hint:	AUDIT_ARCH_I386: 0x%X\n"
+			"	AUDIT_ARCH_X86_64: 0x%X\n"
+			"\n", AUDIT_ARCH_I386, AUDIT_ARCH_X86_64);
+		return 1;
+	}
+	if (install_filter(strtol(argv[1], NULL, 0), strtol(argv[2], NULL, 0),
+			   strtol(argv[3], NULL, 0)))
+		return 1;
+	execv(argv[4], &argv[4]);
+	printf("Failed to execv\n");
+	return 255;
+}
-- 
1.7.5.4

Re: [PATCH v15 11/13] ptrace,seccomp: Add PTRACE_SECCOMP support

[Indan Zupancic]

Hi Will,

On Thu, March 15, 2012 04:12, Will Drewry wrote:
> @@ -73,6 +74,7 @@
>  #define PTRACE_EVENT_VFORK_DONE	5
>  #define PTRACE_EVENT_EXIT	6
>  #define PTRACE_EVENT_STOP	7
> +#define PTRACE_EVENT_SECCOMP	8
>
>  #include <asm/ptrace.h>
>
> @@ -101,8 +103,9 @@
>  #define PT_TRACE_EXEC		PT_EVENT_FLAG(PTRACE_EVENT_EXEC)
>  #define PT_TRACE_VFORK_DONE	PT_EVENT_FLAG(PTRACE_EVENT_VFORK_DONE)
>  #define PT_TRACE_EXIT		PT_EVENT_FLAG(PTRACE_EVENT_EXIT)
> +#define PT_TRACE_SECCOMP	PT_EVENT_FLAG(PTRACE_EVENT_SECCOMP)
>
> -#define PT_TRACE_MASK	0x000003f4
> +#define PT_TRACE_MASK	0x00000ff4

Did you miss this bit?

Greetings,

Indan

Re: [PATCH v15 11/13] ptrace,seccomp: Add PTRACE_SECCOMP support

[Indan Zupancic]

Hi Will,

On Thu, March 15, 2012 04:12, Will Drewry wrote:
> @@ -73,6 +74,7 @@
>  #define PTRACE_EVENT_VFORK_DONE	5
>  #define PTRACE_EVENT_EXIT	6
>  #define PTRACE_EVENT_STOP	7
> +#define PTRACE_EVENT_SECCOMP	8
>
>  #include <asm/ptrace.h>
>
> @@ -101,8 +103,9 @@
>  #define PT_TRACE_EXEC		PT_EVENT_FLAG(PTRACE_EVENT_EXEC)
>  #define PT_TRACE_VFORK_DONE	PT_EVENT_FLAG(PTRACE_EVENT_VFORK_DONE)
>  #define PT_TRACE_EXIT		PT_EVENT_FLAG(PTRACE_EVENT_EXIT)
> +#define PT_TRACE_SECCOMP	PT_EVENT_FLAG(PTRACE_EVENT_SECCOMP)
>
> -#define PT_TRACE_MASK	0x000003f4
> +#define PT_TRACE_MASK	0x00000ff4

Did you miss this bit?

Greetings,

Indan

Re: [PATCH v15 11/13] ptrace,seccomp: Add PTRACE_SECCOMP support

[Indan Zupancic]

Hi Will,

On Thu, March 15, 2012 04:12, Will Drewry wrote:
> @@ -73,6 +74,7 @@
>  #define PTRACE_EVENT_VFORK_DONE	5
>  #define PTRACE_EVENT_EXIT	6
>  #define PTRACE_EVENT_STOP	7
> +#define PTRACE_EVENT_SECCOMP	8
>
>  #include <asm/ptrace.h>
>
> @@ -101,8 +103,9 @@
>  #define PT_TRACE_EXEC		PT_EVENT_FLAG(PTRACE_EVENT_EXEC)
>  #define PT_TRACE_VFORK_DONE	PT_EVENT_FLAG(PTRACE_EVENT_VFORK_DONE)
>  #define PT_TRACE_EXIT		PT_EVENT_FLAG(PTRACE_EVENT_EXIT)
> +#define PT_TRACE_SECCOMP	PT_EVENT_FLAG(PTRACE_EVENT_SECCOMP)
>
> -#define PT_TRACE_MASK	0x000003f4
> +#define PT_TRACE_MASK	0x00000ff4

Did you miss this bit?

Greetings,

Indan

[kernel-hardening] Re: [PATCH v15 11/13] ptrace,seccomp: Add PTRACE_SECCOMP support

[Indan Zupancic]

Hi Will,

On Thu, March 15, 2012 04:12, Will Drewry wrote:
> @@ -73,6 +74,7 @@
>  #define PTRACE_EVENT_VFORK_DONE	5
>  #define PTRACE_EVENT_EXIT	6
>  #define PTRACE_EVENT_STOP	7
> +#define PTRACE_EVENT_SECCOMP	8
>
>  #include <asm/ptrace.h>
>
> @@ -101,8 +103,9 @@
>  #define PT_TRACE_EXEC		PT_EVENT_FLAG(PTRACE_EVENT_EXEC)
>  #define PT_TRACE_VFORK_DONE	PT_EVENT_FLAG(PTRACE_EVENT_VFORK_DONE)
>  #define PT_TRACE_EXIT		PT_EVENT_FLAG(PTRACE_EVENT_EXIT)
> +#define PT_TRACE_SECCOMP	PT_EVENT_FLAG(PTRACE_EVENT_SECCOMP)
>
> -#define PT_TRACE_MASK	0x000003f4
> +#define PT_TRACE_MASK	0x00000ff4

Did you miss this bit?

Greetings,

Indan

Re: [PATCH v15 11/13] ptrace,seccomp: Add PTRACE_SECCOMP support

[Will Drewry]

On Wed, Mar 14, 2012 at 11:49 PM, Indan Zupancic <indan@nul.nu> wrote:
> Hi Will,
>
> On Thu, March 15, 2012 04:12, Will Drewry wrote:
>> @@ -73,6 +74,7 @@
>>  #define PTRACE_EVENT_VFORK_DONE      5
>>  #define PTRACE_EVENT_EXIT    6
>>  #define PTRACE_EVENT_STOP    7
>> +#define PTRACE_EVENT_SECCOMP 8
>>
>>  #include <asm/ptrace.h>
>>
>> @@ -101,8 +103,9 @@
>>  #define PT_TRACE_EXEC                PT_EVENT_FLAG(PTRACE_EVENT_EXEC)
>>  #define PT_TRACE_VFORK_DONE  PT_EVENT_FLAG(PTRACE_EVENT_VFORK_DONE)
>>  #define PT_TRACE_EXIT                PT_EVENT_FLAG(PTRACE_EVENT_EXIT)
>> +#define PT_TRACE_SECCOMP     PT_EVENT_FLAG(PTRACE_EVENT_SECCOMP)
>>
>> -#define PT_TRACE_MASK        0x000003f4
>> +#define PT_TRACE_MASK        0x00000ff4
>
> Did you miss this bit?

Kinda.  I'll go ahead and switch it to 0xbf4, but PT_TRACE_MASK
doesn't exist in linux-next so this bit disappears on merge.  However,
it is relevant if people are backporting this code, so I'll push a new
rev of it in a bit if I don't get any other comments (or include it in
the next rev if there are comments).

Thanks!
will

[kernel-hardening] Re: [PATCH v15 11/13] ptrace,seccomp: Add PTRACE_SECCOMP support

[Will Drewry]

On Wed, Mar 14, 2012 at 11:49 PM, Indan Zupancic <indan@nul.nu> wrote:
> Hi Will,
>
> On Thu, March 15, 2012 04:12, Will Drewry wrote:
>> @@ -73,6 +74,7 @@
>>  #define PTRACE_EVENT_VFORK_DONE      5
>>  #define PTRACE_EVENT_EXIT    6
>>  #define PTRACE_EVENT_STOP    7
>> +#define PTRACE_EVENT_SECCOMP 8
>>
>>  #include <asm/ptrace.h>
>>
>> @@ -101,8 +103,9 @@
>>  #define PT_TRACE_EXEC                PT_EVENT_FLAG(PTRACE_EVENT_EXEC)
>>  #define PT_TRACE_VFORK_DONE  PT_EVENT_FLAG(PTRACE_EVENT_VFORK_DONE)
>>  #define PT_TRACE_EXIT                PT_EVENT_FLAG(PTRACE_EVENT_EXIT)
>> +#define PT_TRACE_SECCOMP     PT_EVENT_FLAG(PTRACE_EVENT_SECCOMP)
>>
>> -#define PT_TRACE_MASK        0x000003f4
>> +#define PT_TRACE_MASK        0x00000ff4
>
> Did you miss this bit?

Kinda.  I'll go ahead and switch it to 0xbf4, but PT_TRACE_MASK
doesn't exist in linux-next so this bit disappears on merge.  However,
it is relevant if people are backporting this code, so I'll push a new
rev of it in a bit if I don't get any other comments (or include it in
the next rev if there are comments).

Thanks!
will

Re: [PATCH v15 01/13] sk_run_filter: add BPF_S_ANC_SECCOMP_LD_W

[Eric Dumazet]

On Wed, 2012-03-14 at 22:11 -0500, Will Drewry wrote:
> Introduces a new BPF ancillary instruction that all LD calls will be
> mapped through when skb_run_filter() is being used for seccomp BPF.  The
> rewriting will be done using a secondary chk_filter function that is run
> after skb_chk_filter.
> 
> The code change is guarded by CONFIG_SECCOMP_FILTER which is added,
> along with the seccomp_bpf_load() function later in this series.
> 
> This is based on http://lkml.org/lkml/2012/3/2/141
> 
> v15: include seccomp.h explicitly for when seccomp_bpf_load exists.
> v14: First cut using a single additional instruction
> ... v13: made bpf functions generic.
> 
> Suggested-by: Indan Zupancic <indan@nul.nu>
> Signed-off-by: Will Drewry <wad@chromium.org>
> ---
>  include/linux/filter.h |    1 +
>  net/core/filter.c      |    6 ++++++
>  2 files changed, 7 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/filter.h b/include/linux/filter.h
> index 8eeb205..aaa2e80 100644
> --- a/include/linux/filter.h
> +++ b/include/linux/filter.h
> @@ -228,6 +228,7 @@ enum {
>  	BPF_S_ANC_HATYPE,
>  	BPF_S_ANC_RXHASH,
>  	BPF_S_ANC_CPU,
> +	BPF_S_ANC_SECCOMP_LD_W,
>  };
>  
>  #endif /* __KERNEL__ */
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 5dea452..d775edc 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -39,6 +39,7 @@
>  #include <linux/filter.h>
>  #include <linux/reciprocal_div.h>
>  #include <linux/ratelimit.h>
> +#include <linux/seccomp.h>
>  
>  /* No hurry in this branch */
>  static void *__load_pointer(const struct sk_buff *skb, int k, unsigned int size)
> @@ -350,6 +351,11 @@ load_b:
>  				A = 0;
>  			continue;
>  		}
> +#ifdef CONFIG_SECCOMP_FILTER
> +		case BPF_S_ANC_SECCOMP_LD_W:
> +			A = seccomp_bpf_load(fentry->k);
> +			continue;
> +#endif
>  		default:
>  			WARN_RATELIMIT(1, "Unknown code:%u jt:%u tf:%u k:%u\n",
>  				       fentry->code, fentry->jt,


Acked-by: Eric Dumazet <eric.dumazet@gmail.com>

[kernel-hardening] Re: [PATCH v15 01/13] sk_run_filter: add BPF_S_ANC_SECCOMP_LD_W

[Eric Dumazet]

On Wed, 2012-03-14 at 22:11 -0500, Will Drewry wrote:
> Introduces a new BPF ancillary instruction that all LD calls will be
> mapped through when skb_run_filter() is being used for seccomp BPF.  The
> rewriting will be done using a secondary chk_filter function that is run
> after skb_chk_filter.
> 
> The code change is guarded by CONFIG_SECCOMP_FILTER which is added,
> along with the seccomp_bpf_load() function later in this series.
> 
> This is based on http://lkml.org/lkml/2012/3/2/141
> 
> v15: include seccomp.h explicitly for when seccomp_bpf_load exists.
> v14: First cut using a single additional instruction
> ... v13: made bpf functions generic.
> 
> Suggested-by: Indan Zupancic <indan@nul.nu>
> Signed-off-by: Will Drewry <wad@chromium.org>
> ---
>  include/linux/filter.h |    1 +
>  net/core/filter.c      |    6 ++++++
>  2 files changed, 7 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/filter.h b/include/linux/filter.h
> index 8eeb205..aaa2e80 100644
> --- a/include/linux/filter.h
> +++ b/include/linux/filter.h
> @@ -228,6 +228,7 @@ enum {
>  	BPF_S_ANC_HATYPE,
>  	BPF_S_ANC_RXHASH,
>  	BPF_S_ANC_CPU,
> +	BPF_S_ANC_SECCOMP_LD_W,
>  };
>  
>  #endif /* __KERNEL__ */
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 5dea452..d775edc 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -39,6 +39,7 @@
>  #include <linux/filter.h>
>  #include <linux/reciprocal_div.h>
>  #include <linux/ratelimit.h>
> +#include <linux/seccomp.h>
>  
>  /* No hurry in this branch */
>  static void *__load_pointer(const struct sk_buff *skb, int k, unsigned int size)
> @@ -350,6 +351,11 @@ load_b:
>  				A = 0;
>  			continue;
>  		}
> +#ifdef CONFIG_SECCOMP_FILTER
> +		case BPF_S_ANC_SECCOMP_LD_W:
> +			A = seccomp_bpf_load(fentry->k);
> +			continue;
> +#endif
>  		default:
>  			WARN_RATELIMIT(1, "Unknown code:%u jt:%u tf:%u k:%u\n",
>  				       fentry->code, fentry->jt,


Acked-by: Eric Dumazet <eric.dumazet@gmail.com>

Re: [PATCH v15 02/13] net/compat.c,linux/filter.h: share compat_sock_fprog

[Eric Dumazet]

On Wed, 2012-03-14 at 22:11 -0500, Will Drewry wrote:
> Any other users of bpf_*_filter that take a struct sock_fprog from
> userspace will need to be able to also accept a compat_sock_fprog
> if the arch supports compat calls.  This change let's the existing
> compat_sock_fprog be shared.
> 
> Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
> Signed-off-by: Will Drewry <wad@chromium.org>
> 
> v14: rebase/nochanges
> v13: rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
> v12: rebase on to linux-next
> v11: introduction
> ---
>  include/linux/filter.h |   11 +++++++++++
>  net/compat.c           |    8 --------
>  2 files changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/filter.h b/include/linux/filter.h
> index aaa2e80..f2e5315 100644
> --- a/include/linux/filter.h
> +++ b/include/linux/filter.h
> @@ -10,6 +10,7 @@
>  
>  #ifdef __KERNEL__
>  #include <linux/atomic.h>
> +#include <linux/compat.h>
>  #endif
>  
>  /*
> @@ -132,6 +133,16 @@ struct sock_fprog {	/* Required for SO_ATTACH_FILTER. */
>  
>  #ifdef __KERNEL__
>  
> +#ifdef CONFIG_COMPAT
> +/*
> + * A struct sock_filter is architecture independent.
> + */
> +struct compat_sock_fprog {
> +	u16		len;
> +	compat_uptr_t	filter;		/* struct sock_filter * */
> +};
> +#endif
> +
>  struct sk_buff;
>  struct sock;
>  
> diff --git a/net/compat.c b/net/compat.c
> index 6def90e..c5c61c8 100644
> --- a/net/compat.c
> +++ b/net/compat.c
> @@ -326,14 +326,6 @@ void scm_detach_fds_compat(struct msghdr *kmsg, struct scm_cookie *scm)
>  	__scm_destroy(scm);
>  }
>  
> -/*
> - * A struct sock_filter is architecture independent.
> - */
> -struct compat_sock_fprog {
> -	u16		len;
> -	compat_uptr_t	filter;		/* struct sock_filter * */
> -};
> -
>  static int do_set_attach_filter(struct socket *sock, int level, int optname,
>  				char __user *optval, unsigned int optlen)
>  {

Acked-by: Eric Dumazet <eric.dumazet@gmail.com>

[kernel-hardening] Re: [PATCH v15 02/13] net/compat.c,linux/filter.h: share compat_sock_fprog

[Eric Dumazet]

On Wed, 2012-03-14 at 22:11 -0500, Will Drewry wrote:
> Any other users of bpf_*_filter that take a struct sock_fprog from
> userspace will need to be able to also accept a compat_sock_fprog
> if the arch supports compat calls.  This change let's the existing
> compat_sock_fprog be shared.
> 
> Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
> Signed-off-by: Will Drewry <wad@chromium.org>
> 
> v14: rebase/nochanges
> v13: rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
> v12: rebase on to linux-next
> v11: introduction
> ---
>  include/linux/filter.h |   11 +++++++++++
>  net/compat.c           |    8 --------
>  2 files changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/filter.h b/include/linux/filter.h
> index aaa2e80..f2e5315 100644
> --- a/include/linux/filter.h
> +++ b/include/linux/filter.h
> @@ -10,6 +10,7 @@
>  
>  #ifdef __KERNEL__
>  #include <linux/atomic.h>
> +#include <linux/compat.h>
>  #endif
>  
>  /*
> @@ -132,6 +133,16 @@ struct sock_fprog {	/* Required for SO_ATTACH_FILTER. */
>  
>  #ifdef __KERNEL__
>  
> +#ifdef CONFIG_COMPAT
> +/*
> + * A struct sock_filter is architecture independent.
> + */
> +struct compat_sock_fprog {
> +	u16		len;
> +	compat_uptr_t	filter;		/* struct sock_filter * */
> +};
> +#endif
> +
>  struct sk_buff;
>  struct sock;
>  
> diff --git a/net/compat.c b/net/compat.c
> index 6def90e..c5c61c8 100644
> --- a/net/compat.c
> +++ b/net/compat.c
> @@ -326,14 +326,6 @@ void scm_detach_fds_compat(struct msghdr *kmsg, struct scm_cookie *scm)
>  	__scm_destroy(scm);
>  }
>  
> -/*
> - * A struct sock_filter is architecture independent.
> - */
> -struct compat_sock_fprog {
> -	u16		len;
> -	compat_uptr_t	filter;		/* struct sock_filter * */
> -};
> -
>  static int do_set_attach_filter(struct socket *sock, int level, int optname,
>  				char __user *optval, unsigned int optlen)
>  {

Acked-by: Eric Dumazet <eric.dumazet@gmail.com>

Re: [PATCH v15 02/13] net/compat.c,linux/filter.h: share compat_sock_fprog

[Will Drewry]

On Fri, Mar 16, 2012 at 1:16 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On Wed, 2012-03-14 at 22:11 -0500, Will Drewry wrote:
>> Any other users of bpf_*_filter that take a struct sock_fprog from
>> userspace will need to be able to also accept a compat_sock_fprog
>> if the arch supports compat calls.  This change let's the existing
>> compat_sock_fprog be shared.
>>
>> Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
>> Signed-off-by: Will Drewry <wad@chromium.org>
>>
>> v14: rebase/nochanges
>> v13: rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
>> v12: rebase on to linux-next
>> v11: introduction
>> ---
>>  include/linux/filter.h |   11 +++++++++++
>>  net/compat.c           |    8 --------
>>  2 files changed, 11 insertions(+), 8 deletions(-)
>>
>> diff --git a/include/linux/filter.h b/include/linux/filter.h
>> index aaa2e80..f2e5315 100644
>> --- a/include/linux/filter.h
>> +++ b/include/linux/filter.h
>> @@ -10,6 +10,7 @@
>>
>>  #ifdef __KERNEL__
>>  #include <linux/atomic.h>
>> +#include <linux/compat.h>
>>  #endif
>>
>>  /*
>> @@ -132,6 +133,16 @@ struct sock_fprog {      /* Required for SO_ATTACH_FILTER. */
>>
>>  #ifdef __KERNEL__
>>
>> +#ifdef CONFIG_COMPAT
>> +/*
>> + * A struct sock_filter is architecture independent.
>> + */
>> +struct compat_sock_fprog {
>> +     u16             len;
>> +     compat_uptr_t   filter;         /* struct sock_filter * */
>> +};
>> +#endif
>> +
>>  struct sk_buff;
>>  struct sock;
>>
>> diff --git a/net/compat.c b/net/compat.c
>> index 6def90e..c5c61c8 100644
>> --- a/net/compat.c
>> +++ b/net/compat.c
>> @@ -326,14 +326,6 @@ void scm_detach_fds_compat(struct msghdr *kmsg, struct scm_cookie *scm)
>>       __scm_destroy(scm);
>>  }
>>
>> -/*
>> - * A struct sock_filter is architecture independent.
>> - */
>> -struct compat_sock_fprog {
>> -     u16             len;
>> -     compat_uptr_t   filter;         /* struct sock_filter * */
>> -};
>> -
>>  static int do_set_attach_filter(struct socket *sock, int level, int optname,
>>                               char __user *optval, unsigned int optlen)
>>  {
>
> Acked-by: Eric Dumazet <eric.dumazet@gmail.com>

Added your Acked-by's to the tree at

  https://github.com/redpig/linux/tree/seccomp

Thanks!
will

[kernel-hardening] Re: [PATCH v15 02/13] net/compat.c,linux/filter.h: share compat_sock_fprog

[Will Drewry]

On Fri, Mar 16, 2012 at 1:16 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On Wed, 2012-03-14 at 22:11 -0500, Will Drewry wrote:
>> Any other users of bpf_*_filter that take a struct sock_fprog from
>> userspace will need to be able to also accept a compat_sock_fprog
>> if the arch supports compat calls.  This change let's the existing
>> compat_sock_fprog be shared.
>>
>> Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
>> Signed-off-by: Will Drewry <wad@chromium.org>
>>
>> v14: rebase/nochanges
>> v13: rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
>> v12: rebase on to linux-next
>> v11: introduction
>> ---
>>  include/linux/filter.h |   11 +++++++++++
>>  net/compat.c           |    8 --------
>>  2 files changed, 11 insertions(+), 8 deletions(-)
>>
>> diff --git a/include/linux/filter.h b/include/linux/filter.h
>> index aaa2e80..f2e5315 100644
>> --- a/include/linux/filter.h
>> +++ b/include/linux/filter.h
>> @@ -10,6 +10,7 @@
>>
>>  #ifdef __KERNEL__
>>  #include <linux/atomic.h>
>> +#include <linux/compat.h>
>>  #endif
>>
>>  /*
>> @@ -132,6 +133,16 @@ struct sock_fprog {      /* Required for SO_ATTACH_FILTER. */
>>
>>  #ifdef __KERNEL__
>>
>> +#ifdef CONFIG_COMPAT
>> +/*
>> + * A struct sock_filter is architecture independent.
>> + */
>> +struct compat_sock_fprog {
>> +     u16             len;
>> +     compat_uptr_t   filter;         /* struct sock_filter * */
>> +};
>> +#endif
>> +
>>  struct sk_buff;
>>  struct sock;
>>
>> diff --git a/net/compat.c b/net/compat.c
>> index 6def90e..c5c61c8 100644
>> --- a/net/compat.c
>> +++ b/net/compat.c
>> @@ -326,14 +326,6 @@ void scm_detach_fds_compat(struct msghdr *kmsg, struct scm_cookie *scm)
>>       __scm_destroy(scm);
>>  }
>>
>> -/*
>> - * A struct sock_filter is architecture independent.
>> - */
>> -struct compat_sock_fprog {
>> -     u16             len;
>> -     compat_uptr_t   filter;         /* struct sock_filter * */
>> -};
>> -
>>  static int do_set_attach_filter(struct socket *sock, int level, int optname,
>>                               char __user *optval, unsigned int optlen)
>>  {
>
> Acked-by: Eric Dumazet <eric.dumazet@gmail.com>

Added your Acked-by's to the tree at

  https://github.com/redpig/linux/tree/seccomp

Thanks!
will

Re: [PATCH v15 06/13] seccomp: add system call filtering using BPF

[Vladimir Murzin]

On Wed, Mar 14, 2012 at 10:11:58PM -0500, Will Drewry wrote:
> [This patch depends on luto@mit.edu's no_new_privs patch:
>    https://lkml.org/lkml/2012/1/30/264
>  The whole series including Andrew's patches can be found here:
>    https://github.com/redpig/linux/tree/seccomp
>  Complete diff here:
>    https://github.com/redpig/linux/compare/1dc65fed...seccomp
>  A GPG signed tag 'seccomp/v14/posted' will be pushed shortly.
> ]
> 
> This patch adds support for seccomp mode 2.  Mode 2 introduces the
> ability for unprivileged processes to install system call filtering
> policy expressed in terms of a Berkeley Packet Filter (BPF) program.
> This program will be evaluated in the kernel for each system call
> the task makes and computes a result based on data in the format
> of struct seccomp_data.
> 
> A filter program may be installed by calling:
>   struct sock_fprog fprog = { ... };
>   ...
>   prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &fprog);
> 
> The return value of the filter program determines if the system call is
> allowed to proceed or denied.  If the first filter program installed
> allows prctl(2) calls, then the above call may be made repeatedly
> by a task to further reduce its access to the kernel.  All attached
> programs must be evaluated before a system call will be allowed to
> proceed.
> 
> Filter programs will be inherited across fork/clone and execve.
> However, if the task attaching the filter is unprivileged
> (!CAP_SYS_ADMIN) the no_new_privs bit will be set on the task.  This
> ensures that unprivileged tasks cannot attach filters that affect
> privileged tasks (e.g., setuid binary).
> 
> There are a number of benefits to this approach. A few of which are
> as follows:
> - BPF has been exposed to userland for a long time
> - BPF optimization (and JIT'ing) are well understood
> - Userland already knows its ABI: system call numbers and desired
>   arguments
> - No time-of-check-time-of-use vulnerable data accesses are possible.
> - system call arguments are loaded on access only to minimize copying
>   required for system call policy decisions.
> 
> Mode 2 support is restricted to architectures that enable
> HAVE_ARCH_SECCOMP_FILTER.  In this patch, the primary dependency is on
> syscall_get_arguments().  The full desired scope of this feature will
> add a few minor additional requirements expressed later in this series.
> Based on discussion, SECCOMP_RET_ERRNO and SECCOMP_RET_TRACE seem to be
> the desired additional functionality.
> 
> No architectures are enabled in this patch.
> 
> v15: - add a 4 instr penalty when counting a path to account for seccomp_filter
>        size (indan@nul.nu)
>      - drop the max insns to 256KB (indan@nul.nu)
>      - return ENOMEM if the max insns limit has been hit (indan@nul.nu)
>      - move IP checks after args (indan@nul.nu)
>      - drop !user_filter check (indan@nul.nu)
>      - only allow explicit bpf codes (indan@nul.nu)
>      - exit_code -> exit_sig
> v14: - put/get_seccomp_filter takes struct task_struct
>        (indan@nul.nu,keescook@chromium.org)
>      - adds seccomp_chk_filter and drops general bpf_run/chk_filter user
>      - add seccomp_bpf_load for use by net/core/filter.c
>      - lower max per-process/per-hierarchy: 1MB
>      - moved nnp/capability check prior to allocation
>        (all of the above: indan@nul.nu)
> v13: - rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
> v12: - added a maximum instruction count per path (indan@nul.nu,oleg@redhat.com)
>      - removed copy_seccomp (keescook@chromium.org,indan@nul.nu)
>      - reworded the prctl_set_seccomp comment (indan@nul.nu)
> v11: - reorder struct seccomp_data to allow future args expansion (hpa@zytor.com)
>      - style clean up, @compat dropped, compat_sock_fprog32 (indan@nul.nu)
>      - do_exit(SIGSYS) (keescook@chromium.org, luto@mit.edu)
>      - pare down Kconfig doc reference.
>      - extra comment clean up
> v10: - seccomp_data has changed again to be more aesthetically pleasing
>        (hpa@zytor.com)
>      - calling convention is noted in a new u32 field using syscall_get_arch.
>        This allows for cross-calling convention tasks to use seccomp filters.
>        (hpa@zytor.com)
>      - lots of clean up (thanks, Indan!)
>  v9: - n/a
>  v8: - use bpf_chk_filter, bpf_run_filter. update load_fns
>      - Lots of fixes courtesy of indan@nul.nu:
>      -- fix up load behavior, compat fixups, and merge alloc code,
>      -- renamed pc and dropped __packed, use bool compat.
>      -- Added a hidden CONFIG_SECCOMP_FILTER to synthesize non-arch
>         dependencies
>  v7:  (massive overhaul thanks to Indan, others)
>      - added CONFIG_HAVE_ARCH_SECCOMP_FILTER
>      - merged into seccomp.c
>      - minimal seccomp_filter.h
>      - no config option (part of seccomp)
>      - no new prctl
>      - doesn't break seccomp on systems without asm/syscall.h
>        (works but arg access always fails)
>      - dropped seccomp_init_task, extra free functions, ...
>      - dropped the no-asm/syscall.h code paths
>      - merges with network sk_run_filter and sk_chk_filter
>  v6: - fix memory leak on attach compat check failure
>      - require no_new_privs || CAP_SYS_ADMIN prior to filter
>        installation. (luto@mit.edu)
>      - s/seccomp_struct_/seccomp_/ for macros/functions (amwang@redhat.com)
>      - cleaned up Kconfig (amwang@redhat.com)
>      - on block, note if the call was compat (so the # means something)
>  v5: - uses syscall_get_arguments
>        (indan@nul.nu,oleg@redhat.com, mcgrathr@chromium.org)
>       - uses union-based arg storage with hi/lo struct to
>         handle endianness.  Compromises between the two alternate
>         proposals to minimize extra arg shuffling and account for
>         endianness assuming userspace uses offsetof().
>         (mcgrathr@chromium.org, indan@nul.nu)
>       - update Kconfig description
>       - add include/seccomp_filter.h and add its installation
>       - (naive) on-demand syscall argument loading
>       - drop seccomp_t (eparis@redhat.com)
>  v4:  - adjusted prctl to make room for PR_[SG]ET_NO_NEW_PRIVS
>       - now uses current->no_new_privs
>         (luto@mit.edu,torvalds@linux-foundation.com)
>       - assign names to seccomp modes (rdunlap@xenotime.net)
>       - fix style issues (rdunlap@xenotime.net)
>       - reworded Kconfig entry (rdunlap@xenotime.net)
>  v3:  - macros to inline (oleg@redhat.com)
>       - init_task behavior fixed (oleg@redhat.com)
>       - drop creator entry and extra NULL check (oleg@redhat.com)
>       - alloc returns -EINVAL on bad sizing (serge.hallyn@canonical.com)
>       - adds tentative use of "always_unprivileged" as per
>         torvalds@linux-foundation.org and luto@mit.edu
>  v2:  - (patch 2 only)
> 
> Reviewed-by: Indan Zupancic <indan@nul.nu>
> Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
> 
> Signed-off-by: Will Drewry <wad@chromium.org>
> ---
>  arch/Kconfig            |   17 ++
>  include/linux/Kbuild    |    1 +
>  include/linux/seccomp.h |   76 +++++++++-
>  kernel/fork.c           |    3 +
>  kernel/seccomp.c        |  391 ++++++++++++++++++++++++++++++++++++++++++++---
>  kernel/sys.c            |    2 +-
>  6 files changed, 467 insertions(+), 23 deletions(-)
> 
> diff --git a/arch/Kconfig b/arch/Kconfig
> index 4f55c73..7c6bd48 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -199,4 +199,21 @@ config HAVE_CMPXCHG_LOCAL
>  config HAVE_CMPXCHG_DOUBLE
>  	bool
>  
> +config HAVE_ARCH_SECCOMP_FILTER
> +	bool
> +	help
> +	  This symbol should be selected by an architecure if it provides
> +	  asm/syscall.h, specifically syscall_get_arguments() and
> +	  syscall_get_arch().
> +
> +config SECCOMP_FILTER
> +	def_bool y
> +	depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
> +	help
> +	  Enable tasks to build secure computing environments defined
> +	  in terms of Berkeley Packet Filter programs which implement
> +	  task-defined system call filtering polices.
> +
> +	  See Documentation/prctl/seccomp_filter.txt for details.
> +
>  source "kernel/gcov/Kconfig"
> diff --git a/include/linux/Kbuild b/include/linux/Kbuild
> index c94e717..d41ba12 100644
> --- a/include/linux/Kbuild
> +++ b/include/linux/Kbuild
> @@ -330,6 +330,7 @@ header-y += scc.h
>  header-y += sched.h
>  header-y += screen_info.h
>  header-y += sdla.h
> +header-y += seccomp.h
>  header-y += securebits.h
>  header-y += selinux_netlink.h
>  header-y += sem.h
> diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
> index d61f27f..ce980a8 100644
> --- a/include/linux/seccomp.h
> +++ b/include/linux/seccomp.h
> @@ -1,14 +1,67 @@
>  #ifndef _LINUX_SECCOMP_H
>  #define _LINUX_SECCOMP_H
>  
> +#include <linux/compiler.h>
> +#include <linux/types.h>
> +
> +
> +/* Valid values for seccomp.mode and prctl(PR_SET_SECCOMP, <mode>) */
> +#define SECCOMP_MODE_DISABLED	0 /* seccomp is not in use. */
> +#define SECCOMP_MODE_STRICT	1 /* uses hard-coded filter. */
> +#define SECCOMP_MODE_FILTER	2 /* uses user-supplied filter. */
> +
> +/*
> + * All BPF programs must return a 32-bit value.
> + * The bottom 16-bits are reserved for future use.
> + * The upper 16-bits are ordered from least permissive values to most.
> + *
> + * The ordering ensures that a min_t() over composed return values always
> + * selects the least permissive choice.
> + */
> +#define SECCOMP_RET_KILL	0x00000000U /* kill the task immediately */
> +#define SECCOMP_RET_ALLOW	0x7fff0000U /* allow */
> +
> +/* Masks for the return value sections. */
> +#define SECCOMP_RET_ACTION	0xffff0000U
> +#define SECCOMP_RET_DATA	0x0000ffffU
> +
> +/**
> + * struct seccomp_data - the format the BPF program executes over.
> + * @nr: the system call number
> + * @arch: indicates system call convention as an AUDIT_ARCH_* value
> + *        as defined in <linux/audit.h>.
> + * @instruction_pointer: at the time of the system call.
> + * @args: up to 6 system call arguments always stored as 64-bit values
> + *        regardless of the architecture.
> + */
> +struct seccomp_data {
> +	int nr;
> +	__u32 arch;
> +	__u64 instruction_pointer;
> +	__u64 args[6];
> +};
>  
> +#ifdef __KERNEL__
>  #ifdef CONFIG_SECCOMP
>  
>  #include <linux/thread_info.h>
>  #include <asm/seccomp.h>
>  
> +struct seccomp_filter;
> +/**
> + * struct seccomp - the state of a seccomp'ed process
> + *
> + * @mode:  indicates one of the valid values above for controlled
> + *         system calls available to a process.
> + * @filter: The metadata and ruleset for determining what system calls
> + *          are allowed for a task.
> + *
> + *          @filter must only be accessed from the context of current as there
> + *          is no locking.
> + */
>  struct seccomp {
>  	int mode;
> +	struct seccomp_filter *filter;
>  };
>  
>  extern void __secure_computing(int);
> @@ -19,7 +72,7 @@ static inline void secure_computing(int this_syscall)
>  }
>  
>  extern long prctl_get_seccomp(void);
> -extern long prctl_set_seccomp(unsigned long);
> +extern long prctl_set_seccomp(unsigned long, char __user *);
>  
>  static inline int seccomp_mode(struct seccomp *s)
>  {
> @@ -31,15 +84,16 @@ static inline int seccomp_mode(struct seccomp *s)
>  #include <linux/errno.h>
>  
>  struct seccomp { };
> +struct seccomp_filter { };
>  
> -#define secure_computing(x) do { } while (0)
> +#define secure_computing(x) 0
>  
>  static inline long prctl_get_seccomp(void)
>  {
>  	return -EINVAL;
>  }
>  
> -static inline long prctl_set_seccomp(unsigned long arg2)
> +static inline long prctl_set_seccomp(unsigned long arg2, char __user *arg3)
>  {
>  	return -EINVAL;
>  }
> @@ -48,7 +102,21 @@ static inline int seccomp_mode(struct seccomp *s)
>  {
>  	return 0;
>  }
> -
>  #endif /* CONFIG_SECCOMP */
>  
> +#ifdef CONFIG_SECCOMP_FILTER
> +extern void put_seccomp_filter(struct task_struct *tsk);
> +extern void get_seccomp_filter(struct task_struct *tsk);
> +extern u32 seccomp_bpf_load(int off);
> +#else  /* CONFIG_SECCOMP_FILTER */
> +static inline void put_seccomp_filter(struct task_struct *tsk)
> +{
> +	return;
> +}
> +static inline void get_seccomp_filter(struct task_struct *tsk)
> +{
> +	return;
> +}
> +#endif /* CONFIG_SECCOMP_FILTER */
> +#endif /* __KERNEL__ */
>  #endif /* _LINUX_SECCOMP_H */
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 26a7a67..4f7a186 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -34,6 +34,7 @@
>  #include <linux/cgroup.h>
>  #include <linux/security.h>
>  #include <linux/hugetlb.h>
> +#include <linux/seccomp.h>
>  #include <linux/swap.h>
>  #include <linux/syscalls.h>
>  #include <linux/jiffies.h>
> @@ -170,6 +171,7 @@ void free_task(struct task_struct *tsk)
>  	free_thread_info(tsk->stack);
>  	rt_mutex_debug_task_free(tsk);
>  	ftrace_graph_exit_task(tsk);
> +	put_seccomp_filter(tsk);
>  	free_task_struct(tsk);
>  }
>  EXPORT_SYMBOL(free_task);
> @@ -1143,6 +1145,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
>  		goto fork_out;
>  
>  	ftrace_graph_init_task(p);
> +	get_seccomp_filter(p);
>  
>  	rt_mutex_init_task(p);
>  
> diff --git a/kernel/seccomp.c b/kernel/seccomp.c
> index e8d76c5..9e50174 100644
> --- a/kernel/seccomp.c
> +++ b/kernel/seccomp.c
> @@ -3,16 +3,338 @@
>   *
>   * Copyright 2004-2005  Andrea Arcangeli <andrea@cpushare.com>
>   *
> - * This defines a simple but solid secure-computing mode.
> + * Copyright (C) 2012 Google, Inc.
> + * Will Drewry <wad@chromium.org>
> + *
> + * This defines a simple but solid secure-computing facility.
> + *
> + * Mode 1 uses a fixed list of allowed system calls.
> + * Mode 2 allows user-defined system call filters in the form
> + *        of Berkeley Packet Filters/Linux Socket Filters.
>   */
>  
> +#include <linux/atomic.h>
>  #include <linux/audit.h>
> -#include <linux/seccomp.h>
> -#include <linux/sched.h>
>  #include <linux/compat.h>
> +#include <linux/filter.h>
> +#include <linux/sched.h>
> +#include <linux/seccomp.h>
> +#include <linux/security.h>
> +#include <linux/slab.h>
> +#include <linux/uaccess.h>
> +
> +#include <linux/tracehook.h>
> +#include <asm/syscall.h>
>  
>  /* #define SECCOMP_DEBUG 1 */
> -#define NR_SECCOMP_MODES 1
> +
> +#ifdef CONFIG_SECCOMP_FILTER
> +/**
> + * struct seccomp_filter - container for seccomp BPF programs
> + *
> + * @usage: reference count to manage the object liftime.
> + *         get/put helpers should be used when accessing an instance
> + *         outside of a lifetime-guarded section.  In general, this
> + *         is only needed for handling filters shared across tasks.
> + * @prev: points to a previously installed, or inherited, filter
> + * @len: the number of instructions in the program
> + * @insns: the BPF program instructions to evaluate
> + *
> + * seccomp_filter objects are organized in a tree linked via the @prev
> + * pointer.  For any task, it appears to be a singly-linked list starting
> + * with current->seccomp.filter, the most recently attached or inherited filter.
> + * However, multiple filters may share a @prev node, by way of fork(), which
> + * results in a unidirectional tree existing in memory.  This is similar to
> + * how namespaces work.
> + *
> + * seccomp_filter objects should never be modified after being attached
> + * to a task_struct (other than @usage).
> + */
> +struct seccomp_filter {
> +	atomic_t usage;
> +	struct seccomp_filter *prev;
> +	unsigned short len;  /* Instruction count */
> +	struct sock_filter insns[];
> +};
> +
> +/* Limit any path through the tree to 256KB worth of instructions. */
> +#define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter))
> +
> +static void seccomp_filter_log_failure(int syscall)
> +{
> +	int compat = 0;
> +#ifdef CONFIG_COMPAT
> +	compat = is_compat_task();
> +#endif
> +	pr_info("%s[%d]: %ssystem call %d blocked at 0x%lx\n",
> +		current->comm, task_pid_nr(current),
> +		(compat ? "compat " : ""),
> +		syscall, KSTK_EIP(current));
> +}
> +

Do we really need to surround is_compat_task() with CNFIG_COMPAT?
It seems that this case has already handled in include/linux/compat.h [1]

> +/**
> + * get_u32 - returns a u32 offset into data
> + * @data: a unsigned 64 bit value
> + * @index: 0 or 1 to return the first or second 32-bits
> + *
> + * This inline exists to hide the length of unsigned long.
> + * If a 32-bit unsigned long is passed in, it will be extended
> + * and the top 32-bits will be 0. If it is a 64-bit unsigned
> + * long, then whatever data is resident will be properly returned.
> + */
> +static inline u32 get_u32(u64 data, int index)
> +{
> +	return ((u32 *)&data)[index];
> +}
> +
> +/* Helper for bpf_load below. */
> +#define BPF_DATA(_name) offsetof(struct seccomp_data, _name)
> +/**
> + * bpf_load: checks and returns a pointer to the requested offset
> + * @off: offset into struct seccomp_data to load from
> + *
> + * Returns the requested 32-bits of data.
> + * seccomp_chk_filter() should assure that @off is 32-bit aligned
> + * and not out of bounds.  Failure to do so is a BUG.
> + */
> +u32 seccomp_bpf_load(int off)
> +{
> +	struct pt_regs *regs = task_pt_regs(current);
> +	if (off == BPF_DATA(nr))
> +		return syscall_get_nr(current, regs);
> +	if (off == BPF_DATA(arch))
> +		return syscall_get_arch(current, regs);
> +	if (off >= BPF_DATA(args[0]) && off < BPF_DATA(args[6])) {
> +		unsigned long value;
> +		int arg = (off - BPF_DATA(args[0])) / sizeof(u64);
> +		int index = !!(off % sizeof(u64));
> +		syscall_get_arguments(current, regs, arg, 1, &value);
> +		return get_u32(value, index);
> +	}
> +	if (off == BPF_DATA(instruction_pointer))
> +		return get_u32(KSTK_EIP(current), 0);
> +	if (off == BPF_DATA(instruction_pointer) + sizeof(u32))
> +		return get_u32(KSTK_EIP(current), 1);
> +	/* seccomp_chk_filter should make this impossible. */
> +	BUG();
> +}
> +
> +/**
> + *	seccomp_chk_filter - verify seccomp filter code
> + *	@filter: filter to verify
> + *	@flen: length of filter
> + *
> + * Takes a previously checked filter (by sk_chk_filter) and
> + * redirects all filter code that loads struct sk_buff data
> + * and related data through seccomp_bpf_load.  It also
> + * enforces length and alignment checking of those loads.
> + *
> + * Returns 0 if the rule set is legal or -EINVAL if not.
> + */
> +static int seccomp_chk_filter(struct sock_filter *filter, unsigned int flen)
> +{
> +	int pc;
> +	for (pc = 0; pc < flen; pc++) {
> +		struct sock_filter *ftest = &filter[pc];
> +		u16 code = ftest->code;
> +		u32 k = ftest->k;
> +		switch (code) {
> +		case BPF_S_LD_W_ABS:
> +			ftest->code = BPF_S_ANC_SECCOMP_LD_W;
> +			/* 32-bit aligned and not out of bounds. */
> +			if (k >= sizeof(struct seccomp_data) || k & 3)
> +				return -EINVAL;
> +			continue;
> +		case BPF_S_LD_W_LEN:
> +			ftest->code = BPF_S_LD_IMM;
> +			ftest->k = sizeof(struct seccomp_data);
> +			continue;
> +		case BPF_S_LDX_W_LEN:
> +			ftest->code = BPF_S_LDX_IMM;
> +			ftest->k = sizeof(struct seccomp_data);
> +			continue;
> +		/* Explicitly include allowed calls. */
> +		case BPF_S_RET_K:
> +		case BPF_S_RET_A:
> +		case BPF_S_ALU_ADD_K:
> +		case BPF_S_ALU_ADD_X:
> +		case BPF_S_ALU_SUB_K:
> +		case BPF_S_ALU_SUB_X:
> +		case BPF_S_ALU_MUL_K:
> +		case BPF_S_ALU_MUL_X:
> +		case BPF_S_ALU_DIV_X:
> +		case BPF_S_ALU_AND_K:
> +		case BPF_S_ALU_AND_X:
> +		case BPF_S_ALU_OR_K:
> +		case BPF_S_ALU_OR_X:
> +		case BPF_S_ALU_LSH_K:
> +		case BPF_S_ALU_LSH_X:
> +		case BPF_S_ALU_RSH_K:
> +		case BPF_S_ALU_RSH_X:
> +		case BPF_S_ALU_NEG:
> +		case BPF_S_LD_IMM:
> +		case BPF_S_LDX_IMM:
> +		case BPF_S_MISC_TAX:
> +		case BPF_S_MISC_TXA:
> +		case BPF_S_ALU_DIV_K:
> +		case BPF_S_LD_MEM:
> +		case BPF_S_LDX_MEM:
> +		case BPF_S_ST:
> +		case BPF_S_STX:
> +		case BPF_S_JMP_JA:
> +		case BPF_S_JMP_JEQ_K:
> +		case BPF_S_JMP_JEQ_X:
> +		case BPF_S_JMP_JGE_K:
> +		case BPF_S_JMP_JGE_X:
> +		case BPF_S_JMP_JGT_K:
> +		case BPF_S_JMP_JGT_X:
> +		case BPF_S_JMP_JSET_K:
> +		case BPF_S_JMP_JSET_X:
> +			continue;
> +		default:
> +			return -EINVAL;
> +		}
> +	}
> +	return 0;
> +}
> +
> +/**
> + * seccomp_run_filters - evaluates all seccomp filters against @syscall
> + * @syscall: number of the current system call
> + *
> + * Returns valid seccomp BPF response codes.
> + */
> +static u32 seccomp_run_filters(int syscall)
> +{
> +	struct seccomp_filter *f;
> +	u32 ret = SECCOMP_RET_KILL;
> +	/*
> +	 * All filters are evaluated in order of youngest to oldest. The lowest
> +	 * BPF return value always takes priority.
> +	 */
> +	for (f = current->seccomp.filter; f; f = f->prev) {
> +		ret = sk_run_filter(NULL, f->insns);
> +		if (ret != SECCOMP_RET_ALLOW)
> +			break;
> +	}
> +	return ret;
> +}
> +
> +/**
> + * seccomp_attach_filter: Attaches a seccomp filter to current.
> + * @fprog: BPF program to install
> + *
> + * Returns 0 on success or an errno on failure.
> + */
> +static long seccomp_attach_filter(struct sock_fprog *fprog)
> +{
> +	struct seccomp_filter *filter;
> +	unsigned long fp_size = fprog->len * sizeof(struct sock_filter);
> +	unsigned long total_insns = fprog->len;
> +	long ret;
> +
> +	if (fprog->len == 0 || fprog->len > BPF_MAXINSNS)
> +		return -EINVAL;
> +
> +	for (filter = current->seccomp.filter; filter; filter = filter->prev)
> +		total_insns += filter->len + 4;  /* include a 4 instr penalty */
> +	if (total_insns > MAX_INSNS_PER_PATH)
> +		return -ENOMEM;
> +
> +	/*
> +	 * Installing a seccomp filter requires that the task have
> +	 * CAP_SYS_ADMIN in its namespace or be running with no_new_privs.
> +	 * This avoids scenarios where unprivileged tasks can affect the
> +	 * behavior of privileged children.
> +	 */
> +	if (!current->no_new_privs &&
> +	    security_capable_noaudit(current_cred(), current_user_ns(),
> +				     CAP_SYS_ADMIN) != 0)
> +		return -EACCES;
> +
> +	/* Allocate a new seccomp_filter */
> +	filter = kzalloc(sizeof(struct seccomp_filter) + fp_size, GFP_KERNEL);
> +	if (!filter)
> +		return -ENOMEM;
> +	atomic_set(&filter->usage, 1);
> +	filter->len = fprog->len;
> +
> +	/* Copy the instructions from fprog. */
> +	ret = -EFAULT;
> +	if (copy_from_user(filter->insns, fprog->filter, fp_size))
> +		goto fail;
> +
> +	/* Check and rewrite the fprog via the skb checker */
> +	ret = sk_chk_filter(filter->insns, filter->len);
> +	if (ret)
> +		goto fail;
> +
> +	/* Check and rewrite the fprog for seccomp use */
> +	ret = seccomp_chk_filter(filter->insns, filter->len);
> +	if (ret)
> +		goto fail;
> +
> +	/*
> +	 * If there is an existing filter, make it the prev and don't drop its
> +	 * task reference.
> +	 */
> +	filter->prev = current->seccomp.filter;
> +	current->seccomp.filter = filter;
> +	return 0;
> +fail:
> +	kfree(filter);
> +	return ret;
> +}
> +
> +/**
> + * seccomp_attach_user_filter - attaches a user-supplied sock_fprog
> + * @user_filter: pointer to the user data containing a sock_fprog.
> + *
> + * Returns 0 on success and non-zero otherwise.
> + */
> +long seccomp_attach_user_filter(char __user *user_filter)
> +{
> +	struct sock_fprog fprog;
> +	long ret = -EFAULT;
> +
> +#ifdef CONFIG_COMPAT
> +	if (is_compat_task()) {
> +		struct compat_sock_fprog fprog32;
> +		if (copy_from_user(&fprog32, user_filter, sizeof(fprog32)))
> +			goto out;
> +		fprog.len = fprog32.len;
> +		fprog.filter = compat_ptr(fprog32.filter);
> +	} else /* falls through to the if below. */
> +#endif
> +	if (copy_from_user(&fprog, user_filter, sizeof(fprog)))
> +		goto out;
> +	ret = seccomp_attach_filter(&fprog);
> +out:
> +	return ret;
> +}

The same note about CONFIG_COMPAT as above.

> +
> +/* get_seccomp_filter - increments the reference count of the filter on @tsk */
> +void get_seccomp_filter(struct task_struct *tsk)
> +{
> +	struct seccomp_filter *orig = tsk->seccomp.filter;
> +	if (!orig)
> +		return;
> +	/* Reference count is bounded by the number of total processes. */
> +	atomic_inc(&orig->usage);
> +}
> +
> +/* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */
> +void put_seccomp_filter(struct task_struct *tsk)
> +{
> +	struct seccomp_filter *orig = tsk->seccomp.filter;
> +	/* Clean up single-reference branches iteratively. */
> +	while (orig && atomic_dec_and_test(&orig->usage)) {
> +		struct seccomp_filter *freeme = orig;
> +		orig = orig->prev;
> +		kfree(freeme);
> +	}
> +}
> +#endif	/* CONFIG_SECCOMP_FILTER */
>  
>  /*
>   * Secure computing mode 1 allows only read/write/exit/sigreturn.
> @@ -34,10 +356,11 @@ static int mode1_syscalls_32[] = {
>  void __secure_computing(int this_syscall)
>  {
>  	int mode = current->seccomp.mode;
> -	int * syscall;
> +	int exit_sig = 0;
> +	int *syscall;
>  
>  	switch (mode) {
> -	case 1:
> +	case SECCOMP_MODE_STRICT:
>  		syscall = mode1_syscalls;
>  #ifdef CONFIG_COMPAT
>  		if (is_compat_task())
> @@ -47,7 +370,16 @@ void __secure_computing(int this_syscall)
>  			if (*syscall == this_syscall)
>  				return;
>  		} while (*++syscall);
> +		exit_sig = SIGKILL;
> +		break;
> +#ifdef CONFIG_SECCOMP_FILTER
> +	case SECCOMP_MODE_FILTER:
> +		if (seccomp_run_filters(this_syscall) == SECCOMP_RET_ALLOW)
> +			return;
> +		seccomp_filter_log_failure(this_syscall);
> +		exit_sig = SIGSYS;
>  		break;
> +#endif
>  	default:
>  		BUG();
>  	}
> @@ -56,7 +388,7 @@ void __secure_computing(int this_syscall)
>  	dump_stack();
>  #endif
>  	audit_seccomp(this_syscall);
> -	do_exit(SIGKILL);
> +	do_exit(exit_sig);
>  }
>  
>  long prctl_get_seccomp(void)
> @@ -64,25 +396,48 @@ long prctl_get_seccomp(void)
>  	return current->seccomp.mode;
>  }
>  
> -long prctl_set_seccomp(unsigned long seccomp_mode)
> +/**
> + * prctl_set_seccomp: configures current->seccomp.mode
> + * @seccomp_mode: requested mode to use
> + * @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER
> + *
> + * This function may be called repeatedly with a @seccomp_mode of
> + * SECCOMP_MODE_FILTER to install additional filters.  Every filter
> + * successfully installed will be evaluated (in reverse order) for each system
> + * call the task makes.
> + *
> + * Once current->seccomp.mode is non-zero, it may not be changed.
> + *
> + * Returns 0 on success or -EINVAL on failure.
> + */
> +long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter)
>  {
> -	long ret;
> +	long ret = -EINVAL;
>  
> -	/* can set it only once to be even more secure */
> -	ret = -EPERM;
> -	if (unlikely(current->seccomp.mode))
> +	if (current->seccomp.mode &&
> +	    current->seccomp.mode != seccomp_mode)
>  		goto out;
>  
> -	ret = -EINVAL;
> -	if (seccomp_mode && seccomp_mode <= NR_SECCOMP_MODES) {
> -		current->seccomp.mode = seccomp_mode;
> -		set_thread_flag(TIF_SECCOMP);
> +	switch (seccomp_mode) {
> +	case SECCOMP_MODE_STRICT:
> +		ret = 0;
>  #ifdef TIF_NOTSC
>  		disable_TSC();
>  #endif
> -		ret = 0;
> +		break;
> +#ifdef CONFIG_SECCOMP_FILTER
> +	case SECCOMP_MODE_FILTER:
> +		ret = seccomp_attach_user_filter(filter);
> +		if (ret)
> +			goto out;
> +		break;
> +#endif
> +	default:
> +		goto out;
>  	}
>  
> - out:
> +	current->seccomp.mode = seccomp_mode;
> +	set_thread_flag(TIF_SECCOMP);
> +out:
>  	return ret;
>  }
> diff --git a/kernel/sys.c b/kernel/sys.c
> index 12e862a..038e6b7 100644
> --- a/kernel/sys.c
> +++ b/kernel/sys.c
> @@ -1899,7 +1899,7 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
>  			error = prctl_get_seccomp();
>  			break;
>  		case PR_SET_SECCOMP:
> -			error = prctl_set_seccomp(arg2);
> +			error = prctl_set_seccomp(arg2, (char __user *)arg3);
>  			break;
>  		case PR_GET_TSC:
>  			error = GET_TSC_CTL(arg2);
> -- 
> 1.7.5.4
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-arch" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

[1] http://lxr.linux.no/#linux+v3.3/include/linux/compat.h#L566

Best wishes
Vladimir Murzin

[kernel-hardening] Re: [PATCH v15 06/13] seccomp: add system call filtering using BPF

[Vladimir Murzin]

On Wed, Mar 14, 2012 at 10:11:58PM -0500, Will Drewry wrote:
> [This patch depends on luto@mit.edu's no_new_privs patch:
>    https://lkml.org/lkml/2012/1/30/264
>  The whole series including Andrew's patches can be found here:
>    https://github.com/redpig/linux/tree/seccomp
>  Complete diff here:
>    https://github.com/redpig/linux/compare/1dc65fed...seccomp
>  A GPG signed tag 'seccomp/v14/posted' will be pushed shortly.
> ]
> 
> This patch adds support for seccomp mode 2.  Mode 2 introduces the
> ability for unprivileged processes to install system call filtering
> policy expressed in terms of a Berkeley Packet Filter (BPF) program.
> This program will be evaluated in the kernel for each system call
> the task makes and computes a result based on data in the format
> of struct seccomp_data.
> 
> A filter program may be installed by calling:
>   struct sock_fprog fprog = { ... };
>   ...
>   prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &fprog);
> 
> The return value of the filter program determines if the system call is
> allowed to proceed or denied.  If the first filter program installed
> allows prctl(2) calls, then the above call may be made repeatedly
> by a task to further reduce its access to the kernel.  All attached
> programs must be evaluated before a system call will be allowed to
> proceed.
> 
> Filter programs will be inherited across fork/clone and execve.
> However, if the task attaching the filter is unprivileged
> (!CAP_SYS_ADMIN) the no_new_privs bit will be set on the task.  This
> ensures that unprivileged tasks cannot attach filters that affect
> privileged tasks (e.g., setuid binary).
> 
> There are a number of benefits to this approach. A few of which are
> as follows:
> - BPF has been exposed to userland for a long time
> - BPF optimization (and JIT'ing) are well understood
> - Userland already knows its ABI: system call numbers and desired
>   arguments
> - No time-of-check-time-of-use vulnerable data accesses are possible.
> - system call arguments are loaded on access only to minimize copying
>   required for system call policy decisions.
> 
> Mode 2 support is restricted to architectures that enable
> HAVE_ARCH_SECCOMP_FILTER.  In this patch, the primary dependency is on
> syscall_get_arguments().  The full desired scope of this feature will
> add a few minor additional requirements expressed later in this series.
> Based on discussion, SECCOMP_RET_ERRNO and SECCOMP_RET_TRACE seem to be
> the desired additional functionality.
> 
> No architectures are enabled in this patch.
> 
> v15: - add a 4 instr penalty when counting a path to account for seccomp_filter
>        size (indan@nul.nu)
>      - drop the max insns to 256KB (indan@nul.nu)
>      - return ENOMEM if the max insns limit has been hit (indan@nul.nu)
>      - move IP checks after args (indan@nul.nu)
>      - drop !user_filter check (indan@nul.nu)
>      - only allow explicit bpf codes (indan@nul.nu)
>      - exit_code -> exit_sig
> v14: - put/get_seccomp_filter takes struct task_struct
>        (indan@nul.nu,keescook@chromium.org)
>      - adds seccomp_chk_filter and drops general bpf_run/chk_filter user
>      - add seccomp_bpf_load for use by net/core/filter.c
>      - lower max per-process/per-hierarchy: 1MB
>      - moved nnp/capability check prior to allocation
>        (all of the above: indan@nul.nu)
> v13: - rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc
> v12: - added a maximum instruction count per path (indan@nul.nu,oleg@redhat.com)
>      - removed copy_seccomp (keescook@chromium.org,indan@nul.nu)
>      - reworded the prctl_set_seccomp comment (indan@nul.nu)
> v11: - reorder struct seccomp_data to allow future args expansion (hpa@zytor.com)
>      - style clean up, @compat dropped, compat_sock_fprog32 (indan@nul.nu)
>      - do_exit(SIGSYS) (keescook@chromium.org, luto@mit.edu)
>      - pare down Kconfig doc reference.
>      - extra comment clean up
> v10: - seccomp_data has changed again to be more aesthetically pleasing
>        (hpa@zytor.com)
>      - calling convention is noted in a new u32 field using syscall_get_arch.
>        This allows for cross-calling convention tasks to use seccomp filters.
>        (hpa@zytor.com)
>      - lots of clean up (thanks, Indan!)
>  v9: - n/a
>  v8: - use bpf_chk_filter, bpf_run_filter. update load_fns
>      - Lots of fixes courtesy of indan@nul.nu:
>      -- fix up load behavior, compat fixups, and merge alloc code,
>      -- renamed pc and dropped __packed, use bool compat.
>      -- Added a hidden CONFIG_SECCOMP_FILTER to synthesize non-arch
>         dependencies
>  v7:  (massive overhaul thanks to Indan, others)
>      - added CONFIG_HAVE_ARCH_SECCOMP_FILTER
>      - merged into seccomp.c
>      - minimal seccomp_filter.h
>      - no config option (part of seccomp)
>      - no new prctl
>      - doesn't break seccomp on systems without asm/syscall.h
>        (works but arg access always fails)
>      - dropped seccomp_init_task, extra free functions, ...
>      - dropped the no-asm/syscall.h code paths
>      - merges with network sk_run_filter and sk_chk_filter
>  v6: - fix memory leak on attach compat check failure
>      - require no_new_privs || CAP_SYS_ADMIN prior to filter
>        installation. (luto@mit.edu)
>      - s/seccomp_struct_/seccomp_/ for macros/functions (amwang@redhat.com)
>      - cleaned up Kconfig (amwang@redhat.com)
>      - on block, note if the call was compat (so the # means something)
>  v5: - uses syscall_get_arguments
>        (indan@nul.nu,oleg@redhat.com, mcgrathr@chromium.org)
>       - uses union-based arg storage with hi/lo struct to
>         handle endianness.  Compromises between the two alternate
>         proposals to minimize extra arg shuffling and account for
>         endianness assuming userspace uses offsetof().
>         (mcgrathr@chromium.org, indan@nul.nu)
>       - update Kconfig description
>       - add include/seccomp_filter.h and add its installation
>       - (naive) on-demand syscall argument loading
>       - drop seccomp_t (eparis@redhat.com)
>  v4:  - adjusted prctl to make room for PR_[SG]ET_NO_NEW_PRIVS
>       - now uses current->no_new_privs
>         (luto@mit.edu,torvalds@linux-foundation.com)
>       - assign names to seccomp modes (rdunlap@xenotime.net)
>       - fix style issues (rdunlap@xenotime.net)
>       - reworded Kconfig entry (rdunlap@xenotime.net)
>  v3:  - macros to inline (oleg@redhat.com)
>       - init_task behavior fixed (oleg@redhat.com)
>       - drop creator entry and extra NULL check (oleg@redhat.com)
>       - alloc returns -EINVAL on bad sizing (serge.hallyn@canonical.com)
>       - adds tentative use of "always_unprivileged" as per
>         torvalds@linux-foundation.org and luto@mit.edu
>  v2:  - (patch 2 only)
> 
> Reviewed-by: Indan Zupancic <indan@nul.nu>
> Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
> 
> Signed-off-by: Will Drewry <wad@chromium.org>
> ---
>  arch/Kconfig            |   17 ++
>  include/linux/Kbuild    |    1 +
>  include/linux/seccomp.h |   76 +++++++++-
>  kernel/fork.c           |    3 +
>  kernel/seccomp.c        |  391 ++++++++++++++++++++++++++++++++++++++++++++---
>  kernel/sys.c            |    2 +-
>  6 files changed, 467 insertions(+), 23 deletions(-)
> 
> diff --git a/arch/Kconfig b/arch/Kconfig
> index 4f55c73..7c6bd48 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -199,4 +199,21 @@ config HAVE_CMPXCHG_LOCAL
>  config HAVE_CMPXCHG_DOUBLE
>  	bool
>  
> +config HAVE_ARCH_SECCOMP_FILTER
> +	bool
> +	help
> +	  This symbol should be selected by an architecure if it provides
> +	  asm/syscall.h, specifically syscall_get_arguments() and
> +	  syscall_get_arch().
> +
> +config SECCOMP_FILTER
> +	def_bool y
> +	depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
> +	help
> +	  Enable tasks to build secure computing environments defined
> +	  in terms of Berkeley Packet Filter programs which implement
> +	  task-defined system call filtering polices.
> +
> +	  See Documentation/prctl/seccomp_filter.txt for details.
> +
>  source "kernel/gcov/Kconfig"
> diff --git a/include/linux/Kbuild b/include/linux/Kbuild
> index c94e717..d41ba12 100644
> --- a/include/linux/Kbuild
> +++ b/include/linux/Kbuild
> @@ -330,6 +330,7 @@ header-y += scc.h
>  header-y += sched.h
>  header-y += screen_info.h
>  header-y += sdla.h
> +header-y += seccomp.h
>  header-y += securebits.h
>  header-y += selinux_netlink.h
>  header-y += sem.h
> diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
> index d61f27f..ce980a8 100644
> --- a/include/linux/seccomp.h
> +++ b/include/linux/seccomp.h
> @@ -1,14 +1,67 @@
>  #ifndef _LINUX_SECCOMP_H
>  #define _LINUX_SECCOMP_H
>  
> +#include <linux/compiler.h>
> +#include <linux/types.h>
> +
> +
> +/* Valid values for seccomp.mode and prctl(PR_SET_SECCOMP, <mode>) */
> +#define SECCOMP_MODE_DISABLED	0 /* seccomp is not in use. */
> +#define SECCOMP_MODE_STRICT	1 /* uses hard-coded filter. */
> +#define SECCOMP_MODE_FILTER	2 /* uses user-supplied filter. */
> +
> +/*
> + * All BPF programs must return a 32-bit value.
> + * The bottom 16-bits are reserved for future use.
> + * The upper 16-bits are ordered from least permissive values to most.
> + *
> + * The ordering ensures that a min_t() over composed return values always
> + * selects the least permissive choice.
> + */
> +#define SECCOMP_RET_KILL	0x00000000U /* kill the task immediately */
> +#define SECCOMP_RET_ALLOW	0x7fff0000U /* allow */
> +
> +/* Masks for the return value sections. */
> +#define SECCOMP_RET_ACTION	0xffff0000U
> +#define SECCOMP_RET_DATA	0x0000ffffU
> +
> +/**
> + * struct seccomp_data - the format the BPF program executes over.
> + * @nr: the system call number
> + * @arch: indicates system call convention as an AUDIT_ARCH_* value
> + *        as defined in <linux/audit.h>.
> + * @instruction_pointer: at the time of the system call.
> + * @args: up to 6 system call arguments always stored as 64-bit values
> + *        regardless of the architecture.
> + */
> +struct seccomp_data {
> +	int nr;
> +	__u32 arch;
> +	__u64 instruction_pointer;
> +	__u64 args[6];
> +};
>  
> +#ifdef __KERNEL__
>  #ifdef CONFIG_SECCOMP
>  
>  #include <linux/thread_info.h>
>  #include <asm/seccomp.h>
>  
> +struct seccomp_filter;
> +/**
> + * struct seccomp - the state of a seccomp'ed process
> + *
> + * @mode:  indicates one of the valid values above for controlled
> + *         system calls available to a process.
> + * @filter: The metadata and ruleset for determining what system calls
> + *          are allowed for a task.
> + *
> + *          @filter must only be accessed from the context of current as there
> + *          is no locking.
> + */
>  struct seccomp {
>  	int mode;
> +	struct seccomp_filter *filter;
>  };
>  
>  extern void __secure_computing(int);
> @@ -19,7 +72,7 @@ static inline void secure_computing(int this_syscall)
>  }
>  
>  extern long prctl_get_seccomp(void);
> -extern long prctl_set_seccomp(unsigned long);
> +extern long prctl_set_seccomp(unsigned long, char __user *);
>  
>  static inline int seccomp_mode(struct seccomp *s)
>  {
> @@ -31,15 +84,16 @@ static inline int seccomp_mode(struct seccomp *s)
>  #include <linux/errno.h>
>  
>  struct seccomp { };
> +struct seccomp_filter { };
>  
> -#define secure_computing(x) do { } while (0)
> +#define secure_computing(x) 0
>  
>  static inline long prctl_get_seccomp(void)
>  {
>  	return -EINVAL;
>  }
>  
> -static inline long prctl_set_seccomp(unsigned long arg2)
> +static inline long prctl_set_seccomp(unsigned long arg2, char __user *arg3)
>  {
>  	return -EINVAL;
>  }
> @@ -48,7 +102,21 @@ static inline int seccomp_mode(struct seccomp *s)
>  {
>  	return 0;
>  }
> -
>  #endif /* CONFIG_SECCOMP */
>  
> +#ifdef CONFIG_SECCOMP_FILTER
> +extern void put_seccomp_filter(struct task_struct *tsk);
> +extern void get_seccomp_filter(struct task_struct *tsk);
> +extern u32 seccomp_bpf_load(int off);
> +#else  /* CONFIG_SECCOMP_FILTER */
> +static inline void put_seccomp_filter(struct task_struct *tsk)
> +{
> +	return;
> +}
> +static inline void get_seccomp_filter(struct task_struct *tsk)
> +{
> +	return;
> +}
> +#endif /* CONFIG_SECCOMP_FILTER */
> +#endif /* __KERNEL__ */
>  #endif /* _LINUX_SECCOMP_H */
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 26a7a67..4f7a186 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -34,6 +34,7 @@
>  #include <linux/cgroup.h>
>  #include <linux/security.h>
>  #include <linux/hugetlb.h>
> +#include <linux/seccomp.h>
>  #include <linux/swap.h>
>  #include <linux/syscalls.h>
>  #include <linux/jiffies.h>
> @@ -170,6 +171,7 @@ void free_task(struct task_struct *tsk)
>  	free_thread_info(tsk->stack);
>  	rt_mutex_debug_task_free(tsk);
>  	ftrace_graph_exit_task(tsk);
> +	put_seccomp_filter(tsk);
>  	free_task_struct(tsk);
>  }
>  EXPORT_SYMBOL(free_task);
> @@ -1143,6 +1145,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
>  		goto fork_out;
>  
>  	ftrace_graph_init_task(p);
> +	get_seccomp_filter(p);
>  
>  	rt_mutex_init_task(p);
>  
> diff --git a/kernel/seccomp.c b/kernel/seccomp.c
> index e8d76c5..9e50174 100644
> --- a/kernel/seccomp.c
> +++ b/kernel/seccomp.c
> @@ -3,16 +3,338 @@
>   *
>   * Copyright 2004-2005  Andrea Arcangeli <andrea@cpushare.com>
>   *
> - * This defines a simple but solid secure-computing mode.
> + * Copyright (C) 2012 Google, Inc.
> + * Will Drewry <wad@chromium.org>
> + *
> + * This defines a simple but solid secure-computing facility.
> + *
> + * Mode 1 uses a fixed list of allowed system calls.
> + * Mode 2 allows user-defined system call filters in the form
> + *        of Berkeley Packet Filters/Linux Socket Filters.
>   */
>  
> +#include <linux/atomic.h>
>  #include <linux/audit.h>
> -#include <linux/seccomp.h>
> -#include <linux/sched.h>
>  #include <linux/compat.h>
> +#include <linux/filter.h>
> +#include <linux/sched.h>
> +#include <linux/seccomp.h>
> +#include <linux/security.h>
> +#include <linux/slab.h>
> +#include <linux/uaccess.h>
> +
> +#include <linux/tracehook.h>
> +#include <asm/syscall.h>
>  
>  /* #define SECCOMP_DEBUG 1 */
> -#define NR_SECCOMP_MODES 1
> +
> +#ifdef CONFIG_SECCOMP_FILTER
> +/**
> + * struct seccomp_filter - container for seccomp BPF programs
> + *
> + * @usage: reference count to manage the object liftime.
> + *         get/put helpers should be used when accessing an instance
> + *         outside of a lifetime-guarded section.  In general, this
> + *         is only needed for handling filters shared across tasks.
> + * @prev: points to a previously installed, or inherited, filter
> + * @len: the number of instructions in the program
> + * @insns: the BPF program instructions to evaluate
> + *
> + * seccomp_filter objects are organized in a tree linked via the @prev
> + * pointer.  For any task, it appears to be a singly-linked list starting
> + * with current->seccomp.filter, the most recently attached or inherited filter.
> + * However, multiple filters may share a @prev node, by way of fork(), which
> + * results in a unidirectional tree existing in memory.  This is similar to
> + * how namespaces work.
> + *
> + * seccomp_filter objects should never be modified after being attached
> + * to a task_struct (other than @usage).
> + */
> +struct seccomp_filter {
> +	atomic_t usage;
> +	struct seccomp_filter *prev;
> +	unsigned short len;  /* Instruction count */
> +	struct sock_filter insns[];
> +};
> +
> +/* Limit any path through the tree to 256KB worth of instructions. */
> +#define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter))
> +
> +static void seccomp_filter_log_failure(int syscall)
> +{
> +	int compat = 0;
> +#ifdef CONFIG_COMPAT
> +	compat = is_compat_task();
> +#endif
> +	pr_info("%s[%d]: %ssystem call %d blocked at 0x%lx\n",
> +		current->comm, task_pid_nr(current),
> +		(compat ? "compat " : ""),
> +		syscall, KSTK_EIP(current));
> +}
> +

Do we really need to surround is_compat_task() with CNFIG_COMPAT?
It seems that this case has already handled in include/linux/compat.h [1]

> +/**
> + * get_u32 - returns a u32 offset into data
> + * @data: a unsigned 64 bit value
> + * @index: 0 or 1 to return the first or second 32-bits
> + *
> + * This inline exists to hide the length of unsigned long.
> + * If a 32-bit unsigned long is passed in, it will be extended
> + * and the top 32-bits will be 0. If it is a 64-bit unsigned
> + * long, then whatever data is resident will be properly returned.
> + */
> +static inline u32 get_u32(u64 data, int index)
> +{
> +	return ((u32 *)&data)[index];
> +}
> +
> +/* Helper for bpf_load below. */
> +#define BPF_DATA(_name) offsetof(struct seccomp_data, _name)
> +/**
> + * bpf_load: checks and returns a pointer to the requested offset
> + * @off: offset into struct seccomp_data to load from
> + *
> + * Returns the requested 32-bits of data.
> + * seccomp_chk_filter() should assure that @off is 32-bit aligned
> + * and not out of bounds.  Failure to do so is a BUG.
> + */
> +u32 seccomp_bpf_load(int off)
> +{
> +	struct pt_regs *regs = task_pt_regs(current);
> +	if (off == BPF_DATA(nr))
> +		return syscall_get_nr(current, regs);
> +	if (off == BPF_DATA(arch))
> +		return syscall_get_arch(current, regs);
> +	if (off >= BPF_DATA(args[0]) && off < BPF_DATA(args[6])) {
> +		unsigned long value;
> +		int arg = (off - BPF_DATA(args[0])) / sizeof(u64);
> +		int index = !!(off % sizeof(u64));
> +		syscall_get_arguments(current, regs, arg, 1, &value);
> +		return get_u32(value, index);
> +	}
> +	if (off == BPF_DATA(instruction_pointer))
> +		return get_u32(KSTK_EIP(current), 0);
> +	if (off == BPF_DATA(instruction_pointer) + sizeof(u32))
> +		return get_u32(KSTK_EIP(current), 1);
> +	/* seccomp_chk_filter should make this impossible. */
> +	BUG();
> +}
> +
> +/**
> + *	seccomp_chk_filter - verify seccomp filter code
> + *	@filter: filter to verify
> + *	@flen: length of filter
> + *
> + * Takes a previously checked filter (by sk_chk_filter) and
> + * redirects all filter code that loads struct sk_buff data
> + * and related data through seccomp_bpf_load.  It also
> + * enforces length and alignment checking of those loads.
> + *
> + * Returns 0 if the rule set is legal or -EINVAL if not.
> + */
> +static int seccomp_chk_filter(struct sock_filter *filter, unsigned int flen)
> +{
> +	int pc;
> +	for (pc = 0; pc < flen; pc++) {
> +		struct sock_filter *ftest = &filter[pc];
> +		u16 code = ftest->code;
> +		u32 k = ftest->k;
> +		switch (code) {
> +		case BPF_S_LD_W_ABS:
> +			ftest->code = BPF_S_ANC_SECCOMP_LD_W;
> +			/* 32-bit aligned and not out of bounds. */
> +			if (k >= sizeof(struct seccomp_data) || k & 3)
> +				return -EINVAL;
> +			continue;
> +		case BPF_S_LD_W_LEN:
> +			ftest->code = BPF_S_LD_IMM;
> +			ftest->k = sizeof(struct seccomp_data);
> +			continue;
> +		case BPF_S_LDX_W_LEN:
> +			ftest->code = BPF_S_LDX_IMM;
> +			ftest->k = sizeof(struct seccomp_data);
> +			continue;
> +		/* Explicitly include allowed calls. */
> +		case BPF_S_RET_K:
> +		case BPF_S_RET_A:
> +		case BPF_S_ALU_ADD_K:
> +		case BPF_S_ALU_ADD_X:
> +		case BPF_S_ALU_SUB_K:
> +		case BPF_S_ALU_SUB_X:
> +		case BPF_S_ALU_MUL_K:
> +		case BPF_S_ALU_MUL_X:
> +		case BPF_S_ALU_DIV_X:
> +		case BPF_S_ALU_AND_K:
> +		case BPF_S_ALU_AND_X:
> +		case BPF_S_ALU_OR_K:
> +		case BPF_S_ALU_OR_X:
> +		case BPF_S_ALU_LSH_K:
> +		case BPF_S_ALU_LSH_X:
> +		case BPF_S_ALU_RSH_K:
> +		case BPF_S_ALU_RSH_X:
> +		case BPF_S_ALU_NEG:
> +		case BPF_S_LD_IMM:
> +		case BPF_S_LDX_IMM:
> +		case BPF_S_MISC_TAX:
> +		case BPF_S_MISC_TXA:
> +		case BPF_S_ALU_DIV_K:
> +		case BPF_S_LD_MEM:
> +		case BPF_S_LDX_MEM:
> +		case BPF_S_ST:
> +		case BPF_S_STX:
> +		case BPF_S_JMP_JA:
> +		case BPF_S_JMP_JEQ_K:
> +		case BPF_S_JMP_JEQ_X:
> +		case BPF_S_JMP_JGE_K:
> +		case BPF_S_JMP_JGE_X:
> +		case BPF_S_JMP_JGT_K:
> +		case BPF_S_JMP_JGT_X:
> +		case BPF_S_JMP_JSET_K:
> +		case BPF_S_JMP_JSET_X:
> +			continue;
> +		default:
> +			return -EINVAL;
> +		}
> +	}
> +	return 0;
> +}
> +
> +/**
> + * seccomp_run_filters - evaluates all seccomp filters against @syscall
> + * @syscall: number of the current system call
> + *
> + * Returns valid seccomp BPF response codes.
> + */
> +static u32 seccomp_run_filters(int syscall)
> +{
> +	struct seccomp_filter *f;
> +	u32 ret = SECCOMP_RET_KILL;
> +	/*
> +	 * All filters are evaluated in order of youngest to oldest. The lowest
> +	 * BPF return value always takes priority.
> +	 */
> +	for (f = current->seccomp.filter; f; f = f->prev) {
> +		ret = sk_run_filter(NULL, f->insns);
> +		if (ret != SECCOMP_RET_ALLOW)
> +			break;
> +	}
> +	return ret;
> +}
> +
> +/**
> + * seccomp_attach_filter: Attaches a seccomp filter to current.
> + * @fprog: BPF program to install
> + *
> + * Returns 0 on success or an errno on failure.
> + */
> +static long seccomp_attach_filter(struct sock_fprog *fprog)
> +{
> +	struct seccomp_filter *filter;
> +	unsigned long fp_size = fprog->len * sizeof(struct sock_filter);
> +	unsigned long total_insns = fprog->len;
> +	long ret;
> +
> +	if (fprog->len == 0 || fprog->len > BPF_MAXINSNS)
> +		return -EINVAL;
> +
> +	for (filter = current->seccomp.filter; filter; filter = filter->prev)
> +		total_insns += filter->len + 4;  /* include a 4 instr penalty */
> +	if (total_insns > MAX_INSNS_PER_PATH)
> +		return -ENOMEM;
> +
> +	/*
> +	 * Installing a seccomp filter requires that the task have
> +	 * CAP_SYS_ADMIN in its namespace or be running with no_new_privs.
> +	 * This avoids scenarios where unprivileged tasks can affect the
> +	 * behavior of privileged children.
> +	 */
> +	if (!current->no_new_privs &&
> +	    security_capable_noaudit(current_cred(), current_user_ns(),
> +				     CAP_SYS_ADMIN) != 0)
> +		return -EACCES;
> +
> +	/* Allocate a new seccomp_filter */
> +	filter = kzalloc(sizeof(struct seccomp_filter) + fp_size, GFP_KERNEL);
> +	if (!filter)
> +		return -ENOMEM;
> +	atomic_set(&filter->usage, 1);
> +	filter->len = fprog->len;
> +
> +	/* Copy the instructions from fprog. */
> +	ret = -EFAULT;
> +	if (copy_from_user(filter->insns, fprog->filter, fp_size))
> +		goto fail;
> +
> +	/* Check and rewrite the fprog via the skb checker */
> +	ret = sk_chk_filter(filter->insns, filter->len);
> +	if (ret)
> +		goto fail;
> +
> +	/* Check and rewrite the fprog for seccomp use */
> +	ret = seccomp_chk_filter(filter->insns, filter->len);
> +	if (ret)
> +		goto fail;
> +
> +	/*
> +	 * If there is an existing filter, make it the prev and don't drop its
> +	 * task reference.
> +	 */
> +	filter->prev = current->seccomp.filter;
> +	current->seccomp.filter = filter;
> +	return 0;
> +fail:
> +	kfree(filter);
> +	return ret;
> +}
> +
> +/**
> + * seccomp_attach_user_filter - attaches a user-supplied sock_fprog
> + * @user_filter: pointer to the user data containing a sock_fprog.
> + *
> + * Returns 0 on success and non-zero otherwise.
> + */
> +long seccomp_attach_user_filter(char __user *user_filter)
> +{
> +	struct sock_fprog fprog;
> +	long ret = -EFAULT;
> +
> +#ifdef CONFIG_COMPAT
> +	if (is_compat_task()) {
> +		struct compat_sock_fprog fprog32;
> +		if (copy_from_user(&fprog32, user_filter, sizeof(fprog32)))
> +			goto out;
> +		fprog.len = fprog32.len;
> +		fprog.filter = compat_ptr(fprog32.filter);
> +	} else /* falls through to the if below. */
> +#endif
> +	if (copy_from_user(&fprog, user_filter, sizeof(fprog)))
> +		goto out;
> +	ret = seccomp_attach_filter(&fprog);
> +out:
> +	return ret;
> +}

The same note about CONFIG_COMPAT as above.

> +
> +/* get_seccomp_filter - increments the reference count of the filter on @tsk */
> +void get_seccomp_filter(struct task_struct *tsk)
> +{
> +	struct seccomp_filter *orig = tsk->seccomp.filter;
> +	if (!orig)
> +		return;
> +	/* Reference count is bounded by the number of total processes. */
> +	atomic_inc(&orig->usage);
> +}
> +
> +/* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */
> +void put_seccomp_filter(struct task_struct *tsk)
> +{
> +	struct seccomp_filter *orig = tsk->seccomp.filter;
> +	/* Clean up single-reference branches iteratively. */
> +	while (orig && atomic_dec_and_test(&orig->usage)) {
> +		struct seccomp_filter *freeme = orig;
> +		orig = orig->prev;
> +		kfree(freeme);
> +	}
> +}
> +#endif	/* CONFIG_SECCOMP_FILTER */
>  
>  /*
>   * Secure computing mode 1 allows only read/write/exit/sigreturn.
> @@ -34,10 +356,11 @@ static int mode1_syscalls_32[] = {
>  void __secure_computing(int this_syscall)
>  {
>  	int mode = current->seccomp.mode;
> -	int * syscall;
> +	int exit_sig = 0;
> +	int *syscall;
>  
>  	switch (mode) {
> -	case 1:
> +	case SECCOMP_MODE_STRICT:
>  		syscall = mode1_syscalls;
>  #ifdef CONFIG_COMPAT
>  		if (is_compat_task())
> @@ -47,7 +370,16 @@ void __secure_computing(int this_syscall)
>  			if (*syscall == this_syscall)
>  				return;
>  		} while (*++syscall);
> +		exit_sig = SIGKILL;
> +		break;
> +#ifdef CONFIG_SECCOMP_FILTER
> +	case SECCOMP_MODE_FILTER:
> +		if (seccomp_run_filters(this_syscall) == SECCOMP_RET_ALLOW)
> +			return;
> +		seccomp_filter_log_failure(this_syscall);
> +		exit_sig = SIGSYS;
>  		break;
> +#endif
>  	default:
>  		BUG();
>  	}
> @@ -56,7 +388,7 @@ void __secure_computing(int this_syscall)
>  	dump_stack();
>  #endif
>  	audit_seccomp(this_syscall);
> -	do_exit(SIGKILL);
> +	do_exit(exit_sig);
>  }
>  
>  long prctl_get_seccomp(void)
> @@ -64,25 +396,48 @@ long prctl_get_seccomp(void)
>  	return current->seccomp.mode;
>  }
>  
> -long prctl_set_seccomp(unsigned long seccomp_mode)
> +/**
> + * prctl_set_seccomp: configures current->seccomp.mode
> + * @seccomp_mode: requested mode to use
> + * @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER
> + *
> + * This function may be called repeatedly with a @seccomp_mode of
> + * SECCOMP_MODE_FILTER to install additional filters.  Every filter
> + * successfully installed will be evaluated (in reverse order) for each system
> + * call the task makes.
> + *
> + * Once current->seccomp.mode is non-zero, it may not be changed.
> + *
> + * Returns 0 on success or -EINVAL on failure.
> + */
> +long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter)
>  {
> -	long ret;
> +	long ret = -EINVAL;
>  
> -	/* can set it only once to be even more secure */
> -	ret = -EPERM;
> -	if (unlikely(current->seccomp.mode))
> +	if (current->seccomp.mode &&
> +	    current->seccomp.mode != seccomp_mode)
>  		goto out;
>  
> -	ret = -EINVAL;
> -	if (seccomp_mode && seccomp_mode <= NR_SECCOMP_MODES) {
> -		current->seccomp.mode = seccomp_mode;
> -		set_thread_flag(TIF_SECCOMP);
> +	switch (seccomp_mode) {
> +	case SECCOMP_MODE_STRICT:
> +		ret = 0;
>  #ifdef TIF_NOTSC
>  		disable_TSC();
>  #endif
> -		ret = 0;
> +		break;
> +#ifdef CONFIG_SECCOMP_FILTER
> +	case SECCOMP_MODE_FILTER:
> +		ret = seccomp_attach_user_filter(filter);
> +		if (ret)
> +			goto out;
> +		break;
> +#endif
> +	default:
> +		goto out;
>  	}
>  
> - out:
> +	current->seccomp.mode = seccomp_mode;
> +	set_thread_flag(TIF_SECCOMP);
> +out:
>  	return ret;
>  }
> diff --git a/kernel/sys.c b/kernel/sys.c
> index 12e862a..038e6b7 100644
> --- a/kernel/sys.c
> +++ b/kernel/sys.c
> @@ -1899,7 +1899,7 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
>  			error = prctl_get_seccomp();
>  			break;
>  		case PR_SET_SECCOMP:
> -			error = prctl_set_seccomp(arg2);
> +			error = prctl_set_seccomp(arg2, (char __user *)arg3);
>  			break;
>  		case PR_GET_TSC:
>  			error = GET_TSC_CTL(arg2);
> -- 
> 1.7.5.4
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-arch" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

[1] http://lxr.linux.no/#linux+v3.3/include/linux/compat.h#L566

Best wishes
Vladimir Murzin

Re: [PATCH v15 04/13] arch/x86: add syscall_get_arch to syscall.h

[H. Peter Anvin]

On 03/14/2012 08:11 PM, Will Drewry wrote:
>  
> +static inline int syscall_get_arch(struct task_struct *task,
> +				   struct pt_regs *regs)
> +{
> +#ifdef CONFIG_IA32_EMULATION
> +	/*
> +	 * TS_COMPAT is set for 32-bit syscall entries and then
> +	 * remains set until we return to user mode.
> +	 *
> +	 * TIF_IA32 tasks should always have TS_COMPAT set at
> +	 * system call time.
> +	 */
> +	if (task_thread_info(task)->status & TS_COMPAT)
> +		return AUDIT_ARCH_I386;
> +#endif
> +	return AUDIT_ARCH_X86_64;
> +}
>  #endif	/* CONFIG_X86_32 */
>  
>  #endif	/* _ASM_X86_SYSCALL_H */

Just one FYI on this: after the x32 changes are upstream this can be
implemented in terms of is_ia32_task().

	-hpa

[kernel-hardening] Re: [PATCH v15 04/13] arch/x86: add syscall_get_arch to syscall.h

[H. Peter Anvin]

On 03/14/2012 08:11 PM, Will Drewry wrote:
>  
> +static inline int syscall_get_arch(struct task_struct *task,
> +				   struct pt_regs *regs)
> +{
> +#ifdef CONFIG_IA32_EMULATION
> +	/*
> +	 * TS_COMPAT is set for 32-bit syscall entries and then
> +	 * remains set until we return to user mode.
> +	 *
> +	 * TIF_IA32 tasks should always have TS_COMPAT set at
> +	 * system call time.
> +	 */
> +	if (task_thread_info(task)->status & TS_COMPAT)
> +		return AUDIT_ARCH_I386;
> +#endif
> +	return AUDIT_ARCH_X86_64;
> +}
>  #endif	/* CONFIG_X86_32 */
>  
>  #endif	/* _ASM_X86_SYSCALL_H */

Just one FYI on this: after the x32 changes are upstream this can be
implemented in terms of is_ia32_task().

	-hpa

Re: [PATCH v15 00/13] seccomp_filter: syscall filtering using BPF

[H. Peter Anvin]

On 03/14/2012 08:11 PM, Will Drewry wrote:
> Please see prior revisions of this patch series for a high
> level blurb.
> 
> This revision makes a number of refinements and tweaks. The biggest
> change is a slight renumbering of the return codes which will break
> existing code using this patch series.
> 
> I believe this patch is in good shape, and I don't see the need for
> any more API changes at this point.  I plan to start using this revision
> more extensively, and I'd certainly appreciate any testing.
> 
> Thanks!
> will
> 

x86 portions:

Reviewed-by: H. Peter Anvin <hpa@zytor.com>

What is the preferred way to push this upstream?  (Presumably for 3.5 at
this point, but we should get it into -next as soon as possible after
the merge window.)

	-hpa

[kernel-hardening] Re: [PATCH v15 00/13] seccomp_filter: syscall filtering using BPF

[H. Peter Anvin]

On 03/14/2012 08:11 PM, Will Drewry wrote:
> Please see prior revisions of this patch series for a high
> level blurb.
> 
> This revision makes a number of refinements and tweaks. The biggest
> change is a slight renumbering of the return codes which will break
> existing code using this patch series.
> 
> I believe this patch is in good shape, and I don't see the need for
> any more API changes at this point.  I plan to start using this revision
> more extensively, and I'd certainly appreciate any testing.
> 
> Thanks!
> will
> 

x86 portions:

Reviewed-by: H. Peter Anvin <hpa@zytor.com>

What is the preferred way to push this upstream?  (Presumably for 3.5 at
this point, but we should get it into -next as soon as possible after
the merge window.)

	-hpa

Re: [PATCH v15 00/13] seccomp_filter: syscall filtering using BPF

[Will Drewry]

On Sun, Mar 25, 2012 at 2:36 PM, H. Peter Anvin <hpa@zytor.com> wrote:
> On 03/14/2012 08:11 PM, Will Drewry wrote:
>> Please see prior revisions of this patch series for a high
>> level blurb.
>>
>> This revision makes a number of refinements and tweaks. The biggest
>> change is a slight renumbering of the return codes which will break
>> existing code using this patch series.
>>
>> I believe this patch is in good shape, and I don't see the need for
>> any more API changes at this point.  I plan to start using this revision
>> more extensively, and I'd certainly appreciate any testing.
>>
>> Thanks!
>> will
>>
>
> x86 portions:
>
> Reviewed-by: H. Peter Anvin <hpa@zytor.com>

Thanks!

> What is the preferred way to push this upstream?  (Presumably for 3.5 at
> this point, but we should get it into -next as soon as possible after
> the merge window.)

A repost when rc1 has been cut is what's been suggested to me.

Additionally, two tweaks have been pointed out off list (documentation
cruft and lack if #ifdef for asm/syscall.h), which I have fixed in my
local and github tree but haven't yet reposted here.  I was planning
on just posting v17 when rc1 is cut (unless I've blithely missed it
already) and then trying to pester everyone and anyone who can merge.
:)

Maybe someone more authoritative than me will answer though.

thanks!
will

[kernel-hardening] Re: [PATCH v15 00/13] seccomp_filter: syscall filtering using BPF

[Will Drewry]

On Sun, Mar 25, 2012 at 2:36 PM, H. Peter Anvin <hpa@zytor.com> wrote:
> On 03/14/2012 08:11 PM, Will Drewry wrote:
>> Please see prior revisions of this patch series for a high
>> level blurb.
>>
>> This revision makes a number of refinements and tweaks. The biggest
>> change is a slight renumbering of the return codes which will break
>> existing code using this patch series.
>>
>> I believe this patch is in good shape, and I don't see the need for
>> any more API changes at this point.  I plan to start using this revision
>> more extensively, and I'd certainly appreciate any testing.
>>
>> Thanks!
>> will
>>
>
> x86 portions:
>
> Reviewed-by: H. Peter Anvin <hpa@zytor.com>

Thanks!

> What is the preferred way to push this upstream?  (Presumably for 3.5 at
> this point, but we should get it into -next as soon as possible after
> the merge window.)

A repost when rc1 has been cut is what's been suggested to me.

Additionally, two tweaks have been pointed out off list (documentation
cruft and lack if #ifdef for asm/syscall.h), which I have fixed in my
local and github tree but haven't yet reposted here.  I was planning
on just posting v17 when rc1 is cut (unless I've blithely missed it
already) and then trying to pester everyone and anyone who can merge.
:)

Maybe someone more authoritative than me will answer though.

thanks!
will

Re: [PATCH v15 04/13] arch/x86: add syscall_get_arch to syscall.h

[Will Drewry]

On Sun, Mar 25, 2012 at 2:34 PM, H. Peter Anvin <hpa@zytor.com> wrote:
> On 03/14/2012 08:11 PM, Will Drewry wrote:
>>
>> +static inline int syscall_get_arch(struct task_struct *task,
>> +                                struct pt_regs *regs)
>> +{
>> +#ifdef CONFIG_IA32_EMULATION
>> +     /*
>> +      * TS_COMPAT is set for 32-bit syscall entries and then
>> +      * remains set until we return to user mode.
>> +      *
>> +      * TIF_IA32 tasks should always have TS_COMPAT set at
>> +      * system call time.
>> +      */
>> +     if (task_thread_info(task)->status & TS_COMPAT)
>> +             return AUDIT_ARCH_I386;
>> +#endif
>> +     return AUDIT_ARCH_X86_64;
>> +}
>>  #endif       /* CONFIG_X86_32 */
>>
>>  #endif       /* _ASM_X86_SYSCALL_H */
>
> Just one FYI on this: after the x32 changes are upstream this can be
> implemented in terms of is_ia32_task().

Now that I've seen is_ia32_task(), it appears to be exactly the same as above:
(1)  If we're x86_32, it's ia32
(2)  If we're x86_64, ia32 == !!(status & TS_COMPAT)
(3)  Otherwise, it's x86_64, including x32

Am I missing something? Should is_ia32_task(void) take a task_struct?
Right now, I don't see any reason to change the code, as posted, but
maybe I am mis-reading?

thanks!
will

[kernel-hardening] Re: [PATCH v15 04/13] arch/x86: add syscall_get_arch to syscall.h

[Will Drewry]

On Sun, Mar 25, 2012 at 2:34 PM, H. Peter Anvin <hpa@zytor.com> wrote:
> On 03/14/2012 08:11 PM, Will Drewry wrote:
>>
>> +static inline int syscall_get_arch(struct task_struct *task,
>> +                                struct pt_regs *regs)
>> +{
>> +#ifdef CONFIG_IA32_EMULATION
>> +     /*
>> +      * TS_COMPAT is set for 32-bit syscall entries and then
>> +      * remains set until we return to user mode.
>> +      *
>> +      * TIF_IA32 tasks should always have TS_COMPAT set at
>> +      * system call time.
>> +      */
>> +     if (task_thread_info(task)->status & TS_COMPAT)
>> +             return AUDIT_ARCH_I386;
>> +#endif
>> +     return AUDIT_ARCH_X86_64;
>> +}
>>  #endif       /* CONFIG_X86_32 */
>>
>>  #endif       /* _ASM_X86_SYSCALL_H */
>
> Just one FYI on this: after the x32 changes are upstream this can be
> implemented in terms of is_ia32_task().

Now that I've seen is_ia32_task(), it appears to be exactly the same as above:
(1)  If we're x86_32, it's ia32
(2)  If we're x86_64, ia32 == !!(status & TS_COMPAT)
(3)  Otherwise, it's x86_64, including x32

Am I missing something? Should is_ia32_task(void) take a task_struct?
Right now, I don't see any reason to change the code, as posted, but
maybe I am mis-reading?

thanks!
will

Re: [PATCH v15 04/13] arch/x86: add syscall_get_arch to syscall.h

[H. Peter Anvin]

On 04/10/2012 08:13 PM, Will Drewry wrote:
> 
> Now that I've seen is_ia32_task(), it appears to be exactly the same as above:
> (1)  If we're x86_32, it's ia32
> (2)  If we're x86_64, ia32 == !!(status & TS_COMPAT)
> (3)  Otherwise, it's x86_64, including x32
> 
> Am I missing something? Should is_ia32_task(void) take a task_struct?
> Right now, I don't see any reason to change the code, as posted, but
> maybe I am mis-reading?
> 

is_compat_task() is true for x32, is_ia32_task() is false.

	-hpa

[kernel-hardening] Re: [PATCH v15 04/13] arch/x86: add syscall_get_arch to syscall.h

[H. Peter Anvin]

On 04/10/2012 08:13 PM, Will Drewry wrote:
> 
> Now that I've seen is_ia32_task(), it appears to be exactly the same as above:
> (1)  If we're x86_32, it's ia32
> (2)  If we're x86_64, ia32 == !!(status & TS_COMPAT)
> (3)  Otherwise, it's x86_64, including x32
> 
> Am I missing something? Should is_ia32_task(void) take a task_struct?
> Right now, I don't see any reason to change the code, as posted, but
> maybe I am mis-reading?
> 

is_compat_task() is true for x32, is_ia32_task() is false.

	-hpa

Re: [PATCH v15 04/13] arch/x86: add syscall_get_arch to syscall.h

[H. Peter Anvin]

On 04/10/2012 08:13 PM, Will Drewry wrote:
> On Sun, Mar 25, 2012 at 2:34 PM, H. Peter Anvin <hpa@zytor.com> wrote:
>> On 03/14/2012 08:11 PM, Will Drewry wrote:
>>>
>>> +static inline int syscall_get_arch(struct task_struct *task,
>>> +                                struct pt_regs *regs)
>>> +{
>>> +#ifdef CONFIG_IA32_EMULATION
>>> +     /*
>>> +      * TS_COMPAT is set for 32-bit syscall entries and then
>>> +      * remains set until we return to user mode.
>>> +      *
>>> +      * TIF_IA32 tasks should always have TS_COMPAT set at
>>> +      * system call time.
>>> +      */
>>> +     if (task_thread_info(task)->status & TS_COMPAT)
>>> +             return AUDIT_ARCH_I386;
>>> +#endif
>>> +     return AUDIT_ARCH_X86_64;
>>> +}
>>>  #endif       /* CONFIG_X86_32 */
>>>
>>>  #endif       /* _ASM_X86_SYSCALL_H */
>>
>> Just one FYI on this: after the x32 changes are upstream this can be
>> implemented in terms of is_ia32_task().
> 
> Now that I've seen is_ia32_task(), it appears to be exactly the same as above:
> (1)  If we're x86_32, it's ia32
> (2)  If we're x86_64, ia32 == !!(status & TS_COMPAT)
> (3)  Otherwise, it's x86_64, including x32
> 
> Am I missing something? Should is_ia32_task(void) take a task_struct?
> Right now, I don't see any reason to change the code, as posted, but
> maybe I am mis-reading?
> 

Sorry, answered the wrong question.  Yes, it is the same as above...
just wandered if we could centralize this test.  It might indeed make
sense to provide general predicates which take a task pointer.

	-hpa

[kernel-hardening] Re: [PATCH v15 04/13] arch/x86: add syscall_get_arch to syscall.h

[H. Peter Anvin]

On 04/10/2012 08:13 PM, Will Drewry wrote:
> On Sun, Mar 25, 2012 at 2:34 PM, H. Peter Anvin <hpa@zytor.com> wrote:
>> On 03/14/2012 08:11 PM, Will Drewry wrote:
>>>
>>> +static inline int syscall_get_arch(struct task_struct *task,
>>> +                                struct pt_regs *regs)
>>> +{
>>> +#ifdef CONFIG_IA32_EMULATION
>>> +     /*
>>> +      * TS_COMPAT is set for 32-bit syscall entries and then
>>> +      * remains set until we return to user mode.
>>> +      *
>>> +      * TIF_IA32 tasks should always have TS_COMPAT set at
>>> +      * system call time.
>>> +      */
>>> +     if (task_thread_info(task)->status & TS_COMPAT)
>>> +             return AUDIT_ARCH_I386;
>>> +#endif
>>> +     return AUDIT_ARCH_X86_64;
>>> +}
>>>  #endif       /* CONFIG_X86_32 */
>>>
>>>  #endif       /* _ASM_X86_SYSCALL_H */
>>
>> Just one FYI on this: after the x32 changes are upstream this can be
>> implemented in terms of is_ia32_task().
> 
> Now that I've seen is_ia32_task(), it appears to be exactly the same as above:
> (1)  If we're x86_32, it's ia32
> (2)  If we're x86_64, ia32 == !!(status & TS_COMPAT)
> (3)  Otherwise, it's x86_64, including x32
> 
> Am I missing something? Should is_ia32_task(void) take a task_struct?
> Right now, I don't see any reason to change the code, as posted, but
> maybe I am mis-reading?
> 

Sorry, answered the wrong question.  Yes, it is the same as above...
just wandered if we could centralize this test.  It might indeed make
sense to provide general predicates which take a task pointer.

	-hpa

Re: [PATCH v15 04/13] arch/x86: add syscall_get_arch to syscall.h

[Will Drewry]

On Tue, Apr 10, 2012 at 10:20 PM, H. Peter Anvin <hpa@zytor.com> wrote:
> On 04/10/2012 08:13 PM, Will Drewry wrote:
>> On Sun, Mar 25, 2012 at 2:34 PM, H. Peter Anvin <hpa@zytor.com> wrote:
>>> On 03/14/2012 08:11 PM, Will Drewry wrote:
>>>>
>>>> +static inline int syscall_get_arch(struct task_struct *task,
>>>> +                                struct pt_regs *regs)
>>>> +{
>>>> +#ifdef CONFIG_IA32_EMULATION
>>>> +     /*
>>>> +      * TS_COMPAT is set for 32-bit syscall entries and then
>>>> +      * remains set until we return to user mode.
>>>> +      *
>>>> +      * TIF_IA32 tasks should always have TS_COMPAT set at
>>>> +      * system call time.
>>>> +      */
>>>> +     if (task_thread_info(task)->status & TS_COMPAT)
>>>> +             return AUDIT_ARCH_I386;
>>>> +#endif
>>>> +     return AUDIT_ARCH_X86_64;
>>>> +}
>>>>  #endif       /* CONFIG_X86_32 */
>>>>
>>>>  #endif       /* _ASM_X86_SYSCALL_H */
>>>
>>> Just one FYI on this: after the x32 changes are upstream this can be
>>> implemented in terms of is_ia32_task().
>>
>> Now that I've seen is_ia32_task(), it appears to be exactly the same as above:
>> (1)  If we're x86_32, it's ia32
>> (2)  If we're x86_64, ia32 == !!(status & TS_COMPAT)
>> (3)  Otherwise, it's x86_64, including x32
>>
>> Am I missing something? Should is_ia32_task(void) take a task_struct?
>> Right now, I don't see any reason to change the code, as posted, but
>> maybe I am mis-reading?
>>
>
> Sorry, answered the wrong question.  Yes, it is the same as above...
> just wandered if we could centralize this test.  It might indeed make
> sense to provide general predicates which take a task pointer.

Makes sense to me. I'm leaving this specific patch alone at present.

That said, a quick grep shows only  a handful of ia32 references:
./arch/x86/include/asm/compat.h:        return is_ia32_task() || is_x32_task();
./arch/x86/ia32/ia32_signal.c:  bool ia32 = is_ia32_task();
./arch/x86/kernel/ptrace.c:     if (!is_ia32_task())

Would it make sense to make a new predicate or just expand the one
added in 3.4 to take a task_struct parameter? I'm not sure if there'd
be much fallout in converting these from directly checking
current_thread_info to task_thread_info.

It's a small patch either way.

cheers!
will

[kernel-hardening] Re: [PATCH v15 04/13] arch/x86: add syscall_get_arch to syscall.h

[Will Drewry]

On Tue, Apr 10, 2012 at 10:20 PM, H. Peter Anvin <hpa@zytor.com> wrote:
> On 04/10/2012 08:13 PM, Will Drewry wrote:
>> On Sun, Mar 25, 2012 at 2:34 PM, H. Peter Anvin <hpa@zytor.com> wrote:
>>> On 03/14/2012 08:11 PM, Will Drewry wrote:
>>>>
>>>> +static inline int syscall_get_arch(struct task_struct *task,
>>>> +                                struct pt_regs *regs)
>>>> +{
>>>> +#ifdef CONFIG_IA32_EMULATION
>>>> +     /*
>>>> +      * TS_COMPAT is set for 32-bit syscall entries and then
>>>> +      * remains set until we return to user mode.
>>>> +      *
>>>> +      * TIF_IA32 tasks should always have TS_COMPAT set at
>>>> +      * system call time.
>>>> +      */
>>>> +     if (task_thread_info(task)->status & TS_COMPAT)
>>>> +             return AUDIT_ARCH_I386;
>>>> +#endif
>>>> +     return AUDIT_ARCH_X86_64;
>>>> +}
>>>>  #endif       /* CONFIG_X86_32 */
>>>>
>>>>  #endif       /* _ASM_X86_SYSCALL_H */
>>>
>>> Just one FYI on this: after the x32 changes are upstream this can be
>>> implemented in terms of is_ia32_task().
>>
>> Now that I've seen is_ia32_task(), it appears to be exactly the same as above:
>> (1)  If we're x86_32, it's ia32
>> (2)  If we're x86_64, ia32 == !!(status & TS_COMPAT)
>> (3)  Otherwise, it's x86_64, including x32
>>
>> Am I missing something? Should is_ia32_task(void) take a task_struct?
>> Right now, I don't see any reason to change the code, as posted, but
>> maybe I am mis-reading?
>>
>
> Sorry, answered the wrong question.  Yes, it is the same as above...
> just wandered if we could centralize this test.  It might indeed make
> sense to provide general predicates which take a task pointer.

Makes sense to me. I'm leaving this specific patch alone at present.

That said, a quick grep shows only  a handful of ia32 references:
./arch/x86/include/asm/compat.h:        return is_ia32_task() || is_x32_task();
./arch/x86/ia32/ia32_signal.c:  bool ia32 = is_ia32_task();
./arch/x86/kernel/ptrace.c:     if (!is_ia32_task())

Would it make sense to make a new predicate or just expand the one
added in 3.4 to take a task_struct parameter? I'm not sure if there'd
be much fallout in converting these from directly checking
current_thread_info to task_thread_info.

It's a small patch either way.

cheers!
will