[PATCH v2 0/3] Checkpoint Support for Syscall User Dispatch

[PATCH v2 0/3] Checkpoint Support for Syscall User Dispatch

[Gregory Price]

v2: Implements the getter/setter interface in ptrace rather than prctl

Syscall user dispatch makes it possible to cleanly intercept system
calls from user-land.  However, most transparent checkpoint software
presently leverages some combination of ptrace and system call
injection to place software in a ready-to-checkpoint state.

If Syscall User Dispatch is enabled at the time of being quiesced,
injected system calls will subsequently be interposed upon and
dispatched to the task's signal handler.

This patch set implements 3 features to enable software such as CRIU
to cleanly interpose upon software leveraging syscall user dispatch.

- Implement PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH, akin to a similar
  feature for SECCOMP.  This allows a ptracer to temporarily disable
  syscall user dispatch, making syscall injection possible.

- Implement an fs/proc extension that reports whether Syscall User
  Dispatch is being used in proc/status.  A similar value is present
  for SECCOMP, and is used to determine whether special logic is
  needed during checkpoint/resume.

- Implement a getter interface for Syscall User Dispatch config info.
  To resume successfully, the checkpoint/resume software has to
  save and restore this information.  Presently this configuration
  is write-only, with no way for C/R software to save it.
	This was done in ptrace because syscall user dispatch is not part of
  uapi.  The syscall_user_dispatch_config structure was added to the
  ptrace exports.


Signed-off-by: Gregory Price <gregory.price@memverge.com>

Gregory Price (3):
  ptrace,syscall_user_dispatch: Implement Syscall User Dispatch
    Suspension
  fs/proc/array: Add Syscall User Dispatch to proc status
  ptrace,syscall_user_dispatch: add a getter/setter for sud
    configuration

 .../admin-guide/syscall-user-dispatch.rst     |  5 +-
 fs/proc/array.c                               |  8 +++
 include/linux/ptrace.h                        |  2 +
 include/linux/syscall_user_dispatch.h         | 19 +++++++
 include/uapi/linux/ptrace.h                   | 16 +++++-
 kernel/entry/syscall_user_dispatch.c          | 54 +++++++++++++++++++
 kernel/ptrace.c                               | 14 +++++
 7 files changed, 116 insertions(+), 2 deletions(-)

-- 
2.39.0

[PATCH 1/3] ptrace,syscall_user_dispatch: Implement Syscall User Dispatch Suspension

[Gregory Price]

Adds PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH to ptrace options, and
modify Syscall User Dispatch to suspend interception when enabled.

This is modeled after the SUSPEND_SECCOMP feature, which suspends
SECCOMP interposition.  Without doing this, software like CRIU will
inject system calls into a process and be intercepted by Syscall
User Dispatch, either causing a crash (due to blocked signals) or
the delivery of those signals to a ptracer (not the intended behavior).

Since Syscall User Dispatch is not a privileged feature, a check
for permissions is not required, however attempting to set this
option when CONFIG_CHECKPOINT_RESTORE it not supported should be
disallowed, as its intended use is checkpoint/resume.

Signed-off-by: Gregory Price <gregory.price@memverge.com>
---
 include/linux/ptrace.h               | 2 ++
 include/uapi/linux/ptrace.h          | 6 +++++-
 kernel/entry/syscall_user_dispatch.c | 5 +++++
 kernel/ptrace.c                      | 5 +++++
 4 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index eaaef3ffec22..461ae5c99d57 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -45,6 +45,8 @@ extern int ptrace_access_vm(struct task_struct *tsk, unsigned long addr,
 
 #define PT_EXITKILL		(PTRACE_O_EXITKILL << PT_OPT_FLAG_SHIFT)
 #define PT_SUSPEND_SECCOMP	(PTRACE_O_SUSPEND_SECCOMP << PT_OPT_FLAG_SHIFT)
+#define PT_SUSPEND_SYSCALL_USER_DISPATCH \
+	(PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH << PT_OPT_FLAG_SHIFT)
 
 extern long arch_ptrace(struct task_struct *child, long request,
 			unsigned long addr, unsigned long data);
diff --git a/include/uapi/linux/ptrace.h b/include/uapi/linux/ptrace.h
index 195ae64a8c87..ba9e3f19a22c 100644
--- a/include/uapi/linux/ptrace.h
+++ b/include/uapi/linux/ptrace.h
@@ -146,9 +146,13 @@ struct ptrace_rseq_configuration {
 /* eventless options */
 #define PTRACE_O_EXITKILL		(1 << 20)
 #define PTRACE_O_SUSPEND_SECCOMP	(1 << 21)
+#define PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH	(1 << 22)
 
 #define PTRACE_O_MASK		(\
-	0x000000ff | PTRACE_O_EXITKILL | PTRACE_O_SUSPEND_SECCOMP)
+	0x000000ff | \
+	PTRACE_O_EXITKILL | \
+	PTRACE_O_SUSPEND_SECCOMP | \
+	PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH)
 
 #include <asm/ptrace.h>
 
diff --git a/kernel/entry/syscall_user_dispatch.c b/kernel/entry/syscall_user_dispatch.c
index 0b6379adff6b..7607f4598dd8 100644
--- a/kernel/entry/syscall_user_dispatch.c
+++ b/kernel/entry/syscall_user_dispatch.c
@@ -8,6 +8,7 @@
 #include <linux/uaccess.h>
 #include <linux/signal.h>
 #include <linux/elf.h>
+#include <linux/ptrace.h>
 
 #include <linux/sched/signal.h>
 #include <linux/sched/task_stack.h>
@@ -36,6 +37,10 @@ bool syscall_user_dispatch(struct pt_regs *regs)
 	struct syscall_user_dispatch *sd = &current->syscall_dispatch;
 	char state;
 
+	if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
+		unlikely(current->ptrace & PT_SUSPEND_SYSCALL_USER_DISPATCH))
+		return false;
+
 	if (likely(instruction_pointer(regs) - sd->offset < sd->len))
 		return false;
 
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 54482193e1ed..a6ad815bd4be 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -370,6 +370,11 @@ static int check_ptrace_options(unsigned long data)
 	if (data & ~(unsigned long)PTRACE_O_MASK)
 		return -EINVAL;
 
+	if (unlikely(data & PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH)) {
+		if (!IS_ENABLED(CONFIG_CHECKPOINT_RESTART))
+			return -EINVAL;
+	}
+
 	if (unlikely(data & PTRACE_O_SUSPEND_SECCOMP)) {
 		if (!IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) ||
 		    !IS_ENABLED(CONFIG_SECCOMP))
-- 
2.39.0

[PATCH 2/3] fs/proc/array: Add Syscall User Dispatch to proc status

[Gregory Price]

If a dispatch selector has been configured for Syscall User Dispatch,
report Syscall User Dispath as configured in proc/status.

This provides an indicator to userland checkpoint/restart software that
it much manage special signal conditions (similar to SECCOMP)

Signed-off-by: Gregory Price <gregory.price@memverge.com>
---
 fs/proc/array.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 49283b8103c7..c85cdb4c137c 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -428,6 +428,13 @@ static inline void task_thp_status(struct seq_file *m, struct mm_struct *mm)
 	seq_printf(m, "THP_enabled:\t%d\n", thp_enabled);
 }
 
+static inline void task_syscall_user_dispatch(struct seq_file *m,
+						struct task_struct *p)
+{
+	seq_put_decimal_ull(m, "\nSyscall_user_dispatch:\t",
+			    (p->syscall_dispatch.selector != NULL));
+}
+
 int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
 			struct pid *pid, struct task_struct *task)
 {
@@ -451,6 +458,7 @@ int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
 	task_cpus_allowed(m, task);
 	cpuset_task_status_allowed(m, task);
 	task_context_switch_counts(m, task);
+	task_syscall_user_dispatch(m, task);
 	return 0;
 }
 
-- 
2.39.0

[PATCH 3/3] ptrace,syscall_user_dispatch: add a getter/setter for sud configuration

[Gregory Price]

This patch implements ptrace getter and setter interface for syscall
syscall user dispatch configuration info.

Presently, these settings are write-only via prctl, making it impossible
to implement transparent checkpoint.

This is modeled after a similar interface for SECCOMP, which can have
its configuration dumped by ptrace for software like CRIU.

Signed-off-by: Gregory Price <gregory.price@memverge.com>
---
 .../admin-guide/syscall-user-dispatch.rst     |  5 +-
 include/linux/syscall_user_dispatch.h         | 19 +++++++
 include/uapi/linux/ptrace.h                   | 10 ++++
 kernel/entry/syscall_user_dispatch.c          | 49 +++++++++++++++++++
 kernel/ptrace.c                               |  9 ++++
 5 files changed, 91 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/syscall-user-dispatch.rst b/Documentation/admin-guide/syscall-user-dispatch.rst
index 60314953c728..a23ae21a1d5b 100644
--- a/Documentation/admin-guide/syscall-user-dispatch.rst
+++ b/Documentation/admin-guide/syscall-user-dispatch.rst
@@ -43,7 +43,10 @@ doesn't rely on any of the syscall ABI to make the filtering.  It uses
 only the syscall dispatcher address and the userspace key.
 
 As the ABI of these intercepted syscalls is unknown to Linux, these
-syscalls are not instrumentable via ptrace or the syscall tracepoints.
+syscalls are not instrumentable via ptrace or the syscall tracepoints,
+however an interfaces to suspend, checkpoint, and restore syscall user
+dispatch configuration has been added to ptrace to assist userland
+checkpoint/restart software.
 
 Interface
 ---------
diff --git a/include/linux/syscall_user_dispatch.h b/include/linux/syscall_user_dispatch.h
index a0ae443fb7df..dbf384b7a26e 100644
--- a/include/linux/syscall_user_dispatch.h
+++ b/include/linux/syscall_user_dispatch.h
@@ -22,6 +22,13 @@ int set_syscall_user_dispatch(unsigned long mode, unsigned long offset,
 #define clear_syscall_work_syscall_user_dispatch(tsk) \
 	clear_task_syscall_work(tsk, SYSCALL_USER_DISPATCH)
 
+int syscall_user_dispatch_get_config(struct task_struct *task, unsigned long size,
+	void __user *data);
+
+int syscall_user_dispatch_set_config(struct task_struct *task, unsigned long size,
+	void __user *data);
+
+
 #else
 struct syscall_user_dispatch {};
 
@@ -35,6 +42,18 @@ static inline void clear_syscall_work_syscall_user_dispatch(struct task_struct *
 {
 }
 
+int syscall_user_dispatch_get_config(struct task_struct *task, unsigned long size,
+	void __user *data)
+{
+	return -EINVAL;
+}
+
+int syscall_user_dispatch_set_config(struct task_struct *task, unsigned long size,
+	void __user *data)
+{
+	return -EINVAL;
+}
+
 #endif /* CONFIG_GENERIC_ENTRY */
 
 #endif /* _SYSCALL_USER_DISPATCH_H */
diff --git a/include/uapi/linux/ptrace.h b/include/uapi/linux/ptrace.h
index ba9e3f19a22c..8b93c78189b5 100644
--- a/include/uapi/linux/ptrace.h
+++ b/include/uapi/linux/ptrace.h
@@ -112,6 +112,16 @@ struct ptrace_rseq_configuration {
 	__u32 pad;
 };
 
+#define PTRACE_SET_SYSCALL_USER_DISPATCH_CONFIG 0x4210
+#define PTRACE_GET_SYSCALL_USER_DISPATCH_CONFIG 0x4211
+struct syscall_user_dispatch_config {
+	__u64 mode;
+	__s8 *selector;
+	__u64 offset;
+	__u64 len;
+	__u8 on_dispatch;
+};
+
 /*
  * These values are stored in task->ptrace_message
  * by ptrace_stop to describe the current syscall-stop.
diff --git a/kernel/entry/syscall_user_dispatch.c b/kernel/entry/syscall_user_dispatch.c
index 7607f4598dd8..ae4f9a4b96ac 100644
--- a/kernel/entry/syscall_user_dispatch.c
+++ b/kernel/entry/syscall_user_dispatch.c
@@ -111,3 +111,52 @@ int set_syscall_user_dispatch(unsigned long mode, unsigned long offset,
 
 	return 0;
 }
+
+int syscall_user_dispatch_get_config(struct task_struct *task, unsigned long size,
+		void __user *data)
+{
+	struct syscall_user_dispatch *sd = &task->syscall_dispatch;
+	struct syscall_user_dispatch_config config;
+
+	if (size != sizeof(struct syscall_user_dispatch_config))
+		return -EINVAL;
+
+	if (sd->selector) {
+		config.mode = PR_SYS_DISPATCH_ON;
+		config.offset = sd->offset;
+		config.len = sd->len;
+		config.selector = sd->selector;
+		config.on_dispatch = sd->on_dispatch;
+	} else {
+		config.mode = PR_SYS_DISPATCH_OFF;
+		config.offset = 0;
+		config.len = 0;
+		config.selector = NULL;
+		config.on_dispatch = false;
+	}
+	if (copy_to_user(data, &config, sizeof(config)))
+		return -EFAULT;
+
+	return 0;
+}
+
+int syscall_user_dispatch_set_config(struct task_struct *task, unsigned long size,
+		void __user *data)
+{
+	struct syscall_user_dispatch_config config;
+	int ret;
+
+	if (size != sizeof(struct syscall_user_dispatch_config))
+		return -EINVAL;
+
+	if (copy_from_user(&config, data, sizeof(config)))
+		return -EFAULT;
+
+	ret = set_syscall_user_dispatch(config.mode, config.offset, config.len,
+			config.selector);
+	if (ret)
+		return ret;
+
+	task->syscall_dispatch.on_dispatch = config.on_dispatch;
+	return 0;
+}
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index a6ad815bd4be..0b210a1450e7 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -32,6 +32,7 @@
 #include <linux/compat.h>
 #include <linux/sched/signal.h>
 #include <linux/minmax.h>
+#include <linux/syscall_user_dispatch.h>
 
 #include <asm/syscall.h>	/* for syscall_get_* */
 
@@ -1264,6 +1265,14 @@ int ptrace_request(struct task_struct *child, long request,
 		break;
 #endif
 
+	case PTRACE_SET_SYSCALL_USER_DISPATCH_CONFIG:
+		ret = syscall_user_dispatch_set_config(child, addr, datavp);
+		break;
+
+	case PTRACE_GET_SYSCALL_USER_DISPATCH_CONFIG:
+		ret = syscall_user_dispatch_get_config(child, addr, datavp);
+		break;
+
 	default:
 		break;
 	}
-- 
2.39.0

Re: [PATCH 3/3] ptrace,syscall_user_dispatch: add a getter/setter for sud configuration

[kernel test robot]

Hi Gregory,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v6.2-rc4 next-20230118]
[cannot apply to tip/core/entry]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Gregory-Price/ptrace-syscall_user_dispatch-Implement-Syscall-User-Dispatch-Suspension/20230119-041259
patch link:    https://lore.kernel.org/r/20230118201055.147228-4-gregory.price%40memverge.com
patch subject: [PATCH 3/3] ptrace,syscall_user_dispatch: add a getter/setter for sud configuration
config: m68k-allyesconfig (https://download.01.org/0day-ci/archive/20230119/202301190722.ouyr6mLZ-lkp@intel.com/config)
compiler: m68k-linux-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/bd6833b41ed48c444c09346f695efe229deec2e9
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Gregory-Price/ptrace-syscall_user_dispatch-Implement-Syscall-User-Dispatch-Suspension/20230119-041259
        git checkout bd6833b41ed48c444c09346f695efe229deec2e9
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=m68k olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=m68k prepare

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

   In file included from include/linux/sched.h:31,
                    from arch/m68k/kernel/asm-offsets.c:15:
>> include/linux/syscall_user_dispatch.h:45:5: warning: no previous prototype for 'syscall_user_dispatch_get_config' [-Wmissing-prototypes]
      45 | int syscall_user_dispatch_get_config(struct task_struct *task, unsigned long size,
         |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> include/linux/syscall_user_dispatch.h:51:5: warning: no previous prototype for 'syscall_user_dispatch_set_config' [-Wmissing-prototypes]
      51 | int syscall_user_dispatch_set_config(struct task_struct *task, unsigned long size,
         |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
--
   scripts/genksyms/parse.y: warning: 9 shift/reduce conflicts [-Wconflicts-sr]
   scripts/genksyms/parse.y: warning: 5 reduce/reduce conflicts [-Wconflicts-rr]
   scripts/genksyms/parse.y: note: rerun with option '-Wcounterexamples' to generate conflict counterexamples
   In file included from include/linux/sched.h:31,
                    from arch/m68k/kernel/asm-offsets.c:15:
>> include/linux/syscall_user_dispatch.h:45:5: warning: no previous prototype for 'syscall_user_dispatch_get_config' [-Wmissing-prototypes]
      45 | int syscall_user_dispatch_get_config(struct task_struct *task, unsigned long size,
         |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> include/linux/syscall_user_dispatch.h:51:5: warning: no previous prototype for 'syscall_user_dispatch_set_config' [-Wmissing-prototypes]
      51 | int syscall_user_dispatch_set_config(struct task_struct *task, unsigned long size,
         |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


vim +/syscall_user_dispatch_get_config +45 include/linux/syscall_user_dispatch.h

    44	
  > 45	int syscall_user_dispatch_get_config(struct task_struct *task, unsigned long size,
    46		void __user *data)
    47	{
    48		return -EINVAL;
    49	}
    50	
  > 51	int syscall_user_dispatch_set_config(struct task_struct *task, unsigned long size,
    52		void __user *data)
    53	{
    54		return -EINVAL;
    55	}
    56	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests

Re: [PATCH 3/3] ptrace,syscall_user_dispatch: add a getter/setter for sud configuration

[kernel test robot]

Hi Gregory,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v6.2-rc4 next-20230118]
[cannot apply to tip/core/entry]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Gregory-Price/ptrace-syscall_user_dispatch-Implement-Syscall-User-Dispatch-Suspension/20230119-041259
patch link:    https://lore.kernel.org/r/20230118201055.147228-4-gregory.price%40memverge.com
patch subject: [PATCH 3/3] ptrace,syscall_user_dispatch: add a getter/setter for sud configuration
config: sparc-buildonly-randconfig-r005-20230118 (https://download.01.org/0day-ci/archive/20230119/202301190817.vjgEwo3J-lkp@intel.com/config)
compiler: sparc64-linux-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/bd6833b41ed48c444c09346f695efe229deec2e9
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Gregory-Price/ptrace-syscall_user_dispatch-Implement-Syscall-User-Dispatch-Suspension/20230119-041259
        git checkout bd6833b41ed48c444c09346f695efe229deec2e9
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=sparc olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=sparc SHELL=/bin/bash arch/sparc/mm/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   In file included from include/linux/sched.h:31,
                    from include/linux/mm.h:28,
                    from arch/sparc/mm/tlb.c:9:
>> include/linux/syscall_user_dispatch.h:45:5: error: no previous prototype for 'syscall_user_dispatch_get_config' [-Werror=missing-prototypes]
      45 | int syscall_user_dispatch_get_config(struct task_struct *task, unsigned long size,
         |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> include/linux/syscall_user_dispatch.h:51:5: error: no previous prototype for 'syscall_user_dispatch_set_config' [-Werror=missing-prototypes]
      51 | int syscall_user_dispatch_set_config(struct task_struct *task, unsigned long size,
         |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   cc1: all warnings being treated as errors
--
   In file included from include/linux/sched.h:31,
                    from arch/sparc/mm/init_64.c:11:
>> include/linux/syscall_user_dispatch.h:45:5: error: no previous prototype for 'syscall_user_dispatch_get_config' [-Werror=missing-prototypes]
      45 | int syscall_user_dispatch_get_config(struct task_struct *task, unsigned long size,
         |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> include/linux/syscall_user_dispatch.h:51:5: error: no previous prototype for 'syscall_user_dispatch_set_config' [-Werror=missing-prototypes]
      51 | int syscall_user_dispatch_set_config(struct task_struct *task, unsigned long size,
         |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   arch/sparc/mm/init_64.c: In function 'arch_hugetlb_valid_size':
   arch/sparc/mm/init_64.c:355:24: error: variable 'hv_pgsz_idx' set but not used [-Werror=unused-but-set-variable]
     355 |         unsigned short hv_pgsz_idx;
         |                        ^~~~~~~~~~~
   arch/sparc/mm/init_64.c: At top level:
   arch/sparc/mm/init_64.c:2630:6: error: no previous prototype for 'vmemmap_free' [-Werror=missing-prototypes]
    2630 | void vmemmap_free(unsigned long start, unsigned long end,
         |      ^~~~~~~~~~~~
   cc1: all warnings being treated as errors


vim +/syscall_user_dispatch_get_config +45 include/linux/syscall_user_dispatch.h

    44	
  > 45	int syscall_user_dispatch_get_config(struct task_struct *task, unsigned long size,
    46		void __user *data)
    47	{
    48		return -EINVAL;
    49	}
    50	
  > 51	int syscall_user_dispatch_set_config(struct task_struct *task, unsigned long size,
    52		void __user *data)
    53	{
    54		return -EINVAL;
    55	}
    56	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests

Re: [PATCH 3/3] ptrace,syscall_user_dispatch: add a getter/setter for sud configuration

[kernel test robot]

Hi Gregory,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v6.2-rc4 next-20230118]
[cannot apply to tip/core/entry]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Gregory-Price/ptrace-syscall_user_dispatch-Implement-Syscall-User-Dispatch-Suspension/20230119-041259
patch link:    https://lore.kernel.org/r/20230118201055.147228-4-gregory.price%40memverge.com
patch subject: [PATCH 3/3] ptrace,syscall_user_dispatch: add a getter/setter for sud configuration
config: um-i386_defconfig (https://download.01.org/0day-ci/archive/20230119/202301190907.YBfaBhHB-lkp@intel.com/config)
compiler: gcc-11 (Debian 11.3.0-8) 11.3.0
reproduce (this is a W=1 build):
        # https://github.com/intel-lab-lkp/linux/commit/bd6833b41ed48c444c09346f695efe229deec2e9
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Gregory-Price/ptrace-syscall_user_dispatch-Implement-Syscall-User-Dispatch-Suspension/20230119-041259
        git checkout bd6833b41ed48c444c09346f695efe229deec2e9
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=um SUBARCH=i386 olddefconfig
        make W=1 O=build_dir ARCH=um SUBARCH=i386 SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   ld: fs/isofs/inode.o: in function `syscall_user_dispatch_get_config':
>> include/linux/syscall_user_dispatch.h:49: multiple definition of `syscall_user_dispatch_get_config'; fs/isofs/namei.o:include/linux/syscall_user_dispatch.h:49: first defined here
   ld: fs/isofs/inode.o: in function `syscall_user_dispatch_set_config':
>> include/linux/syscall_user_dispatch.h:49: multiple definition of `syscall_user_dispatch_set_config'; fs/isofs/namei.o:include/linux/syscall_user_dispatch.h:49: first defined here
   ld: fs/isofs/dir.o: in function `syscall_user_dispatch_get_config':
>> include/linux/syscall_user_dispatch.h:49: multiple definition of `syscall_user_dispatch_get_config'; fs/isofs/namei.o:include/linux/syscall_user_dispatch.h:49: first defined here
   ld: fs/isofs/dir.o: in function `syscall_user_dispatch_set_config':
>> include/linux/syscall_user_dispatch.h:49: multiple definition of `syscall_user_dispatch_set_config'; fs/isofs/namei.o:include/linux/syscall_user_dispatch.h:49: first defined here
   ld: fs/isofs/util.o: in function `syscall_user_dispatch_get_config':
   fs/isofs/util.c:49: multiple definition of `syscall_user_dispatch_get_config'; fs/isofs/namei.o:include/linux/syscall_user_dispatch.h:49: first defined here
   ld: fs/isofs/util.o: in function `syscall_user_dispatch_set_config':
   fs/isofs/util.c:49: multiple definition of `syscall_user_dispatch_set_config'; fs/isofs/namei.o:include/linux/syscall_user_dispatch.h:49: first defined here
   ld: fs/isofs/rock.o: in function `syscall_user_dispatch_get_config':
>> include/linux/syscall_user_dispatch.h:49: multiple definition of `syscall_user_dispatch_get_config'; fs/isofs/namei.o:include/linux/syscall_user_dispatch.h:49: first defined here
   ld: fs/isofs/rock.o: in function `syscall_user_dispatch_set_config':
>> include/linux/syscall_user_dispatch.h:49: multiple definition of `syscall_user_dispatch_set_config'; fs/isofs/namei.o:include/linux/syscall_user_dispatch.h:49: first defined here
   ld: fs/isofs/export.o: in function `syscall_user_dispatch_get_config':
>> include/linux/syscall_user_dispatch.h:49: multiple definition of `syscall_user_dispatch_get_config'; fs/isofs/namei.o:include/linux/syscall_user_dispatch.h:49: first defined here
   ld: fs/isofs/export.o: in function `syscall_user_dispatch_set_config':
>> include/linux/syscall_user_dispatch.h:49: multiple definition of `syscall_user_dispatch_set_config'; fs/isofs/namei.o:include/linux/syscall_user_dispatch.h:49: first defined here
   ld: fs/isofs/joliet.o: in function `syscall_user_dispatch_get_config':
   fs/isofs/joliet.c:49: multiple definition of `syscall_user_dispatch_get_config'; fs/isofs/namei.o:include/linux/syscall_user_dispatch.h:49: first defined here
   ld: fs/isofs/joliet.o: in function `syscall_user_dispatch_set_config':
   fs/isofs/joliet.c:49: multiple definition of `syscall_user_dispatch_set_config'; fs/isofs/namei.o:include/linux/syscall_user_dispatch.h:49: first defined here
--
   ld: fs/autofs/inode.o: in function `syscall_user_dispatch_get_config':
>> include/linux/syscall_user_dispatch.h:49: multiple definition of `syscall_user_dispatch_get_config'; fs/autofs/init.o:include/linux/syscall_user_dispatch.h:49: first defined here
   ld: fs/autofs/inode.o: in function `syscall_user_dispatch_set_config':
>> include/linux/syscall_user_dispatch.h:49: multiple definition of `syscall_user_dispatch_set_config'; fs/autofs/init.o:include/linux/syscall_user_dispatch.h:49: first defined here
   ld: fs/autofs/root.o: in function `syscall_user_dispatch_get_config':
>> include/linux/syscall_user_dispatch.h:49: multiple definition of `syscall_user_dispatch_get_config'; fs/autofs/init.o:include/linux/syscall_user_dispatch.h:49: first defined here
   ld: fs/autofs/root.o: in function `syscall_user_dispatch_set_config':
>> include/linux/syscall_user_dispatch.h:49: multiple definition of `syscall_user_dispatch_set_config'; fs/autofs/init.o:include/linux/syscall_user_dispatch.h:49: first defined here
   ld: fs/autofs/symlink.o: in function `syscall_user_dispatch_get_config':
>> include/linux/syscall_user_dispatch.h:49: multiple definition of `syscall_user_dispatch_get_config'; fs/autofs/init.o:include/linux/syscall_user_dispatch.h:49: first defined here
   ld: fs/autofs/symlink.o: in function `syscall_user_dispatch_set_config':
>> include/linux/syscall_user_dispatch.h:49: multiple definition of `syscall_user_dispatch_set_config'; fs/autofs/init.o:include/linux/syscall_user_dispatch.h:49: first defined here
   ld: fs/autofs/waitq.o: in function `syscall_user_dispatch_get_config':
>> include/linux/syscall_user_dispatch.h:49: multiple definition of `syscall_user_dispatch_get_config'; fs/autofs/init.o:include/linux/syscall_user_dispatch.h:49: first defined here
   ld: fs/autofs/waitq.o: in function `syscall_user_dispatch_set_config':
>> include/linux/syscall_user_dispatch.h:49: multiple definition of `syscall_user_dispatch_set_config'; fs/autofs/init.o:include/linux/syscall_user_dispatch.h:49: first defined here
   ld: fs/autofs/expire.o: in function `syscall_user_dispatch_get_config':
>> include/linux/syscall_user_dispatch.h:49: multiple definition of `syscall_user_dispatch_get_config'; fs/autofs/init.o:include/linux/syscall_user_dispatch.h:49: first defined here
   ld: fs/autofs/expire.o: in function `syscall_user_dispatch_set_config':
>> include/linux/syscall_user_dispatch.h:49: multiple definition of `syscall_user_dispatch_set_config'; fs/autofs/init.o:include/linux/syscall_user_dispatch.h:49: first defined here
   ld: fs/autofs/dev-ioctl.o: in function `syscall_user_dispatch_get_config':
>> include/linux/syscall_user_dispatch.h:49: multiple definition of `syscall_user_dispatch_get_config'; fs/autofs/init.o:include/linux/syscall_user_dispatch.h:49: first defined here
   ld: fs/autofs/dev-ioctl.o: in function `syscall_user_dispatch_set_config':
>> include/linux/syscall_user_dispatch.h:49: multiple definition of `syscall_user_dispatch_set_config'; fs/autofs/init.o:include/linux/syscall_user_dispatch.h:49: first defined here


vim +49 include/linux/syscall_user_dispatch.h

    44	
    45	int syscall_user_dispatch_get_config(struct task_struct *task, unsigned long size,
    46		void __user *data)
    47	{
    48		return -EINVAL;
  > 49	}
    50	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests

Re: [PATCH 3/3] ptrace,syscall_user_dispatch: add a getter/setter for sud configuration

[kernel test robot]

Hi Gregory,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v6.2-rc4 next-20230118]
[cannot apply to tip/core/entry]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Gregory-Price/ptrace-syscall_user_dispatch-Implement-Syscall-User-Dispatch-Suspension/20230119-041259
patch link:    https://lore.kernel.org/r/20230118201055.147228-4-gregory.price%40memverge.com
patch subject: [PATCH 3/3] ptrace,syscall_user_dispatch: add a getter/setter for sud configuration
config: x86_64-randconfig-s022 (https://download.01.org/0day-ci/archive/20230119/202301191010.U5yAKr05-lkp@intel.com/config)
compiler: gcc-11 (Debian 11.3.0-8) 11.3.0
reproduce:
        # apt-get install sparse
        # sparse version: v0.6.4-39-gce1a6720-dirty
        # https://github.com/intel-lab-lkp/linux/commit/bd6833b41ed48c444c09346f695efe229deec2e9
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Gregory-Price/ptrace-syscall_user_dispatch-Implement-Syscall-User-Dispatch-Suspension/20230119-041259
        git checkout bd6833b41ed48c444c09346f695efe229deec2e9
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=x86_64 olddefconfig
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=x86_64 SHELL=/bin/bash kernel/entry/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>

sparse warnings: (new ones prefixed by >>)
>> kernel/entry/syscall_user_dispatch.c:128:33: sparse: sparse: incorrect type in assignment (different address spaces) @@     expected signed char [usertype] *[assigned] selector @@     got char [noderef] __user *selector @@
   kernel/entry/syscall_user_dispatch.c:128:33: sparse:     expected signed char [usertype] *[assigned] selector
   kernel/entry/syscall_user_dispatch.c:128:33: sparse:     got char [noderef] __user *selector
>> kernel/entry/syscall_user_dispatch.c:156:31: sparse: sparse: incorrect type in argument 4 (different address spaces) @@     expected char [noderef] __user *selector @@     got signed char [usertype] *[addressable] selector @@
   kernel/entry/syscall_user_dispatch.c:156:31: sparse:     expected char [noderef] __user *selector
   kernel/entry/syscall_user_dispatch.c:156:31: sparse:     got signed char [usertype] *[addressable] selector

vim +128 kernel/entry/syscall_user_dispatch.c

   114	
   115	int syscall_user_dispatch_get_config(struct task_struct *task, unsigned long size,
   116			void __user *data)
   117	{
   118		struct syscall_user_dispatch *sd = &task->syscall_dispatch;
   119		struct syscall_user_dispatch_config config;
   120	
   121		if (size != sizeof(struct syscall_user_dispatch_config))
   122			return -EINVAL;
   123	
   124		if (sd->selector) {
   125			config.mode = PR_SYS_DISPATCH_ON;
   126			config.offset = sd->offset;
   127			config.len = sd->len;
 > 128			config.selector = sd->selector;
   129			config.on_dispatch = sd->on_dispatch;
   130		} else {
   131			config.mode = PR_SYS_DISPATCH_OFF;
   132			config.offset = 0;
   133			config.len = 0;
   134			config.selector = NULL;
   135			config.on_dispatch = false;
   136		}
   137		if (copy_to_user(data, &config, sizeof(config)))
   138			return -EFAULT;
   139	
   140		return 0;
   141	}
   142	
   143	int syscall_user_dispatch_set_config(struct task_struct *task, unsigned long size,
   144			void __user *data)
   145	{
   146		struct syscall_user_dispatch_config config;
   147		int ret;
   148	
   149		if (size != sizeof(struct syscall_user_dispatch_config))
   150			return -EINVAL;
   151	
   152		if (copy_from_user(&config, data, sizeof(config)))
   153			return -EFAULT;
   154	
   155		ret = set_syscall_user_dispatch(config.mode, config.offset, config.len,
 > 156				config.selector);

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests

Re: [PATCH 1/3] ptrace,syscall_user_dispatch: Implement Syscall User Dispatch Suspension

[Peter Zijlstra]

On Wed, Jan 18, 2023 at 03:10:53PM -0500, Gregory Price wrote:
> Adds PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH to ptrace options, and
> modify Syscall User Dispatch to suspend interception when enabled.
> 
> This is modeled after the SUSPEND_SECCOMP feature, which suspends
> SECCOMP interposition.  Without doing this, software like CRIU will
> inject system calls into a process and be intercepted by Syscall
> User Dispatch, either causing a crash (due to blocked signals) or
> the delivery of those signals to a ptracer (not the intended behavior).
> 
> Since Syscall User Dispatch is not a privileged feature, a check
> for permissions is not required, however attempting to set this
> option when CONFIG_CHECKPOINT_RESTORE it not supported should be
> disallowed, as its intended use is checkpoint/resume.
> 
> Signed-off-by: Gregory Price <gregory.price@memverge.com>

One small nit -- see below, otherwise:

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

> ---
>  include/linux/ptrace.h               | 2 ++
>  include/uapi/linux/ptrace.h          | 6 +++++-
>  kernel/entry/syscall_user_dispatch.c | 5 +++++
>  kernel/ptrace.c                      | 5 +++++
>  4 files changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
> index eaaef3ffec22..461ae5c99d57 100644
> --- a/include/linux/ptrace.h
> +++ b/include/linux/ptrace.h
> @@ -45,6 +45,8 @@ extern int ptrace_access_vm(struct task_struct *tsk, unsigned long addr,
>  
>  #define PT_EXITKILL		(PTRACE_O_EXITKILL << PT_OPT_FLAG_SHIFT)
>  #define PT_SUSPEND_SECCOMP	(PTRACE_O_SUSPEND_SECCOMP << PT_OPT_FLAG_SHIFT)
> +#define PT_SUSPEND_SYSCALL_USER_DISPATCH \
> +	(PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH << PT_OPT_FLAG_SHIFT)
>  
>  extern long arch_ptrace(struct task_struct *child, long request,
>  			unsigned long addr, unsigned long data);
> diff --git a/include/uapi/linux/ptrace.h b/include/uapi/linux/ptrace.h
> index 195ae64a8c87..ba9e3f19a22c 100644
> --- a/include/uapi/linux/ptrace.h
> +++ b/include/uapi/linux/ptrace.h
> @@ -146,9 +146,13 @@ struct ptrace_rseq_configuration {
>  /* eventless options */
>  #define PTRACE_O_EXITKILL		(1 << 20)
>  #define PTRACE_O_SUSPEND_SECCOMP	(1 << 21)
> +#define PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH	(1 << 22)
>  
>  #define PTRACE_O_MASK		(\
> -	0x000000ff | PTRACE_O_EXITKILL | PTRACE_O_SUSPEND_SECCOMP)
> +	0x000000ff | \
> +	PTRACE_O_EXITKILL | \
> +	PTRACE_O_SUSPEND_SECCOMP | \
> +	PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH)
>  
>  #include <asm/ptrace.h>
>  
> diff --git a/kernel/entry/syscall_user_dispatch.c b/kernel/entry/syscall_user_dispatch.c
> index 0b6379adff6b..7607f4598dd8 100644
> --- a/kernel/entry/syscall_user_dispatch.c
> +++ b/kernel/entry/syscall_user_dispatch.c
> @@ -8,6 +8,7 @@
>  #include <linux/uaccess.h>
>  #include <linux/signal.h>
>  #include <linux/elf.h>
> +#include <linux/ptrace.h>
>  
>  #include <linux/sched/signal.h>
>  #include <linux/sched/task_stack.h>
> @@ -36,6 +37,10 @@ bool syscall_user_dispatch(struct pt_regs *regs)
>  	struct syscall_user_dispatch *sd = &current->syscall_dispatch;
>  	char state;
>  
> +	if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
> +		unlikely(current->ptrace & PT_SUSPEND_SYSCALL_USER_DISPATCH))

Align with the '(' pleaase.

> +		return false;
> +
>  	if (likely(instruction_pointer(regs) - sd->offset < sd->len))
>  		return false;
>  
> diff --git a/kernel/ptrace.c b/kernel/ptrace.c
> index 54482193e1ed..a6ad815bd4be 100644
> --- a/kernel/ptrace.c
> +++ b/kernel/ptrace.c
> @@ -370,6 +370,11 @@ static int check_ptrace_options(unsigned long data)
>  	if (data & ~(unsigned long)PTRACE_O_MASK)
>  		return -EINVAL;
>  
> +	if (unlikely(data & PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH)) {
> +		if (!IS_ENABLED(CONFIG_CHECKPOINT_RESTART))
> +			return -EINVAL;
> +	}
> +
>  	if (unlikely(data & PTRACE_O_SUSPEND_SECCOMP)) {
>  		if (!IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) ||
>  		    !IS_ENABLED(CONFIG_SECCOMP))
> -- 
> 2.39.0
> 

Re: [PATCH 1/3] ptrace,syscall_user_dispatch: Implement Syscall User Dispatch Suspension

[Damien Le Moal]

On 1/20/23 19:23, Peter Zijlstra wrote:
> On Wed, Jan 18, 2023 at 03:10:53PM -0500, Gregory Price wrote:
>> Adds PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH to ptrace options, and
>> modify Syscall User Dispatch to suspend interception when enabled.
>>
>> This is modeled after the SUSPEND_SECCOMP feature, which suspends
>> SECCOMP interposition.  Without doing this, software like CRIU will
>> inject system calls into a process and be intercepted by Syscall
>> User Dispatch, either causing a crash (due to blocked signals) or
>> the delivery of those signals to a ptracer (not the intended behavior).
>>
>> Since Syscall User Dispatch is not a privileged feature, a check
>> for permissions is not required, however attempting to set this
>> option when CONFIG_CHECKPOINT_RESTORE it not supported should be
>> disallowed, as its intended use is checkpoint/resume.
>>
>> Signed-off-by: Gregory Price <gregory.price@memverge.com>
> 
> One small nit -- see below, otherwise:
> 
> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> 
>> ---
>>  include/linux/ptrace.h               | 2 ++
>>  include/uapi/linux/ptrace.h          | 6 +++++-
>>  kernel/entry/syscall_user_dispatch.c | 5 +++++
>>  kernel/ptrace.c                      | 5 +++++
>>  4 files changed, 17 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
>> index eaaef3ffec22..461ae5c99d57 100644
>> --- a/include/linux/ptrace.h
>> +++ b/include/linux/ptrace.h
>> @@ -45,6 +45,8 @@ extern int ptrace_access_vm(struct task_struct *tsk, unsigned long addr,
>>  
>>  #define PT_EXITKILL		(PTRACE_O_EXITKILL << PT_OPT_FLAG_SHIFT)
>>  #define PT_SUSPEND_SECCOMP	(PTRACE_O_SUSPEND_SECCOMP << PT_OPT_FLAG_SHIFT)
>> +#define PT_SUSPEND_SYSCALL_USER_DISPATCH \
>> +	(PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH << PT_OPT_FLAG_SHIFT)
>>  
>>  extern long arch_ptrace(struct task_struct *child, long request,
>>  			unsigned long addr, unsigned long data);
>> diff --git a/include/uapi/linux/ptrace.h b/include/uapi/linux/ptrace.h
>> index 195ae64a8c87..ba9e3f19a22c 100644
>> --- a/include/uapi/linux/ptrace.h
>> +++ b/include/uapi/linux/ptrace.h
>> @@ -146,9 +146,13 @@ struct ptrace_rseq_configuration {
>>  /* eventless options */
>>  #define PTRACE_O_EXITKILL		(1 << 20)
>>  #define PTRACE_O_SUSPEND_SECCOMP	(1 << 21)
>> +#define PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH	(1 << 22)
>>  
>>  #define PTRACE_O_MASK		(\
>> -	0x000000ff | PTRACE_O_EXITKILL | PTRACE_O_SUSPEND_SECCOMP)
>> +	0x000000ff | \
>> +	PTRACE_O_EXITKILL | \
>> +	PTRACE_O_SUSPEND_SECCOMP | \
>> +	PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH)
>>  
>>  #include <asm/ptrace.h>
>>  
>> diff --git a/kernel/entry/syscall_user_dispatch.c b/kernel/entry/syscall_user_dispatch.c
>> index 0b6379adff6b..7607f4598dd8 100644
>> --- a/kernel/entry/syscall_user_dispatch.c
>> +++ b/kernel/entry/syscall_user_dispatch.c
>> @@ -8,6 +8,7 @@
>>  #include <linux/uaccess.h>
>>  #include <linux/signal.h>
>>  #include <linux/elf.h>
>> +#include <linux/ptrace.h>
>>  
>>  #include <linux/sched/signal.h>
>>  #include <linux/sched/task_stack.h>
>> @@ -36,6 +37,10 @@ bool syscall_user_dispatch(struct pt_regs *regs)
>>  	struct syscall_user_dispatch *sd = &current->syscall_dispatch;
>>  	char state;
>>  
>> +	if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
>> +		unlikely(current->ptrace & PT_SUSPEND_SYSCALL_USER_DISPATCH))
> 
> Align with the '(' pleaase.
> 
>> +		return false;
>> +
>>  	if (likely(instruction_pointer(regs) - sd->offset < sd->len))
>>  		return false;
>>  
>> diff --git a/kernel/ptrace.c b/kernel/ptrace.c
>> index 54482193e1ed..a6ad815bd4be 100644
>> --- a/kernel/ptrace.c
>> +++ b/kernel/ptrace.c
>> @@ -370,6 +370,11 @@ static int check_ptrace_options(unsigned long data)
>>  	if (data & ~(unsigned long)PTRACE_O_MASK)
>>  		return -EINVAL;
>>  
>> +	if (unlikely(data & PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH)) {
>> +		if (!IS_ENABLED(CONFIG_CHECKPOINT_RESTART))

Why not one if with a && ?

>> +			return -EINVAL;
>> +	}
>> +
>>  	if (unlikely(data & PTRACE_O_SUSPEND_SECCOMP)) {
>>  		if (!IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) ||
>>  		    !IS_ENABLED(CONFIG_SECCOMP))
>> -- 
>> 2.39.0
>>

-- 
Damien Le Moal
Western Digital Research

Re: [PATCH 1/3] ptrace,syscall_user_dispatch: Implement Syscall User Dispatch Suspension

[Peter Zijlstra]

On Wed, Jan 18, 2023 at 02:49:31PM -0500, Gregory Price wrote:
> On Wed, Jan 18, 2023 at 02:41:00PM -0500, Gregory Price wrote:
> > ---------- Forwarded message ---------
> > From: Peter Zijlstra <peterz@infradead.org>
> > Date: Wed, Jan 18, 2023 at 12:16 PM
> > Subject: Re: [PATCH 1/3] ptrace,syscall_user_dispatch: Implement Syscall
> > User Dispatch Suspension
> > To: Gregory Price <gourry.memverge@gmail.com>
> > 
> > 
> > On Mon, Jan 09, 2023 at 10:33:46AM -0500, Gregory Price wrote:
> > > @@ -36,6 +37,10 @@ bool syscall_user_dispatch(struct pt_regs *regs)
> > >       struct syscall_user_dispatch *sd = &current->syscall_dispatch;
> > >       char state;
> > >
> > > +     if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
> > > +                     unlikely(current->ptrace &
> > PT_SUSPEND_SYSCALL_USER_DISPATCH))
> > > +             return false;
> > > +
> > >       if (likely(instruction_pointer(regs) - sd->offset < sd->len))
> > >               return false;
> > >
> > 
> > So by making syscall_user_dispatch() return false, we'll make
> > syscall_trace_enter() continue to handle things, and supposedly you want
> > to land in ptrace_report_syscall_entry(), right?
> >
> > ... snip ...
> > 
> > Should setting this then not also depend on having
> > SYSCALL_WORK_SYSCALL_TRACE set? Because without that, you get 'funny'
> > things.
> 
> Hm, this is an interesting question.  My thoughts are that I want the
> process to handle the syscall as-if syscall user dispatch was not
> present at all, regardless of SYSCALL_TRACE.
> 
> This is because some software, like CRIU, actually injects syscalls to
> run in the context of the software in an effort to collect resources.

Oh, right. I used to know that.

> So I actually *want* those 'funny' things to occur, because they're most
> likely intentional.  I don't necessarily want to intercept system calls
> that subsequently occur (although i might).
> 
> So if this feature required SYSCALL_TRACE, you would no longer be able
> to inject system calls ala CRIU.

Yeah, I suppose you're right. It makes it a very sharp instrument, but I
suppose you get what you asked for.

Re: [PATCH 1/3] ptrace,syscall_user_dispatch: Implement Syscall User Dispatch Suspension

[Gregory Price]

On Wed, Jan 18, 2023 at 02:41:00PM -0500, Gregory Price wrote:
> ---------- Forwarded message ---------
> From: Peter Zijlstra <peterz@infradead.org>
> Date: Wed, Jan 18, 2023 at 12:16 PM
> Subject: Re: [PATCH 1/3] ptrace,syscall_user_dispatch: Implement Syscall
> User Dispatch Suspension
> To: Gregory Price <gourry.memverge@gmail.com>
> 
> 
> On Mon, Jan 09, 2023 at 10:33:46AM -0500, Gregory Price wrote:
> > @@ -36,6 +37,10 @@ bool syscall_user_dispatch(struct pt_regs *regs)
> >       struct syscall_user_dispatch *sd = &current->syscall_dispatch;
> >       char state;
> >
> > +     if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
> > +                     unlikely(current->ptrace &
> PT_SUSPEND_SYSCALL_USER_DISPATCH))
> > +             return false;
> > +
> >       if (likely(instruction_pointer(regs) - sd->offset < sd->len))
> >               return false;
> >
> 
> So by making syscall_user_dispatch() return false, we'll make
> syscall_trace_enter() continue to handle things, and supposedly you want
> to land in ptrace_report_syscall_entry(), right?
>
> ... snip ...
> 
> Should setting this then not also depend on having
> SYSCALL_WORK_SYSCALL_TRACE set? Because without that, you get 'funny'
> things.

Hm, this is an interesting question.  My thoughts are that I want the
process to handle the syscall as-if syscall user dispatch was not
present at all, regardless of SYSCALL_TRACE.

This is because some software, like CRIU, actually injects syscalls to
run in the context of the software in an effort to collect resources.

So I actually *want* those 'funny' things to occur, because they're most
likely intentional.  I don't necessarily want to intercept system calls
that subsequently occur (although i might).

So if this feature required SYSCALL_TRACE, you would no longer be able
to inject system calls ala CRIU.

That's also my understanding of the SECCOMP_SUSPEND feature as well,
it's intended specifically to allow *otherwise disallowed* syscalls to
be injected into the process and SECCOMP bypassed. (in this case,
SECCOMP_SUSPEND requires root for exactly this reason).

Re: [PATCH 1/3] ptrace,syscall_user_dispatch: Implement Syscall User Dispatch Suspension

[Peter Zijlstra]

On Mon, Jan 09, 2023 at 10:33:46AM -0500, Gregory Price wrote:
> @@ -36,6 +37,10 @@ bool syscall_user_dispatch(struct pt_regs *regs)
>  	struct syscall_user_dispatch *sd = &current->syscall_dispatch;
>  	char state;
>  
> +	if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
> +			unlikely(current->ptrace & PT_SUSPEND_SYSCALL_USER_DISPATCH))
> +		return false;
> +
>  	if (likely(instruction_pointer(regs) - sd->offset < sd->len))
>  		return false;
>  

So by making syscall_user_dispatch() return false, we'll make
syscall_trace_enter() continue to handle things, and supposedly you want
to land in ptrace_report_syscall_entry(), right?

> diff --git a/kernel/ptrace.c b/kernel/ptrace.c
> index 54482193e1ed..a6ad815bd4be 100644
> --- a/kernel/ptrace.c
> +++ b/kernel/ptrace.c
> @@ -370,6 +370,11 @@ static int check_ptrace_options(unsigned long data)
>  	if (data & ~(unsigned long)PTRACE_O_MASK)
>  		return -EINVAL;
>  
> +	if (unlikely(data & PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH)) {
> +		if (!IS_ENABLED(CONFIG_CHECKPOINT_RESTART))
> +			return -EINVAL;
> +	}

Should setting this then not also depend on having
SYSCALL_WORK_SYSCALL_TRACE set? Because without that, you get 'funny'
things.

[PATCH 1/3] ptrace,syscall_user_dispatch: Implement Syscall User Dispatch Suspension

[Gregory Price]

Adds PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH to ptrace options, and
modify Syscall User Dispatch to suspend interception when enabled.

This is modeled after the SUSPEND_SECCOMP feature, which suspends
SECCOMP interposition.  Without doing this, software like CRIU will
inject system calls into a process and be intercepted by Syscall
User Dispatch, either causing a crash (due to blocked signals) or
the delivery of those signals to a ptracer (not the intended behavior).

Since Syscall User Dispatch is not a privileged feature, a check
for permissions is not required, however attempting to set this
option when CONFIG_CHECKPOINT_RESTORE it not supported should be
disallowed, as its intended use is checkpoint/resume.

Signed-off-by: Gregory Price <gregory.price@memverge.com>
---
 include/linux/ptrace.h               | 2 ++
 include/uapi/linux/ptrace.h          | 6 +++++-
 kernel/entry/syscall_user_dispatch.c | 5 +++++
 kernel/ptrace.c                      | 5 +++++
 4 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index eaaef3ffec22..461ae5c99d57 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -45,6 +45,8 @@ extern int ptrace_access_vm(struct task_struct *tsk, unsigned long addr,
 
 #define PT_EXITKILL		(PTRACE_O_EXITKILL << PT_OPT_FLAG_SHIFT)
 #define PT_SUSPEND_SECCOMP	(PTRACE_O_SUSPEND_SECCOMP << PT_OPT_FLAG_SHIFT)
+#define PT_SUSPEND_SYSCALL_USER_DISPATCH \
+	(PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH << PT_OPT_FLAG_SHIFT)
 
 extern long arch_ptrace(struct task_struct *child, long request,
 			unsigned long addr, unsigned long data);
diff --git a/include/uapi/linux/ptrace.h b/include/uapi/linux/ptrace.h
index 195ae64a8c87..ba9e3f19a22c 100644
--- a/include/uapi/linux/ptrace.h
+++ b/include/uapi/linux/ptrace.h
@@ -146,9 +146,13 @@ struct ptrace_rseq_configuration {
 /* eventless options */
 #define PTRACE_O_EXITKILL		(1 << 20)
 #define PTRACE_O_SUSPEND_SECCOMP	(1 << 21)
+#define PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH	(1 << 22)
 
 #define PTRACE_O_MASK		(\
-	0x000000ff | PTRACE_O_EXITKILL | PTRACE_O_SUSPEND_SECCOMP)
+	0x000000ff | \
+	PTRACE_O_EXITKILL | \
+	PTRACE_O_SUSPEND_SECCOMP | \
+	PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH)
 
 #include <asm/ptrace.h>
 
diff --git a/kernel/entry/syscall_user_dispatch.c b/kernel/entry/syscall_user_dispatch.c
index 0b6379adff6b..f097c06224c9 100644
--- a/kernel/entry/syscall_user_dispatch.c
+++ b/kernel/entry/syscall_user_dispatch.c
@@ -8,6 +8,7 @@
 #include <linux/uaccess.h>
 #include <linux/signal.h>
 #include <linux/elf.h>
+#include <linux/ptrace.h>
 
 #include <linux/sched/signal.h>
 #include <linux/sched/task_stack.h>
@@ -36,6 +37,10 @@ bool syscall_user_dispatch(struct pt_regs *regs)
 	struct syscall_user_dispatch *sd = &current->syscall_dispatch;
 	char state;
 
+	if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
+			unlikely(current->ptrace & PT_SUSPEND_SYSCALL_USER_DISPATCH))
+		return false;
+
 	if (likely(instruction_pointer(regs) - sd->offset < sd->len))
 		return false;
 
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 54482193e1ed..a6ad815bd4be 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -370,6 +370,11 @@ static int check_ptrace_options(unsigned long data)
 	if (data & ~(unsigned long)PTRACE_O_MASK)
 		return -EINVAL;
 
+	if (unlikely(data & PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH)) {
+		if (!IS_ENABLED(CONFIG_CHECKPOINT_RESTART))
+			return -EINVAL;
+	}
+
 	if (unlikely(data & PTRACE_O_SUSPEND_SECCOMP)) {
 		if (!IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) ||
 		    !IS_ENABLED(CONFIG_SECCOMP))
-- 
2.37.3