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* [PATCH v10 0/2] arm64: Enable BTI for the executable as well as the interpreter
@ 2022-02-28 13:06 ` Mark Brown
  0 siblings, 0 replies; 16+ messages in thread
From: Mark Brown @ 2022-02-28 13:06 UTC (permalink / raw)
  To: Catalin Marinas, Will Deacon
  Cc: Szabolcs Nagy, Jeremy Linton, H . J . Lu, Yu-cheng Yu, Kees Cook,
	Eric Biederman, linux-arch, linux-arm-kernel, libc-alpha,
	Mark Brown

Deployments of BTI on arm64 have run into issues interacting with
systemd's MemoryDenyWriteExecute feature.  Currently for dynamically
linked executables the kernel will only handle architecture specific
properties like BTI for the interpreter, the expectation is that the
interpreter will then handle any properties on the main executable.
For BTI this means remapping the executable segments PROT_EXEC |
PROT_BTI.

This interacts poorly with MemoryDenyWriteExecute since that is
implemented using a seccomp filter which prevents setting PROT_EXEC on
already mapped memory and lacks the context to be able to detect that
memory is already mapped with PROT_EXEC.  This series resolves this by
providing a sysctl which when enabled will cause the kernel to handle
the BTI property for both the interpreter and the main executable.

v10:
 - Add a sysctl abi.bti_main controlling the new behaviour.
v9:
 - Rebase onto v5.17-rc3.
v8:
 - Rebase onto v5.17-rc1.
v7:
 - Rebase onto v5.16-rc1.
v6:
 - Rebase onto v5.15-rc1.
v5:
 - Rebase onto v5.14-rc2.
 - Tweak changelog on patch 1.
 - Use the helper for interpreter/executable flag in elf.h as well.
v4:
 - Rebase onto v5.14-rc1.
v3:
 - Fix passing of properties for parsing by the main executable.
 - Drop has_interp from arch_parse_elf_property().
 - Coding style tweaks.
v2:
 - Add a patch dropping has_interp from arch_adjust_elf_prot()
 - Fix bisection issue with static executables on arm64 in the first
   patch.

Mark Brown (2):
  elf: Allow architectures to parse properties on the main executable
  arm64: Enable BTI for main executable as well as the interpreter

 arch/arm64/include/asm/elf.h | 14 ++++++++--
 arch/arm64/kernel/process.c  | 52 +++++++++++++++++++++++++++---------
 fs/binfmt_elf.c              | 32 +++++++++++++++-------
 include/linux/elf.h          |  4 ++-
 4 files changed, 77 insertions(+), 25 deletions(-)


base-commit: dfd42facf1e4ada021b939b4e19c935dcdd55566
-- 
2.30.2


^ permalink raw reply	[flat|nested] 16+ messages in thread

* [PATCH v10 0/2] arm64: Enable BTI for the executable as well as the interpreter
@ 2022-02-28 13:06 ` Mark Brown
  0 siblings, 0 replies; 16+ messages in thread
From: Mark Brown @ 2022-02-28 13:06 UTC (permalink / raw)
  To: Catalin Marinas, Will Deacon
  Cc: Szabolcs Nagy, Jeremy Linton, H . J . Lu, Yu-cheng Yu, Kees Cook,
	Eric Biederman, linux-arch, linux-arm-kernel, libc-alpha,
	Mark Brown

Deployments of BTI on arm64 have run into issues interacting with
systemd's MemoryDenyWriteExecute feature.  Currently for dynamically
linked executables the kernel will only handle architecture specific
properties like BTI for the interpreter, the expectation is that the
interpreter will then handle any properties on the main executable.
For BTI this means remapping the executable segments PROT_EXEC |
PROT_BTI.

This interacts poorly with MemoryDenyWriteExecute since that is
implemented using a seccomp filter which prevents setting PROT_EXEC on
already mapped memory and lacks the context to be able to detect that
memory is already mapped with PROT_EXEC.  This series resolves this by
providing a sysctl which when enabled will cause the kernel to handle
the BTI property for both the interpreter and the main executable.

v10:
 - Add a sysctl abi.bti_main controlling the new behaviour.
v9:
 - Rebase onto v5.17-rc3.
v8:
 - Rebase onto v5.17-rc1.
v7:
 - Rebase onto v5.16-rc1.
v6:
 - Rebase onto v5.15-rc1.
v5:
 - Rebase onto v5.14-rc2.
 - Tweak changelog on patch 1.
 - Use the helper for interpreter/executable flag in elf.h as well.
v4:
 - Rebase onto v5.14-rc1.
v3:
 - Fix passing of properties for parsing by the main executable.
 - Drop has_interp from arch_parse_elf_property().
 - Coding style tweaks.
v2:
 - Add a patch dropping has_interp from arch_adjust_elf_prot()
 - Fix bisection issue with static executables on arm64 in the first
   patch.

Mark Brown (2):
  elf: Allow architectures to parse properties on the main executable
  arm64: Enable BTI for main executable as well as the interpreter

 arch/arm64/include/asm/elf.h | 14 ++++++++--
 arch/arm64/kernel/process.c  | 52 +++++++++++++++++++++++++++---------
 fs/binfmt_elf.c              | 32 +++++++++++++++-------
 include/linux/elf.h          |  4 ++-
 4 files changed, 77 insertions(+), 25 deletions(-)


base-commit: dfd42facf1e4ada021b939b4e19c935dcdd55566
-- 
2.30.2


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply	[flat|nested] 16+ messages in thread

* [PATCH v10 1/2] elf: Allow architectures to parse properties on the main executable
  2022-02-28 13:06 ` Mark Brown
@ 2022-02-28 13:06   ` Mark Brown
  -1 siblings, 0 replies; 16+ messages in thread
From: Mark Brown @ 2022-02-28 13:06 UTC (permalink / raw)
  To: Catalin Marinas, Will Deacon
  Cc: Szabolcs Nagy, Jeremy Linton, H . J . Lu, Yu-cheng Yu, Kees Cook,
	Eric Biederman, linux-arch, linux-arm-kernel, libc-alpha,
	Mark Brown, Dave Martin

Currently the ELF code only attempts to parse properties on the image
that will start execution, either the interpreter or for statically linked
executables the main executable. The expectation is that any property
handling for the main executable will be done by the interpreter. This is
a bit inconsistent since we do map the executable and is causing problems
for the arm64 BTI support when used in conjunction with systemd's use of
seccomp to implement MemoryDenyWriteExecute which stops the dynamic linker
adjusting the permissions of executable segments.

Allow architectures to handle properties for both the dynamic linker and
main executable, adjusting arch_parse_elf_properties() to have a new
flag is_interp flag as with arch_elf_adjust_prot() and calling it for
both the main executable and any intepreter.

The user of this code, arm64, is adapted to ensure that there is no
functional change.

Signed-off-by: Mark Brown <broonie@kernel.org>
Tested-by: Jeremy Linton <jeremy.linton@arm.com>
Reviewed-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
---
 arch/arm64/include/asm/elf.h |  3 ++-
 fs/binfmt_elf.c              | 32 +++++++++++++++++++++++---------
 include/linux/elf.h          |  4 +++-
 3 files changed, 28 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
index 97932fbf973d..5cc002376abe 100644
--- a/arch/arm64/include/asm/elf.h
+++ b/arch/arm64/include/asm/elf.h
@@ -259,6 +259,7 @@ struct arch_elf_state {
 
 static inline int arch_parse_elf_property(u32 type, const void *data,
 					  size_t datasz, bool compat,
+					  bool has_interp, bool is_interp,
 					  struct arch_elf_state *arch)
 {
 	/* No known properties for AArch32 yet */
@@ -271,7 +272,7 @@ static inline int arch_parse_elf_property(u32 type, const void *data,
 		if (datasz != sizeof(*p))
 			return -ENOEXEC;
 
-		if (system_supports_bti() &&
+		if (system_supports_bti() && has_interp == is_interp &&
 		    (*p & GNU_PROPERTY_AARCH64_FEATURE_1_BTI))
 			arch->flags |= ARM64_ELF_BTI;
 	}
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 605017eb9349..08b6d992e298 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -716,8 +716,9 @@ static unsigned long load_elf_interp(struct elfhdr *interp_elf_ex,
  */
 
 static int parse_elf_property(const char *data, size_t *off, size_t datasz,
-			      struct arch_elf_state *arch,
-			      bool have_prev_type, u32 *prev_type)
+			      struct arch_elf_state *arch, bool has_interp,
+			      bool is_interp, bool have_prev_type,
+			      u32 *prev_type)
 {
 	size_t o, step;
 	const struct gnu_property *pr;
@@ -751,7 +752,8 @@ static int parse_elf_property(const char *data, size_t *off, size_t datasz,
 	*prev_type = pr->pr_type;
 
 	ret = arch_parse_elf_property(pr->pr_type, data + o,
-				      pr->pr_datasz, ELF_COMPAT, arch);
+				      pr->pr_datasz, ELF_COMPAT,
+				      has_interp, is_interp, arch);
 	if (ret)
 		return ret;
 
@@ -764,6 +766,7 @@ static int parse_elf_property(const char *data, size_t *off, size_t datasz,
 #define NOTE_NAME_SZ (sizeof(GNU_PROPERTY_TYPE_0_NAME))
 
 static int parse_elf_properties(struct file *f, const struct elf_phdr *phdr,
+				bool has_interp, bool is_interp,
 				struct arch_elf_state *arch)
 {
 	union {
@@ -813,7 +816,8 @@ static int parse_elf_properties(struct file *f, const struct elf_phdr *phdr,
 	have_prev_type = false;
 	do {
 		ret = parse_elf_property(note.data, &off, datasz, arch,
-					 have_prev_type, &prev_type);
+					 has_interp, is_interp, have_prev_type,
+					 &prev_type);
 		have_prev_type = true;
 	} while (!ret);
 
@@ -828,6 +832,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
 	unsigned long error;
 	struct elf_phdr *elf_ppnt, *elf_phdata, *interp_elf_phdata = NULL;
 	struct elf_phdr *elf_property_phdata = NULL;
+	struct elf_phdr *interp_elf_property_phdata = NULL;
 	unsigned long elf_bss, elf_brk;
 	int bss_prot = 0;
 	int retval, i;
@@ -865,6 +870,9 @@ static int load_elf_binary(struct linux_binprm *bprm)
 	for (i = 0; i < elf_ex->e_phnum; i++, elf_ppnt++) {
 		char *elf_interpreter;
 
+		if (interpreter && elf_property_phdata)
+			break;
+
 		if (elf_ppnt->p_type == PT_GNU_PROPERTY) {
 			elf_property_phdata = elf_ppnt;
 			continue;
@@ -919,7 +927,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
 		if (retval < 0)
 			goto out_free_dentry;
 
-		break;
+		continue;
 
 out_free_interp:
 		kfree(elf_interpreter);
@@ -963,12 +971,11 @@ static int load_elf_binary(struct linux_binprm *bprm)
 			goto out_free_dentry;
 
 		/* Pass PT_LOPROC..PT_HIPROC headers to arch code */
-		elf_property_phdata = NULL;
 		elf_ppnt = interp_elf_phdata;
 		for (i = 0; i < interp_elf_ex->e_phnum; i++, elf_ppnt++)
 			switch (elf_ppnt->p_type) {
 			case PT_GNU_PROPERTY:
-				elf_property_phdata = elf_ppnt;
+				interp_elf_property_phdata = elf_ppnt;
 				break;
 
 			case PT_LOPROC ... PT_HIPROC:
@@ -979,10 +986,17 @@ static int load_elf_binary(struct linux_binprm *bprm)
 					goto out_free_dentry;
 				break;
 			}
+
+		retval = parse_elf_properties(interpreter,
+					      interp_elf_property_phdata,
+					      true, true, &arch_state);
+		if (retval)
+			goto out_free_dentry;
+
 	}
 
-	retval = parse_elf_properties(interpreter ?: bprm->file,
-				      elf_property_phdata, &arch_state);
+	retval = parse_elf_properties(bprm->file, elf_property_phdata,
+				      interpreter, false, &arch_state);
 	if (retval)
 		goto out_free_dentry;
 
diff --git a/include/linux/elf.h b/include/linux/elf.h
index c9a46c4e183b..1c45ecf29147 100644
--- a/include/linux/elf.h
+++ b/include/linux/elf.h
@@ -88,13 +88,15 @@ struct arch_elf_state;
 #ifndef CONFIG_ARCH_USE_GNU_PROPERTY
 static inline int arch_parse_elf_property(u32 type, const void *data,
 					  size_t datasz, bool compat,
+					  bool has_interp, bool is_interp,
 					  struct arch_elf_state *arch)
 {
 	return 0;
 }
 #else
 extern int arch_parse_elf_property(u32 type, const void *data, size_t datasz,
-				   bool compat, struct arch_elf_state *arch);
+				   bool compat, bool has_interp, bool is_interp,
+				   struct arch_elf_state *arch);
 #endif
 
 #ifdef CONFIG_ARCH_HAVE_ELF_PROT
-- 
2.30.2


^ permalink raw reply related	[flat|nested] 16+ messages in thread

* [PATCH v10 1/2] elf: Allow architectures to parse properties on the main executable
@ 2022-02-28 13:06   ` Mark Brown
  0 siblings, 0 replies; 16+ messages in thread
From: Mark Brown @ 2022-02-28 13:06 UTC (permalink / raw)
  To: Catalin Marinas, Will Deacon
  Cc: Szabolcs Nagy, Jeremy Linton, H . J . Lu, Yu-cheng Yu, Kees Cook,
	Eric Biederman, linux-arch, linux-arm-kernel, libc-alpha,
	Mark Brown, Dave Martin

Currently the ELF code only attempts to parse properties on the image
that will start execution, either the interpreter or for statically linked
executables the main executable. The expectation is that any property
handling for the main executable will be done by the interpreter. This is
a bit inconsistent since we do map the executable and is causing problems
for the arm64 BTI support when used in conjunction with systemd's use of
seccomp to implement MemoryDenyWriteExecute which stops the dynamic linker
adjusting the permissions of executable segments.

Allow architectures to handle properties for both the dynamic linker and
main executable, adjusting arch_parse_elf_properties() to have a new
flag is_interp flag as with arch_elf_adjust_prot() and calling it for
both the main executable and any intepreter.

The user of this code, arm64, is adapted to ensure that there is no
functional change.

Signed-off-by: Mark Brown <broonie@kernel.org>
Tested-by: Jeremy Linton <jeremy.linton@arm.com>
Reviewed-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
---
 arch/arm64/include/asm/elf.h |  3 ++-
 fs/binfmt_elf.c              | 32 +++++++++++++++++++++++---------
 include/linux/elf.h          |  4 +++-
 3 files changed, 28 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
index 97932fbf973d..5cc002376abe 100644
--- a/arch/arm64/include/asm/elf.h
+++ b/arch/arm64/include/asm/elf.h
@@ -259,6 +259,7 @@ struct arch_elf_state {
 
 static inline int arch_parse_elf_property(u32 type, const void *data,
 					  size_t datasz, bool compat,
+					  bool has_interp, bool is_interp,
 					  struct arch_elf_state *arch)
 {
 	/* No known properties for AArch32 yet */
@@ -271,7 +272,7 @@ static inline int arch_parse_elf_property(u32 type, const void *data,
 		if (datasz != sizeof(*p))
 			return -ENOEXEC;
 
-		if (system_supports_bti() &&
+		if (system_supports_bti() && has_interp == is_interp &&
 		    (*p & GNU_PROPERTY_AARCH64_FEATURE_1_BTI))
 			arch->flags |= ARM64_ELF_BTI;
 	}
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 605017eb9349..08b6d992e298 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -716,8 +716,9 @@ static unsigned long load_elf_interp(struct elfhdr *interp_elf_ex,
  */
 
 static int parse_elf_property(const char *data, size_t *off, size_t datasz,
-			      struct arch_elf_state *arch,
-			      bool have_prev_type, u32 *prev_type)
+			      struct arch_elf_state *arch, bool has_interp,
+			      bool is_interp, bool have_prev_type,
+			      u32 *prev_type)
 {
 	size_t o, step;
 	const struct gnu_property *pr;
@@ -751,7 +752,8 @@ static int parse_elf_property(const char *data, size_t *off, size_t datasz,
 	*prev_type = pr->pr_type;
 
 	ret = arch_parse_elf_property(pr->pr_type, data + o,
-				      pr->pr_datasz, ELF_COMPAT, arch);
+				      pr->pr_datasz, ELF_COMPAT,
+				      has_interp, is_interp, arch);
 	if (ret)
 		return ret;
 
@@ -764,6 +766,7 @@ static int parse_elf_property(const char *data, size_t *off, size_t datasz,
 #define NOTE_NAME_SZ (sizeof(GNU_PROPERTY_TYPE_0_NAME))
 
 static int parse_elf_properties(struct file *f, const struct elf_phdr *phdr,
+				bool has_interp, bool is_interp,
 				struct arch_elf_state *arch)
 {
 	union {
@@ -813,7 +816,8 @@ static int parse_elf_properties(struct file *f, const struct elf_phdr *phdr,
 	have_prev_type = false;
 	do {
 		ret = parse_elf_property(note.data, &off, datasz, arch,
-					 have_prev_type, &prev_type);
+					 has_interp, is_interp, have_prev_type,
+					 &prev_type);
 		have_prev_type = true;
 	} while (!ret);
 
@@ -828,6 +832,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
 	unsigned long error;
 	struct elf_phdr *elf_ppnt, *elf_phdata, *interp_elf_phdata = NULL;
 	struct elf_phdr *elf_property_phdata = NULL;
+	struct elf_phdr *interp_elf_property_phdata = NULL;
 	unsigned long elf_bss, elf_brk;
 	int bss_prot = 0;
 	int retval, i;
@@ -865,6 +870,9 @@ static int load_elf_binary(struct linux_binprm *bprm)
 	for (i = 0; i < elf_ex->e_phnum; i++, elf_ppnt++) {
 		char *elf_interpreter;
 
+		if (interpreter && elf_property_phdata)
+			break;
+
 		if (elf_ppnt->p_type == PT_GNU_PROPERTY) {
 			elf_property_phdata = elf_ppnt;
 			continue;
@@ -919,7 +927,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
 		if (retval < 0)
 			goto out_free_dentry;
 
-		break;
+		continue;
 
 out_free_interp:
 		kfree(elf_interpreter);
@@ -963,12 +971,11 @@ static int load_elf_binary(struct linux_binprm *bprm)
 			goto out_free_dentry;
 
 		/* Pass PT_LOPROC..PT_HIPROC headers to arch code */
-		elf_property_phdata = NULL;
 		elf_ppnt = interp_elf_phdata;
 		for (i = 0; i < interp_elf_ex->e_phnum; i++, elf_ppnt++)
 			switch (elf_ppnt->p_type) {
 			case PT_GNU_PROPERTY:
-				elf_property_phdata = elf_ppnt;
+				interp_elf_property_phdata = elf_ppnt;
 				break;
 
 			case PT_LOPROC ... PT_HIPROC:
@@ -979,10 +986,17 @@ static int load_elf_binary(struct linux_binprm *bprm)
 					goto out_free_dentry;
 				break;
 			}
+
+		retval = parse_elf_properties(interpreter,
+					      interp_elf_property_phdata,
+					      true, true, &arch_state);
+		if (retval)
+			goto out_free_dentry;
+
 	}
 
-	retval = parse_elf_properties(interpreter ?: bprm->file,
-				      elf_property_phdata, &arch_state);
+	retval = parse_elf_properties(bprm->file, elf_property_phdata,
+				      interpreter, false, &arch_state);
 	if (retval)
 		goto out_free_dentry;
 
diff --git a/include/linux/elf.h b/include/linux/elf.h
index c9a46c4e183b..1c45ecf29147 100644
--- a/include/linux/elf.h
+++ b/include/linux/elf.h
@@ -88,13 +88,15 @@ struct arch_elf_state;
 #ifndef CONFIG_ARCH_USE_GNU_PROPERTY
 static inline int arch_parse_elf_property(u32 type, const void *data,
 					  size_t datasz, bool compat,
+					  bool has_interp, bool is_interp,
 					  struct arch_elf_state *arch)
 {
 	return 0;
 }
 #else
 extern int arch_parse_elf_property(u32 type, const void *data, size_t datasz,
-				   bool compat, struct arch_elf_state *arch);
+				   bool compat, bool has_interp, bool is_interp,
+				   struct arch_elf_state *arch);
 #endif
 
 #ifdef CONFIG_ARCH_HAVE_ELF_PROT
-- 
2.30.2


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply related	[flat|nested] 16+ messages in thread

* [PATCH v10 2/2] arm64: Enable BTI for main executable as well as the interpreter
  2022-02-28 13:06 ` Mark Brown
@ 2022-02-28 13:06   ` Mark Brown
  -1 siblings, 0 replies; 16+ messages in thread
From: Mark Brown @ 2022-02-28 13:06 UTC (permalink / raw)
  To: Catalin Marinas, Will Deacon
  Cc: Szabolcs Nagy, Jeremy Linton, H . J . Lu, Yu-cheng Yu, Kees Cook,
	Eric Biederman, linux-arch, linux-arm-kernel, libc-alpha,
	Mark Brown

Currently for dynamically linked ELF executables we only enable BTI for
the interpreter, expecting the interpreter to do this for the main
executable. This is a bit inconsistent since we do map main executable and
is causing issues with systemd's MemoryDenyWriteExecute feature which is
implemented using a seccomp filter which prevents setting PROT_EXEC on
already mapped memory and lacks the context to be able to detect that
memory is already mapped with PROT_EXEC.

Resolve this by adding a sysctl abi.bti_main which causes the kernel to
checking the BTI property for the main executable and enable BTI if it
is present when doing the initial mapping. This sysctl is disabled by
default.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
 arch/arm64/include/asm/elf.h | 15 ++++++++---
 arch/arm64/kernel/process.c  | 52 +++++++++++++++++++++++++++---------
 2 files changed, 51 insertions(+), 16 deletions(-)

diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
index 5cc002376abe..c4aa60db76a4 100644
--- a/arch/arm64/include/asm/elf.h
+++ b/arch/arm64/include/asm/elf.h
@@ -251,12 +251,21 @@ struct arch_elf_state {
 	int flags;
 };
 
-#define ARM64_ELF_BTI		(1 << 0)
+#define ARM64_ELF_INTERP_BTI		(1 << 0)
+#define ARM64_ELF_EXEC_BTI		(1 << 1)
 
 #define INIT_ARCH_ELF_STATE {			\
 	.flags = 0,				\
 }
 
+static inline int arm64_elf_bti_flag(bool is_interp)
+{
+	if (is_interp)
+		return ARM64_ELF_INTERP_BTI;
+	else
+		return ARM64_ELF_EXEC_BTI;
+}
+
 static inline int arch_parse_elf_property(u32 type, const void *data,
 					  size_t datasz, bool compat,
 					  bool has_interp, bool is_interp,
@@ -272,9 +281,9 @@ static inline int arch_parse_elf_property(u32 type, const void *data,
 		if (datasz != sizeof(*p))
 			return -ENOEXEC;
 
-		if (system_supports_bti() && has_interp == is_interp &&
+		if (system_supports_bti() &&
 		    (*p & GNU_PROPERTY_AARCH64_FEATURE_1_BTI))
-			arch->flags |= ARM64_ELF_BTI;
+			arch->flags |= arm64_elf_bti_flag(is_interp);
 	}
 
 	return 0;
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 5369e649fa79..82aaf361fa17 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -701,23 +701,49 @@ core_initcall(tagged_addr_init);
 #endif	/* CONFIG_ARM64_TAGGED_ADDR_ABI */
 
 #ifdef CONFIG_BINFMT_ELF
+static unsigned int bti_main;
+
 int arch_elf_adjust_prot(int prot, const struct arch_elf_state *state,
 			 bool has_interp, bool is_interp)
 {
-	/*
-	 * For dynamically linked executables the interpreter is
-	 * responsible for setting PROT_BTI on everything except
-	 * itself.
-	 */
-	if (is_interp != has_interp)
-		return prot;
-
-	if (!(state->flags & ARM64_ELF_BTI))
-		return prot;
-
-	if (prot & PROT_EXEC)
+	if ((prot & PROT_EXEC) &&
+	    (is_interp || !has_interp || bti_main) &&
+	    (state->flags & arm64_elf_bti_flag(is_interp)))
 		prot |= PROT_BTI;
 
 	return prot;
 }
-#endif
+
+#ifdef CONFIG_ARM64_BTI
+/*
+ * If this sysctl is enabled then we will apply PROT_BTI to the main
+ * executable as well as the dynamic linker if it has the appropriate
+ * ELF note.  It is disabled by default, in which case we will only
+ * apply PROT_BTI to the dynamic linker or static binaries.
+ */
+static struct ctl_table bti_main_sysctl_table[] = {
+	{
+		.procname	= "bti_main",
+		.mode		= 0644,
+		.data		= &bti_main,
+		.maxlen		= sizeof(int),
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE,
+	},
+	{ }
+};
+
+static int __init bti_main_init(void)
+{
+	if (!system_supports_bti())
+		return 0;
+
+	if (!register_sysctl("abi", bti_main_sysctl_table))
+		return -EINVAL;
+	return 0;
+}
+core_initcall(bti_main_init);
+#endif /* CONFIG_ARM64_BTI */
+
+#endif /* CONFIG_BINFMT_ELF */
-- 
2.30.2


^ permalink raw reply related	[flat|nested] 16+ messages in thread

* [PATCH v10 2/2] arm64: Enable BTI for main executable as well as the interpreter
@ 2022-02-28 13:06   ` Mark Brown
  0 siblings, 0 replies; 16+ messages in thread
From: Mark Brown @ 2022-02-28 13:06 UTC (permalink / raw)
  To: Catalin Marinas, Will Deacon
  Cc: Szabolcs Nagy, Jeremy Linton, H . J . Lu, Yu-cheng Yu, Kees Cook,
	Eric Biederman, linux-arch, linux-arm-kernel, libc-alpha,
	Mark Brown

Currently for dynamically linked ELF executables we only enable BTI for
the interpreter, expecting the interpreter to do this for the main
executable. This is a bit inconsistent since we do map main executable and
is causing issues with systemd's MemoryDenyWriteExecute feature which is
implemented using a seccomp filter which prevents setting PROT_EXEC on
already mapped memory and lacks the context to be able to detect that
memory is already mapped with PROT_EXEC.

Resolve this by adding a sysctl abi.bti_main which causes the kernel to
checking the BTI property for the main executable and enable BTI if it
is present when doing the initial mapping. This sysctl is disabled by
default.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
 arch/arm64/include/asm/elf.h | 15 ++++++++---
 arch/arm64/kernel/process.c  | 52 +++++++++++++++++++++++++++---------
 2 files changed, 51 insertions(+), 16 deletions(-)

diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
index 5cc002376abe..c4aa60db76a4 100644
--- a/arch/arm64/include/asm/elf.h
+++ b/arch/arm64/include/asm/elf.h
@@ -251,12 +251,21 @@ struct arch_elf_state {
 	int flags;
 };
 
-#define ARM64_ELF_BTI		(1 << 0)
+#define ARM64_ELF_INTERP_BTI		(1 << 0)
+#define ARM64_ELF_EXEC_BTI		(1 << 1)
 
 #define INIT_ARCH_ELF_STATE {			\
 	.flags = 0,				\
 }
 
+static inline int arm64_elf_bti_flag(bool is_interp)
+{
+	if (is_interp)
+		return ARM64_ELF_INTERP_BTI;
+	else
+		return ARM64_ELF_EXEC_BTI;
+}
+
 static inline int arch_parse_elf_property(u32 type, const void *data,
 					  size_t datasz, bool compat,
 					  bool has_interp, bool is_interp,
@@ -272,9 +281,9 @@ static inline int arch_parse_elf_property(u32 type, const void *data,
 		if (datasz != sizeof(*p))
 			return -ENOEXEC;
 
-		if (system_supports_bti() && has_interp == is_interp &&
+		if (system_supports_bti() &&
 		    (*p & GNU_PROPERTY_AARCH64_FEATURE_1_BTI))
-			arch->flags |= ARM64_ELF_BTI;
+			arch->flags |= arm64_elf_bti_flag(is_interp);
 	}
 
 	return 0;
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 5369e649fa79..82aaf361fa17 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -701,23 +701,49 @@ core_initcall(tagged_addr_init);
 #endif	/* CONFIG_ARM64_TAGGED_ADDR_ABI */
 
 #ifdef CONFIG_BINFMT_ELF
+static unsigned int bti_main;
+
 int arch_elf_adjust_prot(int prot, const struct arch_elf_state *state,
 			 bool has_interp, bool is_interp)
 {
-	/*
-	 * For dynamically linked executables the interpreter is
-	 * responsible for setting PROT_BTI on everything except
-	 * itself.
-	 */
-	if (is_interp != has_interp)
-		return prot;
-
-	if (!(state->flags & ARM64_ELF_BTI))
-		return prot;
-
-	if (prot & PROT_EXEC)
+	if ((prot & PROT_EXEC) &&
+	    (is_interp || !has_interp || bti_main) &&
+	    (state->flags & arm64_elf_bti_flag(is_interp)))
 		prot |= PROT_BTI;
 
 	return prot;
 }
-#endif
+
+#ifdef CONFIG_ARM64_BTI
+/*
+ * If this sysctl is enabled then we will apply PROT_BTI to the main
+ * executable as well as the dynamic linker if it has the appropriate
+ * ELF note.  It is disabled by default, in which case we will only
+ * apply PROT_BTI to the dynamic linker or static binaries.
+ */
+static struct ctl_table bti_main_sysctl_table[] = {
+	{
+		.procname	= "bti_main",
+		.mode		= 0644,
+		.data		= &bti_main,
+		.maxlen		= sizeof(int),
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE,
+	},
+	{ }
+};
+
+static int __init bti_main_init(void)
+{
+	if (!system_supports_bti())
+		return 0;
+
+	if (!register_sysctl("abi", bti_main_sysctl_table))
+		return -EINVAL;
+	return 0;
+}
+core_initcall(bti_main_init);
+#endif /* CONFIG_ARM64_BTI */
+
+#endif /* CONFIG_BINFMT_ELF */
-- 
2.30.2


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply related	[flat|nested] 16+ messages in thread

* Re: [PATCH v10 2/2] arm64: Enable BTI for main executable as well as the interpreter
  2022-02-28 13:06   ` Mark Brown
@ 2022-02-28 18:24     ` Catalin Marinas
  -1 siblings, 0 replies; 16+ messages in thread
From: Catalin Marinas @ 2022-02-28 18:24 UTC (permalink / raw)
  To: Mark Brown
  Cc: Will Deacon, Szabolcs Nagy, Jeremy Linton, H . J . Lu,
	Yu-cheng Yu, Kees Cook, Eric Biederman, linux-arch,
	linux-arm-kernel, libc-alpha

On Mon, Feb 28, 2022 at 01:06:06PM +0000, Mark Brown wrote:
> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> index 5369e649fa79..82aaf361fa17 100644
> --- a/arch/arm64/kernel/process.c
> +++ b/arch/arm64/kernel/process.c
> @@ -701,23 +701,49 @@ core_initcall(tagged_addr_init);
>  #endif	/* CONFIG_ARM64_TAGGED_ADDR_ABI */
>  
>  #ifdef CONFIG_BINFMT_ELF
> +static unsigned int bti_main;
> +
>  int arch_elf_adjust_prot(int prot, const struct arch_elf_state *state,
>  			 bool has_interp, bool is_interp)
>  {
> -	/*
> -	 * For dynamically linked executables the interpreter is
> -	 * responsible for setting PROT_BTI on everything except
> -	 * itself.
> -	 */
> -	if (is_interp != has_interp)
> -		return prot;
> -
> -	if (!(state->flags & ARM64_ELF_BTI))
> -		return prot;
> -
> -	if (prot & PROT_EXEC)
> +	if ((prot & PROT_EXEC) &&
> +	    (is_interp || !has_interp || bti_main) &&
> +	    (state->flags & arm64_elf_bti_flag(is_interp)))
>  		prot |= PROT_BTI;
>  
>  	return prot;
>  }

TBH, I liked the other series more as we were getting rid of
'has_interp' in patches 3 and 4. Now we keep it around only for the
bti_main case on dynamic executables (i.e. we need to distinguish them
from static). We could still get rid of has_interp if bti_main was
default on and it affected static binaries as well (for consistency, it
wouldn't be a bad idea).

I think the risk of ABI breaking is negligible in a glibc distro since
currently the dynamic loader sets PROT_BTI on the main exe anyway, just
as the kernel does after this series.

Anyway, from a correctness perspective, this patch looks fine to me,
just a preference for the other series:

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v10 2/2] arm64: Enable BTI for main executable as well as the interpreter
@ 2022-02-28 18:24     ` Catalin Marinas
  0 siblings, 0 replies; 16+ messages in thread
From: Catalin Marinas @ 2022-02-28 18:24 UTC (permalink / raw)
  To: Mark Brown
  Cc: Will Deacon, Szabolcs Nagy, Jeremy Linton, H . J . Lu,
	Yu-cheng Yu, Kees Cook, Eric Biederman, linux-arch,
	linux-arm-kernel, libc-alpha

On Mon, Feb 28, 2022 at 01:06:06PM +0000, Mark Brown wrote:
> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> index 5369e649fa79..82aaf361fa17 100644
> --- a/arch/arm64/kernel/process.c
> +++ b/arch/arm64/kernel/process.c
> @@ -701,23 +701,49 @@ core_initcall(tagged_addr_init);
>  #endif	/* CONFIG_ARM64_TAGGED_ADDR_ABI */
>  
>  #ifdef CONFIG_BINFMT_ELF
> +static unsigned int bti_main;
> +
>  int arch_elf_adjust_prot(int prot, const struct arch_elf_state *state,
>  			 bool has_interp, bool is_interp)
>  {
> -	/*
> -	 * For dynamically linked executables the interpreter is
> -	 * responsible for setting PROT_BTI on everything except
> -	 * itself.
> -	 */
> -	if (is_interp != has_interp)
> -		return prot;
> -
> -	if (!(state->flags & ARM64_ELF_BTI))
> -		return prot;
> -
> -	if (prot & PROT_EXEC)
> +	if ((prot & PROT_EXEC) &&
> +	    (is_interp || !has_interp || bti_main) &&
> +	    (state->flags & arm64_elf_bti_flag(is_interp)))
>  		prot |= PROT_BTI;
>  
>  	return prot;
>  }

TBH, I liked the other series more as we were getting rid of
'has_interp' in patches 3 and 4. Now we keep it around only for the
bti_main case on dynamic executables (i.e. we need to distinguish them
from static). We could still get rid of has_interp if bti_main was
default on and it affected static binaries as well (for consistency, it
wouldn't be a bad idea).

I think the risk of ABI breaking is negligible in a glibc distro since
currently the dynamic loader sets PROT_BTI on the main exe anyway, just
as the kernel does after this series.

Anyway, from a correctness perspective, this patch looks fine to me,
just a preference for the other series:

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v10 0/2] arm64: Enable BTI for the executable as well as the interpreter
  2022-02-28 13:06 ` Mark Brown
@ 2022-03-07 22:03   ` Will Deacon
  -1 siblings, 0 replies; 16+ messages in thread
From: Will Deacon @ 2022-03-07 22:03 UTC (permalink / raw)
  To: Mark Brown, Catalin Marinas
  Cc: kernel-team, Will Deacon, libc-alpha, linux-arch, Yu-cheng Yu,
	H . J . Lu, Jeremy Linton, Eric Biederman, Szabolcs Nagy,
	Kees Cook, linux-arm-kernel

On Mon, 28 Feb 2022 13:06:04 +0000, Mark Brown wrote:
> Deployments of BTI on arm64 have run into issues interacting with
> systemd's MemoryDenyWriteExecute feature.  Currently for dynamically
> linked executables the kernel will only handle architecture specific
> properties like BTI for the interpreter, the expectation is that the
> interpreter will then handle any properties on the main executable.
> For BTI this means remapping the executable segments PROT_EXEC |
> PROT_BTI.
> 
> [...]

Applied to arm64 (for-next/bti), thanks!

[1/2] elf: Allow architectures to parse properties on the main executable
      https://git.kernel.org/arm64/c/825b99a491ec
[2/2] arm64: Enable BTI for main executable as well as the interpreter
      https://git.kernel.org/arm64/c/ddc35eb71d63

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v10 0/2] arm64: Enable BTI for the executable as well as the interpreter
@ 2022-03-07 22:03   ` Will Deacon
  0 siblings, 0 replies; 16+ messages in thread
From: Will Deacon @ 2022-03-07 22:03 UTC (permalink / raw)
  To: Mark Brown, Catalin Marinas
  Cc: kernel-team, Will Deacon, libc-alpha, linux-arch, Yu-cheng Yu,
	H . J . Lu, Jeremy Linton, Eric Biederman, Szabolcs Nagy,
	Kees Cook, linux-arm-kernel

On Mon, 28 Feb 2022 13:06:04 +0000, Mark Brown wrote:
> Deployments of BTI on arm64 have run into issues interacting with
> systemd's MemoryDenyWriteExecute feature.  Currently for dynamically
> linked executables the kernel will only handle architecture specific
> properties like BTI for the interpreter, the expectation is that the
> interpreter will then handle any properties on the main executable.
> For BTI this means remapping the executable segments PROT_EXEC |
> PROT_BTI.
> 
> [...]

Applied to arm64 (for-next/bti), thanks!

[1/2] elf: Allow architectures to parse properties on the main executable
      https://git.kernel.org/arm64/c/825b99a491ec
[2/2] arm64: Enable BTI for main executable as well as the interpreter
      https://git.kernel.org/arm64/c/ddc35eb71d63

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v10 1/2] elf: Allow architectures to parse properties on the main executable
  2022-02-28 13:06   ` Mark Brown
@ 2022-03-08  0:00     ` Kees Cook
  -1 siblings, 0 replies; 16+ messages in thread
From: Kees Cook @ 2022-03-08  0:00 UTC (permalink / raw)
  To: Mark Brown
  Cc: Catalin Marinas, Will Deacon, Szabolcs Nagy, Jeremy Linton,
	H . J . Lu, Yu-cheng Yu, Eric Biederman, linux-arch,
	linux-arm-kernel, libc-alpha, Dave Martin

On Mon, Feb 28, 2022 at 01:06:05PM +0000, Mark Brown wrote:
> Currently the ELF code only attempts to parse properties on the image
> that will start execution, either the interpreter or for statically linked
> executables the main executable. The expectation is that any property
> handling for the main executable will be done by the interpreter. This is
> a bit inconsistent since we do map the executable and is causing problems
> for the arm64 BTI support when used in conjunction with systemd's use of
> seccomp to implement MemoryDenyWriteExecute which stops the dynamic linker
> adjusting the permissions of executable segments.
> 
> Allow architectures to handle properties for both the dynamic linker and
> main executable, adjusting arch_parse_elf_properties() to have a new
> flag is_interp flag as with arch_elf_adjust_prot() and calling it for
> both the main executable and any intepreter.
> 
> The user of this code, arm64, is adapted to ensure that there is no
> functional change.
> 
> Signed-off-by: Mark Brown <broonie@kernel.org>
> Tested-by: Jeremy Linton <jeremy.linton@arm.com>
> Reviewed-by: Dave Martin <Dave.Martin@arm.com>
> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
> ---
>  arch/arm64/include/asm/elf.h |  3 ++-
>  fs/binfmt_elf.c              | 32 +++++++++++++++++++++++---------
>  include/linux/elf.h          |  4 +++-
>  3 files changed, 28 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
> index 97932fbf973d..5cc002376abe 100644
> --- a/arch/arm64/include/asm/elf.h
> +++ b/arch/arm64/include/asm/elf.h
> @@ -259,6 +259,7 @@ struct arch_elf_state {
>  
>  static inline int arch_parse_elf_property(u32 type, const void *data,
>  					  size_t datasz, bool compat,
> +					  bool has_interp, bool is_interp,
>  					  struct arch_elf_state *arch)

Adding more and more args to a functions like this gives me the sense
that some kind of argument structure is needed.

Once I get enough unit testing written in here, I'm hoping to refactor
a bunch of this. To the future! :)

> @@ -828,6 +832,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
>  	unsigned long error;
>  	struct elf_phdr *elf_ppnt, *elf_phdata, *interp_elf_phdata = NULL;
>  	struct elf_phdr *elf_property_phdata = NULL;
> +	struct elf_phdr *interp_elf_property_phdata = NULL;
>  	unsigned long elf_bss, elf_brk;
>  	int bss_prot = 0;
>  	int retval, i;
> @@ -865,6 +870,9 @@ static int load_elf_binary(struct linux_binprm *bprm)
>  	for (i = 0; i < elf_ex->e_phnum; i++, elf_ppnt++) {
>  		char *elf_interpreter;
>  
> +		if (interpreter && elf_property_phdata)
> +			break;
> +

This is not okay. This introduces a memory resource leak for malicious
ELF files with multiple INTERP headers.

>  		if (elf_ppnt->p_type == PT_GNU_PROPERTY) {
>  			elf_property_phdata = elf_ppnt;
>  			continue;
> @@ -919,7 +927,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
>  		if (retval < 0)
>  			goto out_free_dentry;
>  
> -		break;
> +		continue;

Because of this.

As a fix, I'd expect the PT_INTERP test to be updated:

                if (interpreter || elf_ppnt->p_type != PT_INTERP)
                        continue;


>  
>  out_free_interp:
>  		kfree(elf_interpreter);
> @@ -963,12 +971,11 @@ static int load_elf_binary(struct linux_binprm *bprm)
>  			goto out_free_dentry;
>  
>  		/* Pass PT_LOPROC..PT_HIPROC headers to arch code */
> -		elf_property_phdata = NULL;
>  		elf_ppnt = interp_elf_phdata;
>  		for (i = 0; i < interp_elf_ex->e_phnum; i++, elf_ppnt++)
>  			switch (elf_ppnt->p_type) {
>  			case PT_GNU_PROPERTY:
> -				elf_property_phdata = elf_ppnt;
> +				interp_elf_property_phdata = elf_ppnt;
>  				break;
>  
>  			case PT_LOPROC ... PT_HIPROC:
> @@ -979,10 +986,17 @@ static int load_elf_binary(struct linux_binprm *bprm)
>  					goto out_free_dentry;
>  				break;
>  			}
> +
> +		retval = parse_elf_properties(interpreter,
> +					      interp_elf_property_phdata,
> +					      true, true, &arch_state);
> +		if (retval)
> +			goto out_free_dentry;
> +
>  	}
>  
> -	retval = parse_elf_properties(interpreter ?: bprm->file,
> -				      elf_property_phdata, &arch_state);
> +	retval = parse_elf_properties(bprm->file, elf_property_phdata,
> +				      interpreter, false, &arch_state);
>  	if (retval)
>  		goto out_free_dentry;
>  
> diff --git a/include/linux/elf.h b/include/linux/elf.h
> index c9a46c4e183b..1c45ecf29147 100644
> --- a/include/linux/elf.h
> +++ b/include/linux/elf.h
> @@ -88,13 +88,15 @@ struct arch_elf_state;
>  #ifndef CONFIG_ARCH_USE_GNU_PROPERTY
>  static inline int arch_parse_elf_property(u32 type, const void *data,
>  					  size_t datasz, bool compat,
> +					  bool has_interp, bool is_interp,
>  					  struct arch_elf_state *arch)
>  {
>  	return 0;
>  }
>  #else
>  extern int arch_parse_elf_property(u32 type, const void *data, size_t datasz,
> -				   bool compat, struct arch_elf_state *arch);
> +				   bool compat, bool has_interp, bool is_interp,
> +				   struct arch_elf_state *arch);
>  #endif
>  
>  #ifdef CONFIG_ARCH_HAVE_ELF_PROT
> -- 
> 2.30.2
> 

-- 
Kees Cook

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v10 1/2] elf: Allow architectures to parse properties on the main executable
@ 2022-03-08  0:00     ` Kees Cook
  0 siblings, 0 replies; 16+ messages in thread
From: Kees Cook @ 2022-03-08  0:00 UTC (permalink / raw)
  To: Mark Brown
  Cc: Catalin Marinas, Will Deacon, Szabolcs Nagy, Jeremy Linton,
	H . J . Lu, Yu-cheng Yu, Eric Biederman, linux-arch,
	linux-arm-kernel, libc-alpha, Dave Martin

On Mon, Feb 28, 2022 at 01:06:05PM +0000, Mark Brown wrote:
> Currently the ELF code only attempts to parse properties on the image
> that will start execution, either the interpreter or for statically linked
> executables the main executable. The expectation is that any property
> handling for the main executable will be done by the interpreter. This is
> a bit inconsistent since we do map the executable and is causing problems
> for the arm64 BTI support when used in conjunction with systemd's use of
> seccomp to implement MemoryDenyWriteExecute which stops the dynamic linker
> adjusting the permissions of executable segments.
> 
> Allow architectures to handle properties for both the dynamic linker and
> main executable, adjusting arch_parse_elf_properties() to have a new
> flag is_interp flag as with arch_elf_adjust_prot() and calling it for
> both the main executable and any intepreter.
> 
> The user of this code, arm64, is adapted to ensure that there is no
> functional change.
> 
> Signed-off-by: Mark Brown <broonie@kernel.org>
> Tested-by: Jeremy Linton <jeremy.linton@arm.com>
> Reviewed-by: Dave Martin <Dave.Martin@arm.com>
> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
> ---
>  arch/arm64/include/asm/elf.h |  3 ++-
>  fs/binfmt_elf.c              | 32 +++++++++++++++++++++++---------
>  include/linux/elf.h          |  4 +++-
>  3 files changed, 28 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
> index 97932fbf973d..5cc002376abe 100644
> --- a/arch/arm64/include/asm/elf.h
> +++ b/arch/arm64/include/asm/elf.h
> @@ -259,6 +259,7 @@ struct arch_elf_state {
>  
>  static inline int arch_parse_elf_property(u32 type, const void *data,
>  					  size_t datasz, bool compat,
> +					  bool has_interp, bool is_interp,
>  					  struct arch_elf_state *arch)

Adding more and more args to a functions like this gives me the sense
that some kind of argument structure is needed.

Once I get enough unit testing written in here, I'm hoping to refactor
a bunch of this. To the future! :)

> @@ -828,6 +832,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
>  	unsigned long error;
>  	struct elf_phdr *elf_ppnt, *elf_phdata, *interp_elf_phdata = NULL;
>  	struct elf_phdr *elf_property_phdata = NULL;
> +	struct elf_phdr *interp_elf_property_phdata = NULL;
>  	unsigned long elf_bss, elf_brk;
>  	int bss_prot = 0;
>  	int retval, i;
> @@ -865,6 +870,9 @@ static int load_elf_binary(struct linux_binprm *bprm)
>  	for (i = 0; i < elf_ex->e_phnum; i++, elf_ppnt++) {
>  		char *elf_interpreter;
>  
> +		if (interpreter && elf_property_phdata)
> +			break;
> +

This is not okay. This introduces a memory resource leak for malicious
ELF files with multiple INTERP headers.

>  		if (elf_ppnt->p_type == PT_GNU_PROPERTY) {
>  			elf_property_phdata = elf_ppnt;
>  			continue;
> @@ -919,7 +927,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
>  		if (retval < 0)
>  			goto out_free_dentry;
>  
> -		break;
> +		continue;

Because of this.

As a fix, I'd expect the PT_INTERP test to be updated:

                if (interpreter || elf_ppnt->p_type != PT_INTERP)
                        continue;


>  
>  out_free_interp:
>  		kfree(elf_interpreter);
> @@ -963,12 +971,11 @@ static int load_elf_binary(struct linux_binprm *bprm)
>  			goto out_free_dentry;
>  
>  		/* Pass PT_LOPROC..PT_HIPROC headers to arch code */
> -		elf_property_phdata = NULL;
>  		elf_ppnt = interp_elf_phdata;
>  		for (i = 0; i < interp_elf_ex->e_phnum; i++, elf_ppnt++)
>  			switch (elf_ppnt->p_type) {
>  			case PT_GNU_PROPERTY:
> -				elf_property_phdata = elf_ppnt;
> +				interp_elf_property_phdata = elf_ppnt;
>  				break;
>  
>  			case PT_LOPROC ... PT_HIPROC:
> @@ -979,10 +986,17 @@ static int load_elf_binary(struct linux_binprm *bprm)
>  					goto out_free_dentry;
>  				break;
>  			}
> +
> +		retval = parse_elf_properties(interpreter,
> +					      interp_elf_property_phdata,
> +					      true, true, &arch_state);
> +		if (retval)
> +			goto out_free_dentry;
> +
>  	}
>  
> -	retval = parse_elf_properties(interpreter ?: bprm->file,
> -				      elf_property_phdata, &arch_state);
> +	retval = parse_elf_properties(bprm->file, elf_property_phdata,
> +				      interpreter, false, &arch_state);
>  	if (retval)
>  		goto out_free_dentry;
>  
> diff --git a/include/linux/elf.h b/include/linux/elf.h
> index c9a46c4e183b..1c45ecf29147 100644
> --- a/include/linux/elf.h
> +++ b/include/linux/elf.h
> @@ -88,13 +88,15 @@ struct arch_elf_state;
>  #ifndef CONFIG_ARCH_USE_GNU_PROPERTY
>  static inline int arch_parse_elf_property(u32 type, const void *data,
>  					  size_t datasz, bool compat,
> +					  bool has_interp, bool is_interp,
>  					  struct arch_elf_state *arch)
>  {
>  	return 0;
>  }
>  #else
>  extern int arch_parse_elf_property(u32 type, const void *data, size_t datasz,
> -				   bool compat, struct arch_elf_state *arch);
> +				   bool compat, bool has_interp, bool is_interp,
> +				   struct arch_elf_state *arch);
>  #endif
>  
>  #ifdef CONFIG_ARCH_HAVE_ELF_PROT
> -- 
> 2.30.2
> 

-- 
Kees Cook

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v10 1/2] elf: Allow architectures to parse properties on the main executable
  2022-03-08  0:00     ` Kees Cook
@ 2022-03-08  9:45       ` Will Deacon
  -1 siblings, 0 replies; 16+ messages in thread
From: Will Deacon @ 2022-03-08  9:45 UTC (permalink / raw)
  To: Kees Cook
  Cc: Mark Brown, Catalin Marinas, Szabolcs Nagy, Jeremy Linton,
	H . J . Lu, Yu-cheng Yu, Eric Biederman, linux-arch,
	linux-arm-kernel, libc-alpha, Dave Martin

On Mon, Mar 07, 2022 at 04:00:15PM -0800, Kees Cook wrote:
> On Mon, Feb 28, 2022 at 01:06:05PM +0000, Mark Brown wrote:
> > Currently the ELF code only attempts to parse properties on the image
> > that will start execution, either the interpreter or for statically linked
> > executables the main executable. The expectation is that any property
> > handling for the main executable will be done by the interpreter. This is
> > a bit inconsistent since we do map the executable and is causing problems
> > for the arm64 BTI support when used in conjunction with systemd's use of
> > seccomp to implement MemoryDenyWriteExecute which stops the dynamic linker
> > adjusting the permissions of executable segments.
> > 
> > Allow architectures to handle properties for both the dynamic linker and
> > main executable, adjusting arch_parse_elf_properties() to have a new
> > flag is_interp flag as with arch_elf_adjust_prot() and calling it for
> > both the main executable and any intepreter.
> > 
> > The user of this code, arm64, is adapted to ensure that there is no
> > functional change.
> > 
> > Signed-off-by: Mark Brown <broonie@kernel.org>
> > Tested-by: Jeremy Linton <jeremy.linton@arm.com>
> > Reviewed-by: Dave Martin <Dave.Martin@arm.com>
> > Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
> > ---
> >  arch/arm64/include/asm/elf.h |  3 ++-
> >  fs/binfmt_elf.c              | 32 +++++++++++++++++++++++---------
> >  include/linux/elf.h          |  4 +++-
> >  3 files changed, 28 insertions(+), 11 deletions(-)
> > 
> > diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
> > index 97932fbf973d..5cc002376abe 100644
> > --- a/arch/arm64/include/asm/elf.h
> > +++ b/arch/arm64/include/asm/elf.h
> > @@ -259,6 +259,7 @@ struct arch_elf_state {
> >  
> >  static inline int arch_parse_elf_property(u32 type, const void *data,
> >  					  size_t datasz, bool compat,
> > +					  bool has_interp, bool is_interp,
> >  					  struct arch_elf_state *arch)
> 
> Adding more and more args to a functions like this gives me the sense
> that some kind of argument structure is needed.
> 
> Once I get enough unit testing written in here, I'm hoping to refactor
> a bunch of this. To the future! :)
> 
> > @@ -828,6 +832,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
> >  	unsigned long error;
> >  	struct elf_phdr *elf_ppnt, *elf_phdata, *interp_elf_phdata = NULL;
> >  	struct elf_phdr *elf_property_phdata = NULL;
> > +	struct elf_phdr *interp_elf_property_phdata = NULL;
> >  	unsigned long elf_bss, elf_brk;
> >  	int bss_prot = 0;
> >  	int retval, i;
> > @@ -865,6 +870,9 @@ static int load_elf_binary(struct linux_binprm *bprm)
> >  	for (i = 0; i < elf_ex->e_phnum; i++, elf_ppnt++) {
> >  		char *elf_interpreter;
> >  
> > +		if (interpreter && elf_property_phdata)
> > +			break;
> > +
> 
> This is not okay. This introduces a memory resource leak for malicious
> ELF files with multiple INTERP headers.
> 
> >  		if (elf_ppnt->p_type == PT_GNU_PROPERTY) {
> >  			elf_property_phdata = elf_ppnt;
> >  			continue;
> > @@ -919,7 +927,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
> >  		if (retval < 0)
> >  			goto out_free_dentry;
> >  
> > -		break;
> > +		continue;
> 
> Because of this.
> 
> As a fix, I'd expect the PT_INTERP test to be updated:
> 
>                 if (interpreter || elf_ppnt->p_type != PT_INTERP)
>                         continue;

Thanks, Kees. I'll drop this branch from -next until it's been resolved.

Will

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v10 1/2] elf: Allow architectures to parse properties on the main executable
@ 2022-03-08  9:45       ` Will Deacon
  0 siblings, 0 replies; 16+ messages in thread
From: Will Deacon @ 2022-03-08  9:45 UTC (permalink / raw)
  To: Kees Cook
  Cc: Mark Brown, Catalin Marinas, Szabolcs Nagy, Jeremy Linton,
	H . J . Lu, Yu-cheng Yu, Eric Biederman, linux-arch,
	linux-arm-kernel, libc-alpha, Dave Martin

On Mon, Mar 07, 2022 at 04:00:15PM -0800, Kees Cook wrote:
> On Mon, Feb 28, 2022 at 01:06:05PM +0000, Mark Brown wrote:
> > Currently the ELF code only attempts to parse properties on the image
> > that will start execution, either the interpreter or for statically linked
> > executables the main executable. The expectation is that any property
> > handling for the main executable will be done by the interpreter. This is
> > a bit inconsistent since we do map the executable and is causing problems
> > for the arm64 BTI support when used in conjunction with systemd's use of
> > seccomp to implement MemoryDenyWriteExecute which stops the dynamic linker
> > adjusting the permissions of executable segments.
> > 
> > Allow architectures to handle properties for both the dynamic linker and
> > main executable, adjusting arch_parse_elf_properties() to have a new
> > flag is_interp flag as with arch_elf_adjust_prot() and calling it for
> > both the main executable and any intepreter.
> > 
> > The user of this code, arm64, is adapted to ensure that there is no
> > functional change.
> > 
> > Signed-off-by: Mark Brown <broonie@kernel.org>
> > Tested-by: Jeremy Linton <jeremy.linton@arm.com>
> > Reviewed-by: Dave Martin <Dave.Martin@arm.com>
> > Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
> > ---
> >  arch/arm64/include/asm/elf.h |  3 ++-
> >  fs/binfmt_elf.c              | 32 +++++++++++++++++++++++---------
> >  include/linux/elf.h          |  4 +++-
> >  3 files changed, 28 insertions(+), 11 deletions(-)
> > 
> > diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
> > index 97932fbf973d..5cc002376abe 100644
> > --- a/arch/arm64/include/asm/elf.h
> > +++ b/arch/arm64/include/asm/elf.h
> > @@ -259,6 +259,7 @@ struct arch_elf_state {
> >  
> >  static inline int arch_parse_elf_property(u32 type, const void *data,
> >  					  size_t datasz, bool compat,
> > +					  bool has_interp, bool is_interp,
> >  					  struct arch_elf_state *arch)
> 
> Adding more and more args to a functions like this gives me the sense
> that some kind of argument structure is needed.
> 
> Once I get enough unit testing written in here, I'm hoping to refactor
> a bunch of this. To the future! :)
> 
> > @@ -828,6 +832,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
> >  	unsigned long error;
> >  	struct elf_phdr *elf_ppnt, *elf_phdata, *interp_elf_phdata = NULL;
> >  	struct elf_phdr *elf_property_phdata = NULL;
> > +	struct elf_phdr *interp_elf_property_phdata = NULL;
> >  	unsigned long elf_bss, elf_brk;
> >  	int bss_prot = 0;
> >  	int retval, i;
> > @@ -865,6 +870,9 @@ static int load_elf_binary(struct linux_binprm *bprm)
> >  	for (i = 0; i < elf_ex->e_phnum; i++, elf_ppnt++) {
> >  		char *elf_interpreter;
> >  
> > +		if (interpreter && elf_property_phdata)
> > +			break;
> > +
> 
> This is not okay. This introduces a memory resource leak for malicious
> ELF files with multiple INTERP headers.
> 
> >  		if (elf_ppnt->p_type == PT_GNU_PROPERTY) {
> >  			elf_property_phdata = elf_ppnt;
> >  			continue;
> > @@ -919,7 +927,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
> >  		if (retval < 0)
> >  			goto out_free_dentry;
> >  
> > -		break;
> > +		continue;
> 
> Because of this.
> 
> As a fix, I'd expect the PT_INTERP test to be updated:
> 
>                 if (interpreter || elf_ppnt->p_type != PT_INTERP)
>                         continue;

Thanks, Kees. I'll drop this branch from -next until it's been resolved.

Will

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v10 1/2] elf: Allow architectures to parse properties on the main executable
  2022-03-08  0:00     ` Kees Cook
@ 2022-03-08 12:21       ` Mark Brown
  -1 siblings, 0 replies; 16+ messages in thread
From: Mark Brown @ 2022-03-08 12:21 UTC (permalink / raw)
  To: Kees Cook
  Cc: Catalin Marinas, Will Deacon, Szabolcs Nagy, Jeremy Linton,
	H . J . Lu, Yu-cheng Yu, Eric Biederman, linux-arch,
	linux-arm-kernel, libc-alpha, Dave Martin

[-- Attachment #1: Type: text/plain, Size: 742 bytes --]

On Mon, Mar 07, 2022 at 04:00:15PM -0800, Kees Cook wrote:
> On Mon, Feb 28, 2022 at 01:06:05PM +0000, Mark Brown wrote:

> >  static inline int arch_parse_elf_property(u32 type, const void *data,
> >  					  size_t datasz, bool compat,
> > +					  bool has_interp, bool is_interp,
> >  					  struct arch_elf_state *arch)

> Adding more and more args to a functions like this gives me the sense
> that some kind of argument structure is needed.

> Once I get enough unit testing written in here, I'm hoping to refactor
> a bunch of this. To the future! :)

Yes, this code is not lovely.  I'll leave cleanups to future work
though, it seems out of scope here and I'm not sure how good an idea it
is to do too much without more solid testing.

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v10 1/2] elf: Allow architectures to parse properties on the main executable
@ 2022-03-08 12:21       ` Mark Brown
  0 siblings, 0 replies; 16+ messages in thread
From: Mark Brown @ 2022-03-08 12:21 UTC (permalink / raw)
  To: Kees Cook
  Cc: Catalin Marinas, Will Deacon, Szabolcs Nagy, Jeremy Linton,
	H . J . Lu, Yu-cheng Yu, Eric Biederman, linux-arch,
	linux-arm-kernel, libc-alpha, Dave Martin


[-- Attachment #1.1: Type: text/plain, Size: 742 bytes --]

On Mon, Mar 07, 2022 at 04:00:15PM -0800, Kees Cook wrote:
> On Mon, Feb 28, 2022 at 01:06:05PM +0000, Mark Brown wrote:

> >  static inline int arch_parse_elf_property(u32 type, const void *data,
> >  					  size_t datasz, bool compat,
> > +					  bool has_interp, bool is_interp,
> >  					  struct arch_elf_state *arch)

> Adding more and more args to a functions like this gives me the sense
> that some kind of argument structure is needed.

> Once I get enough unit testing written in here, I'm hoping to refactor
> a bunch of this. To the future! :)

Yes, this code is not lovely.  I'll leave cleanups to future work
though, it seems out of scope here and I'm not sure how good an idea it
is to do too much without more solid testing.

[-- Attachment #1.2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

[-- Attachment #2: Type: text/plain, Size: 176 bytes --]

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply	[flat|nested] 16+ messages in thread

end of thread, other threads:[~2022-03-08 12:22 UTC | newest]

Thread overview: 16+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-02-28 13:06 [PATCH v10 0/2] arm64: Enable BTI for the executable as well as the interpreter Mark Brown
2022-02-28 13:06 ` Mark Brown
2022-02-28 13:06 ` [PATCH v10 1/2] elf: Allow architectures to parse properties on the main executable Mark Brown
2022-02-28 13:06   ` Mark Brown
2022-03-08  0:00   ` Kees Cook
2022-03-08  0:00     ` Kees Cook
2022-03-08  9:45     ` Will Deacon
2022-03-08  9:45       ` Will Deacon
2022-03-08 12:21     ` Mark Brown
2022-03-08 12:21       ` Mark Brown
2022-02-28 13:06 ` [PATCH v10 2/2] arm64: Enable BTI for main executable as well as the interpreter Mark Brown
2022-02-28 13:06   ` Mark Brown
2022-02-28 18:24   ` Catalin Marinas
2022-02-28 18:24     ` Catalin Marinas
2022-03-07 22:03 ` [PATCH v10 0/2] arm64: Enable BTI for the " Will Deacon
2022-03-07 22:03   ` Will Deacon

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