diff mbox series

[v4,1/4] elf: Allow architectures to parse properties on the main executable

Message ID 20210712115259.29547-2-broonie@kernel.org
State Not Applicable
Headers show
Series arm64: Enable BTI for the executable as well as the interpreter | expand

Checks

Context Check Description
dj/TryBot-apply_patch fail Patch failed to apply to master at the time it was sent

Commit Message

Mark Brown July 12, 2021, 11:52 a.m. UTC
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 an is_interp
flag as with arch_elf_adjust_prot() and calling it for both the main
executable and any intepreter.

Signed-off-by: Mark Brown <broonie@kernel.org>
Tested-by: Jeremy Linton <jeremy.linton@arm.com>
---
 arch/arm64/include/asm/elf.h |  3 ++-
 fs/binfmt_elf.c              | 31 +++++++++++++++++++++++--------
 include/linux/elf.h          |  4 +++-
 3 files changed, 28 insertions(+), 10 deletions(-)

Comments

Dave Martin July 19, 2021, 10:04 a.m. UTC | #1
On Mon, Jul 12, 2021 at 12:52:56PM +0100, 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 an is_interp

Nit: to have has_interp and is_interp flags

> flag as with arch_elf_adjust_prot() and calling it for both the main
> executable and any intepreter.

It would be helpful to note that the user of this code (arm64) is
adapted to ensure that there is no functional change; otherwise the
arm64 changes look a little non-obvious.

This is not a big deal though, and the code looks fine.

> Signed-off-by: Mark Brown <broonie@kernel.org>
> Tested-by: Jeremy Linton <jeremy.linton@arm.com>

So, with or without the commit message tweaks:

Reviewed-by: Dave Martin <Dave.Martin@arm.com>

> ---
>  arch/arm64/include/asm/elf.h |  3 ++-
>  fs/binfmt_elf.c              | 31 +++++++++++++++++++++++--------
>  include/linux/elf.h          |  4 +++-
>  3 files changed, 28 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
> index 8d1c8dcb87fd..a488a1329b16 100644
> --- a/arch/arm64/include/asm/elf.h
> +++ b/arch/arm64/include/asm/elf.h
> @@ -261,6 +261,7 @@ 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 */
> @@ -273,7 +274,7 @@ 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 439ed81e755a..81e151a57df2 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;
> @@ -936,6 +941,10 @@ static int load_elf_binary(struct linux_binprm *bprm)
>  				executable_stack = EXSTACK_DISABLE_X;
>  			break;
>  
> +		case PT_GNU_PROPERTY:
> +			elf_property_phdata = elf_ppnt;
> +			break;
> +
>  		case PT_LOPROC ... PT_HIPROC:
>  			retval = arch_elf_pt_proc(elf_ex, elf_ppnt,
>  						  bprm->file, false,
> @@ -963,12 +972,11 @@ 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 +987,17 @@ 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 != NULL, 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
> -- 
> 2.20.1
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
diff mbox series

Patch

diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
index 8d1c8dcb87fd..a488a1329b16 100644
--- a/arch/arm64/include/asm/elf.h
+++ b/arch/arm64/include/asm/elf.h
@@ -261,6 +261,7 @@  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 */
@@ -273,7 +274,7 @@  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 439ed81e755a..81e151a57df2 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;
@@ -936,6 +941,10 @@  static int load_elf_binary(struct linux_binprm *bprm)
 				executable_stack = EXSTACK_DISABLE_X;
 			break;
 
+		case PT_GNU_PROPERTY:
+			elf_property_phdata = elf_ppnt;
+			break;
+
 		case PT_LOPROC ... PT_HIPROC:
 			retval = arch_elf_pt_proc(elf_ex, elf_ppnt,
 						  bprm->file, false,
@@ -963,12 +972,11 @@  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 +987,17 @@  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 != NULL, 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