[PATCH 1/2] binfmt: Use struct_size()

[PATCH 1/2] binfmt: Use struct_size()

[Christophe JAILLET]

Use struct_size() instead of hand-writing it. It is less verbose, more
robust and more informative.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
Compile tested on arm
---
 fs/binfmt_elf_fdpic.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index d76ad3d4f676..237ce388d06d 100644
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -748,7 +748,6 @@ static int elf_fdpic_map_file(struct elf_fdpic_params *params,
 	struct elf32_phdr *phdr;
 	unsigned long load_addr, stop;
 	unsigned nloads, tmp;
-	size_t size;
 	int loop, ret;
 
 	/* allocate a load map table */
@@ -760,8 +759,7 @@ static int elf_fdpic_map_file(struct elf_fdpic_params *params,
 	if (nloads == 0)
 		return -ELIBBAD;
 
-	size = sizeof(*loadmap) + nloads * sizeof(*seg);
-	loadmap = kzalloc(size, GFP_KERNEL);
+	loadmap = kzalloc(struct_size(loadmap, segs, nloads), GFP_KERNEL);
 	if (!loadmap)
 		return -ENOMEM;
 
-- 
2.34.1

[PATCH 2/2] binfmt: Slightly simplify elf_fdpic_map_file()

[Christophe JAILLET]

There is no point in initializing 'load_addr' and 'seg' here, they are both
re-written just before being used below.

Doing so, 'load_addr' can be moved in the #ifdef CONFIG_MMU section.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
Compile tested on arm, with and without CONFIG_MMU
---
 fs/binfmt_elf_fdpic.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index 237ce388d06d..1c6c5832af86 100644
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -743,11 +743,12 @@ static int elf_fdpic_map_file(struct elf_fdpic_params *params,
 	struct elf32_fdpic_loadmap *loadmap;
 #ifdef CONFIG_MMU
 	struct elf32_fdpic_loadseg *mseg;
+	unsigned long load_addr;
 #endif
 	struct elf32_fdpic_loadseg *seg;
 	struct elf32_phdr *phdr;
-	unsigned long load_addr, stop;
 	unsigned nloads, tmp;
+	unsigned long stop;
 	int loop, ret;
 
 	/* allocate a load map table */
@@ -768,9 +769,6 @@ static int elf_fdpic_map_file(struct elf_fdpic_params *params,
 	loadmap->version = ELF32_FDPIC_LOADMAP_VERSION;
 	loadmap->nsegs = nloads;
 
-	load_addr = params->load_addr;
-	seg = loadmap->segs;
-
 	/* map the requested LOADs into the memory space */
 	switch (params->flags & ELF_FDPIC_FLAG_ARRANGEMENT) {
 	case ELF_FDPIC_FLAG_CONSTDISP:
-- 
2.34.1

Re: [PATCH 2/2] binfmt: Slightly simplify elf_fdpic_map_file()

[Eric W. Biederman]

Christophe JAILLET <christophe.jaillet@wanadoo.fr> writes:

> There is no point in initializing 'load_addr' and 'seg' here, they are both
> re-written just before being used below.
>
> Doing so, 'load_addr' can be moved in the #ifdef CONFIG_MMU section.
>

Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>

Kees do you maybe want to pick these trivial fixes up?

> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> ---
> Compile tested on arm, with and without CONFIG_MMU
> ---
>  fs/binfmt_elf_fdpic.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
> index 237ce388d06d..1c6c5832af86 100644
> --- a/fs/binfmt_elf_fdpic.c
> +++ b/fs/binfmt_elf_fdpic.c
> @@ -743,11 +743,12 @@ static int elf_fdpic_map_file(struct elf_fdpic_params *params,
>  	struct elf32_fdpic_loadmap *loadmap;
>  #ifdef CONFIG_MMU
>  	struct elf32_fdpic_loadseg *mseg;
> +	unsigned long load_addr;
>  #endif
>  	struct elf32_fdpic_loadseg *seg;
>  	struct elf32_phdr *phdr;
> -	unsigned long load_addr, stop;
>  	unsigned nloads, tmp;
> +	unsigned long stop;
>  	int loop, ret;
>  
>  	/* allocate a load map table */
> @@ -768,9 +769,6 @@ static int elf_fdpic_map_file(struct elf_fdpic_params *params,
>  	loadmap->version = ELF32_FDPIC_LOADMAP_VERSION;
>  	loadmap->nsegs = nloads;
>  
> -	load_addr = params->load_addr;
> -	seg = loadmap->segs;
> -
>  	/* map the requested LOADs into the memory space */
>  	switch (params->flags & ELF_FDPIC_FLAG_ARRANGEMENT) {
>  	case ELF_FDPIC_FLAG_CONSTDISP:

Re: [PATCH 1/2] binfmt: Use struct_size()

[Eric W. Biederman]

Christophe JAILLET <christophe.jaillet@wanadoo.fr> writes:

> Use struct_size() instead of hand-writing it. It is less verbose, more
> robust and more informative.

Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Obviously correct transform.

>
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> ---
> Compile tested on arm
> ---
>  fs/binfmt_elf_fdpic.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
> index d76ad3d4f676..237ce388d06d 100644
> --- a/fs/binfmt_elf_fdpic.c
> +++ b/fs/binfmt_elf_fdpic.c
> @@ -748,7 +748,6 @@ static int elf_fdpic_map_file(struct elf_fdpic_params *params,
>  	struct elf32_phdr *phdr;
>  	unsigned long load_addr, stop;
>  	unsigned nloads, tmp;
> -	size_t size;
>  	int loop, ret;
>  
>  	/* allocate a load map table */
> @@ -760,8 +759,7 @@ static int elf_fdpic_map_file(struct elf_fdpic_params *params,
>  	if (nloads == 0)
>  		return -ELIBBAD;
>  
> -	size = sizeof(*loadmap) + nloads * sizeof(*seg);
> -	loadmap = kzalloc(size, GFP_KERNEL);
> +	loadmap = kzalloc(struct_size(loadmap, segs, nloads), GFP_KERNEL);
>  	if (!loadmap)
>  		return -ENOMEM;

Re: [PATCH 1/2] binfmt: Use struct_size()

[Kees Cook]

On Sun, 28 May 2023 18:20:24 +0200, Christophe JAILLET wrote:
> Use struct_size() instead of hand-writing it. It is less verbose, more
> robust and more informative.
> 
> 

Applied to for-next/execve, thanks!

[1/2] binfmt: Use struct_size()
      https://git.kernel.org/kees/c/e6302d5a285b
[2/2] binfmt: Slightly simplify elf_fdpic_map_file()
      https://git.kernel.org/kees/c/36650a357eac

-- 
Kees Cook