[PATCH V2] powerpc/ptrace: Fix out of bounds array access warning

[PATCH V2] powerpc/ptrace: Fix out of bounds array access warning

[Khem Raj]

gcc-6 correctly warns about a out of bounds access

arch/powerpc/kernel/ptrace.c:407:24: warning: index 32 denotes an offset greater than size of 'u64[32][1] {aka long long unsigned int[32][1]}' [-Warray-bounds]
        offsetof(struct thread_fp_state, fpr[32][0]));
                        ^

check the end of array instead of beginning of next element to fix this

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Segher Boessenkool <segher@kernel.crashing.org>
---
Changes from v1 to v2:
- Check for fpr[32] instead of fpr[31][1]

 arch/powerpc/kernel/ptrace.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
index 30a03c0..060b140 100644
--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -377,7 +377,7 @@ static int fpr_get(struct task_struct *target, const struct user_regset *regset,
 
 #else
 	BUILD_BUG_ON(offsetof(struct thread_fp_state, fpscr) !=
-		     offsetof(struct thread_fp_state, fpr[32][0]));
+		     offsetof(struct thread_fp_state, fpr[32]));
 
 	return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
 				   &target->thread.fp_state, 0, -1);
@@ -405,7 +405,7 @@ static int fpr_set(struct task_struct *target, const struct user_regset *regset,
 	return 0;
 #else
 	BUILD_BUG_ON(offsetof(struct thread_fp_state, fpscr) !=
-		     offsetof(struct thread_fp_state, fpr[32][0]));
+		     offsetof(struct thread_fp_state, fpr[32]));
 
 	return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
 				  &target->thread.fp_state, 0, -1);
-- 
2.8.0

Re: [PATCH V2] powerpc/ptrace: Fix out of bounds array access warning

[Aaro Koskinen]

Hi,

On Mon, Apr 25, 2016 at 09:19:17AM -0700, Khem Raj wrote:
> gcc-6 correctly warns about a out of bounds access
> 
> arch/powerpc/kernel/ptrace.c:407:24: warning: index 32 denotes an offset greater than size of 'u64[32][1] {aka long long unsigned int[32][1]}' [-Warray-bounds]
>         offsetof(struct thread_fp_state, fpr[32][0]));
>                         ^
> 
> check the end of array instead of beginning of next element to fix this
> 
> Signed-off-by: Khem Raj <raj.khem@gmail.com>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Segher Boessenkool <segher@kernel.crashing.org>

This patch fixes PPC kernel build failure with GCC 6.1.

Tested-by: Aaro Koskinen <aaro.koskinen@iki.fi>

Thanks,

A.


> ---
> Changes from v1 to v2:
> - Check for fpr[32] instead of fpr[31][1]
> 
>  arch/powerpc/kernel/ptrace.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
> index 30a03c0..060b140 100644
> --- a/arch/powerpc/kernel/ptrace.c
> +++ b/arch/powerpc/kernel/ptrace.c
> @@ -377,7 +377,7 @@ static int fpr_get(struct task_struct *target, const struct user_regset *regset,
>  
>  #else
>  	BUILD_BUG_ON(offsetof(struct thread_fp_state, fpscr) !=
> -		     offsetof(struct thread_fp_state, fpr[32][0]));
> +		     offsetof(struct thread_fp_state, fpr[32]));
>  
>  	return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
>  				   &target->thread.fp_state, 0, -1);
> @@ -405,7 +405,7 @@ static int fpr_set(struct task_struct *target, const struct user_regset *regset,
>  	return 0;
>  #else
>  	BUILD_BUG_ON(offsetof(struct thread_fp_state, fpscr) !=
> -		     offsetof(struct thread_fp_state, fpr[32][0]));
> +		     offsetof(struct thread_fp_state, fpr[32]));
>  
>  	return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
>  				  &target->thread.fp_state, 0, -1);
> -- 
> 2.8.0
> 
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev@lists.ozlabs.org
> https://lists.ozlabs.org/listinfo/linuxppc-dev

Re: [PATCH V2] powerpc/ptrace: Fix out of bounds array access warning

[Olof Johansson]

On Wed, May 11, 2016 at 10:51 AM, Aaro Koskinen <aaro.koskinen@iki.fi> wrote:
> Hi,
>
> On Mon, Apr 25, 2016 at 09:19:17AM -0700, Khem Raj wrote:
>> gcc-6 correctly warns about a out of bounds access
>>
>> arch/powerpc/kernel/ptrace.c:407:24: warning: index 32 denotes an offset greater than size of 'u64[32][1] {aka long long unsigned int[32][1]}' [-Warray-bounds]
>>         offsetof(struct thread_fp_state, fpr[32][0]));
>>                         ^
>>
>> check the end of array instead of beginning of next element to fix this
>>
>> Signed-off-by: Khem Raj <raj.khem@gmail.com>
>> Cc: Kees Cook <keescook@chromium.org>
>> Cc: Michael Ellerman <mpe@ellerman.id.au>
>> Cc: Segher Boessenkool <segher@kernel.crashing.org>
>
> This patch fixes PPC kernel build failure with GCC 6.1.
>
> Tested-by: Aaro Koskinen <aaro.koskinen@iki.fi>

I question the usefulness of this BUG_BUILD_ON() to be honest, but I'd
like to see _a_ fix go in for it for 4.7-rc3 or so to fix the GCC 6.1
build breakage.

So, consider that an:

Acked-by: Olof Johansson <olof@lixom.net>


-Olof

Re: [V2] powerpc/ptrace: Fix out of bounds array access warning

[Michael Ellerman]

On Mon, 2016-25-04 at 16:19:17 UTC, Khem Raj wrote:
> gcc-6 correctly warns about a out of bounds access
> 
> arch/powerpc/kernel/ptrace.c:407:24: warning: index 32 denotes an offset greater than size of 'u64[32][1] {aka long long unsigned int[32][1]}' [-Warray-bounds]
>         offsetof(struct thread_fp_state, fpr[32][0]));
>                         ^
> 
> check the end of array instead of beginning of next element to fix this
> 
> Signed-off-by: Khem Raj <raj.khem@gmail.com>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Segher Boessenkool <segher@kernel.crashing.org>
> Tested-by: Aaro Koskinen <aaro.koskinen@iki.fi>
> Acked-by: Olof Johansson <olof@lixom.net>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/1e407ee3b21f981140491d5b8a

cheers