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Date: Wed, 11 May 2016 20:51:10 +0300
From: Aaro Koskinen <aaro.koskinen@iki.fi>
To: Khem Raj <raj.khem@gmail.com>, Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org, Kees Cook <keescook@chromium.org>
Subject: Re: [PATCH V2] powerpc/ptrace: Fix out of bounds array access warning
Message-ID: <20160511175110.GC996@raspberrypi.musicnaut.iki.fi>
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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
> 
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