[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 
Cc: Kees Cook 
Cc: Michael Ellerman 
Cc: Segher Boessenkool 
---
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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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 
> Cc: Kees Cook 
> Cc: Michael Ellerman 
> Cc: Segher Boessenkool 

This patch fixes PPC kernel build failure with GCC 6.1.

Tested-by: Aaro Koskinen 

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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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  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 
>> Cc: Kees Cook 
>> Cc: Michael Ellerman 
>> Cc: Segher Boessenkool 
>
> This patch fixes PPC kernel build failure with GCC 6.1.
>
> Tested-by: Aaro Koskinen 

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
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