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

[Julia Cartwright]

From: Khem Raj <raj.khem@xxxxxxxxx>

[ Upstream commit 1e407ee3b21f981140491d5b8a36422979ca246f ]

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@xxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Segher Boessenkool <segher@xxxxxxxxxxxxxxxxxxx>
Tested-by: Aaro Koskinen <aaro.koskinen@xxxxxx>
Acked-by: Olof Johansson <olof@xxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Julia Cartwright <julia@xxxxxx>
---
Hello stable folks-

The following patch introduces no run-time risk, but makes it possible to build
olders in powerpc configurations with newer GCCs.

It's landed upstream as 1e407ee3b21f981140491d5b8a36422979ca246f, and from what
I can tell has been already pulled into 3.12.y, and 4.4.y, but not any of the
other currently maintained stable trees.

Please consider cherry-picking it.

Thanks,
   Julia

 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 f21897b42057..93f200f14e19 100644
--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -376,7 +376,7 @@ 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);
@@ -404,7 +404,7 @@ 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);
-- 
2.12.0