Re: x86: warning: kernel stack regs has bad 'bp' value

[Andrey Konovalov]

On Wed, May 3, 2017 at 3:30 PM, Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote:
> On Wed, May 03, 2017 at 02:48:28PM +0200, Andrey Konovalov wrote:
>> Hi,
>>
>> I've got the following error report while fuzzing the kernel with syzkaller.
>>
>> On commit 89c9fea3c8034cdb2fd745f551cde0b507fd6893 (4.11.0+).
>>
>> A reproducer and .config are attached.
>>
>> The reproducer open SCTP sockets and sends data to it in a loop.
>> I'm not sure whether this is an issue with SCTP or with something else.
>>
>> WARNING: kernel stack regs at ffff8800686869f8 in a.out:4933 has bad
>> 'bp' value c3fc855a10167ec0
>
> Hi Andrey,
>
> Can you test this patch?

Hi Josh,

This seems to be fixing the reports caused by the reproducers.

I'll keep fuzzing though with syzkaller to make sure.

Thanks!

>
>
> diff --git a/arch/x86/lib/csum-copy_64.S b/arch/x86/lib/csum-copy_64.S
> index 7e48807..45a53df 100644
> --- a/arch/x86/lib/csum-copy_64.S
> +++ b/arch/x86/lib/csum-copy_64.S
> @@ -55,7 +55,7 @@ ENTRY(csum_partial_copy_generic)
>         movq  %r12, 3*8(%rsp)
>         movq  %r14, 4*8(%rsp)
>         movq  %r13, 5*8(%rsp)
> -       movq  %rbp, 6*8(%rsp)
> +       movq  %r15, 6*8(%rsp)
>
>         movq  %r8, (%rsp)
>         movq  %r9, 1*8(%rsp)
> @@ -74,7 +74,7 @@ ENTRY(csum_partial_copy_generic)
>         /* main loop. clear in 64 byte blocks */
>         /* r9: zero, r8: temp2, rbx: temp1, rax: sum, rcx: saved length */
>         /* r11: temp3, rdx: temp4, r12 loopcnt */
> -       /* r10: temp5, rbp: temp6, r14 temp7, r13 temp8 */
> +       /* r10: temp5, r15: temp6, r14 temp7, r13 temp8 */
>         .p2align 4
>  .Lloop:
>         source
> @@ -89,7 +89,7 @@ ENTRY(csum_partial_copy_generic)
>         source
>         movq  32(%rdi), %r10
>         source
> -       movq  40(%rdi), %rbp
> +       movq  40(%rdi), %r15
>         source
>         movq  48(%rdi), %r14
>         source
> @@ -103,7 +103,7 @@ ENTRY(csum_partial_copy_generic)
>         adcq  %r11, %rax
>         adcq  %rdx, %rax
>         adcq  %r10, %rax
> -       adcq  %rbp, %rax
> +       adcq  %r15, %rax
>         adcq  %r14, %rax
>         adcq  %r13, %rax
>
> @@ -121,7 +121,7 @@ ENTRY(csum_partial_copy_generic)
>         dest
>         movq %r10, 32(%rsi)
>         dest
> -       movq %rbp, 40(%rsi)
> +       movq %r15, 40(%rsi)
>         dest
>         movq %r14, 48(%rsi)
>         dest
> @@ -203,7 +203,7 @@ ENTRY(csum_partial_copy_generic)
>         movq 3*8(%rsp), %r12
>         movq 4*8(%rsp), %r14
>         movq 5*8(%rsp), %r13
> -       movq 6*8(%rsp), %rbp
> +       movq 6*8(%rsp), %r15
>         addq $7*8, %rsp
>         ret
>