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

[Andrey Konovalov]

On Wed, May 3, 2017 at 5:50 PM, Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote:
> 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.

Hi Josh

I didn't see any more reports over the night.

Could you mail the patch?

Thanks!

>
> 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
>>