Re: WARNING: kernel stack regs has bad 'bp' value (3)

[Dmitry Vyukov]

On Sat, May 26, 2018 at 9:22 AM, Eric Biggers <ebiggers3@xxxxxxxxx> wrote:
> On Sat, May 12, 2018 at 10:43:08AM +0200, Dmitry Vyukov wrote:
>> On Fri, Feb 2, 2018 at 11:18 PM, Eric Biggers <ebiggers3@xxxxxxxxx> wrote:
>> > On Fri, Feb 02, 2018 at 02:57:32PM +0100, Dmitry Vyukov wrote:
>> >> On Fri, Feb 2, 2018 at 2:48 PM, syzbot
>> >> <syzbot+ffa3a158337bbc01ff09@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>> >> > Hello,
>> >> >
>> >> > syzbot hit the following crash on upstream commit
>> >> > 7109a04eae81c41ed529da9f3c48c3655ccea741 (Thu Feb 1 17:37:30 2018 +0000)
>> >> > Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/ide
>> >> >
>> >> > So far this crash happened 4 times on net-next, upstream.
>> >> > C reproducer is attached.
>> >> > syzkaller reproducer is attached.
>> >> > Raw console output is attached.
>> >> > compiler: gcc (GCC) 7.1.1 20170620
>> >> > .config is attached.
>> >>
>> >>
>> >> From suspicious frames I see salsa20_asm_crypt there, so +crypto maintainers.
>> >>
>> >
>> > Looks like the x86 implementations of Salsa20 (both i586 and x86_64) need to be
>> > updated to not use %ebp/%rbp.
>>
>> Ard,
>>
>> This was bisected as introduced by:
>>
>> commit 83dee2ce1ae791c3dc0c9d4d3a8d42cb109613f6
>> Author: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
>> Date:   Fri Jan 19 12:04:34 2018 +0000
>>
>>     crypto: sha3-generic - rewrite KECCAK transform to help the
>> compiler optimize
>>
>> https://gist.githubusercontent.com/dvyukov/47f93f5a0679170dddf93bc019b42f6d/raw/65beac8ddd30003bbd4e9729236dc8572094abf7/gistfile1.txt
>
> Note that syzbot's original C reproducer (from Feb 1) for this actually
> triggered the warning through salsa20-asm, which I've just proposed to "fix" by
> https://patchwork.kernel.org/patch/10428863/.  sha3-generic is apparently
> another instance of the same bug, where the %rbp register is used for data.


Mailed "crypto: don't optimize keccakf()" to fix this.

Amusingly __optimize("O3") always lead to degraded performance as gcc does not
inline across different optimizations levels, so keccakf() wasn't inlined
into its callers and keccakf_round() wasn't inlined into keccakf().