On 12 May 2018 at 11:50, Dmitry Vyukov [off-list ref] wrote:

On Sat, May 12, 2018 at 11:09 AM, Ard Biesheuvel
[off-list ref] wrote:

quoted

(+ Arnd)

On 12 May 2018 at 10:43, Dmitry Vyukov [off-list ref] wrote:

quoted

On Fri, Feb 2, 2018 at 11:18 PM, Eric Biggers [off-list ref] wrote:

quoted

On Fri, Feb 02, 2018 at 02:57:32PM +0100, Dmitry Vyukov wrote:

quoted

On Fri, Feb 2, 2018 at 2:48 PM, syzbot
[off-list ref] wrote:

quoted

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 [off-list ref]
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

Ouch.

I'm not an expert in x86 assembly. Could someone please check the
generated code to see what's going on? The C code changes are not that
intricate, they basically unroll a loop, replacing accesses to
'array[indirect_index[i]]' with 'array[constant]'.

As mentioned in the commit log, the speedup is more than significant
for architectures with lots of GPRs so I'd prefer fixing the patch
over reverting it (if there is anything wrong with the code in the
first place)

I suspect the problem is with __attribute__((__optimize__("O3"))). It
makes compiler use rbp register, which must not be used.

IIRC, the additional speedup from adding that was significant but not
huge. Given that we don't use O3 anywhere else, I guess we should just
remove it.

Could you please check whether that makes the issue go away?

If so,

Acked-by: Ard Biesheuvel <redacted>

for any patch that removes the O3 attribute override from keccakf()

Thanks,
Ard.