On 12 May 2018 at 11:50, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote: > On Sat, May 12, 2018 at 11:09 AM, Ard Biesheuvel > <ard.biesheuvel@xxxxxxxxxx> wrote: >> (+ Arnd) >> >> On 12 May 2018 at 10:43, Dmitry Vyukov <dvyukov@xxxxxxxxxx> 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 >> >> 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 <ard.biesheuvel@xxxxxxxxxx> for any patch that removes the O3 attribute override from keccakf() Thanks, Ard.
