On Sun, Apr 8, 2018 at 8:01 AM, Matthew Wilcox <wi...@infradead.org> wrote: > On Fri, Apr 06, 2018 at 03:33:36PM +0200, Dmitry Vyukov wrote: >> On Fri, Apr 6, 2018 at 3:24 PM, syzbot >> <syzbot+75397ee3df5c70164...@syzkaller.appspotmail.com> wrote: >> > Unfortunately, I don't have any reproducer for this crash yet. >> >> Interesting type of bug, I think we see this for the first time. > > Can you focus syzbot to try to find a reproducer? This seems to be > produced by calling mount() with a pathname that's somewhere between, > say, 3950 & 4100 bytes long from a compat 32-bit task.
Something in the log definitely triggers a very bad heap corruption. This can be reproduced following instructions at: https://github.com/google/syzkaller/blob/master/docs/syzbot.md#syzkaller-reproducers and then running: ./syz-execprog -sandbox=namespace -arch=386 -repeat=0 -procs=10 log.txt where log.txt comes from "Raw console output" link. Note that you need to build syzkaller with 'make TARGETARCH=386' and the use bin/linux_386/syz-executor. While running it I got: BUG: KASAN: double-free or invalid-free in free_request_size+0x5b/0x70 block/blk-core.c:769 https://gist.githubusercontent.com/dvyukov/05f4e77a34795d329aa7a2f40265e396/raw/63a29123b79f1fbad3521d0ff034946be68bfd4a/gistfile1.txt Then kernel BUG at mm/slab.c:4407! https://gist.githubusercontent.com/dvyukov/5b3bcc90d326e9da3636aea2c95ace8f/raw/1589504c708994936681d61ba9d70029998b9b1a/gistfile1.txt And then BUG: unable to handle kernel paging request at ffffebe000000020 https://gist.githubusercontent.com/dvyukov/72025b1c68e488f4fda243e0c152f044/raw/d2c171bc55ad3a43cea33095fa2eea48768b1131/gistfile1.txt One interesting thing is that if I run the log once and it does not crash, then when I try to start binary again I am getting: [ 456.837870] Invalid argument reading file caps for /root/syz-executor The binary somehow becomes broken on disk... I guess syzbot did find a reproducer in this log, but did not attribute it to this bug as it causes crashes all over the place.