lkml.org 
[lkml]   [2019]   [Mar]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: kernel panic: corrupted stack end in wb_workfn
On Wed, Mar 20, 2019 at 10:56 AM Andrey Ryabinin
<aryabinin@virtuozzo.com> wrote:
>
> On 3/17/19 11:49 PM, syzbot wrote:
> > syzbot has bisected this bug to:
> >
> > commit c981f254cc82f50f8cb864ce6432097b23195b9c
> > Author: Al Viro <viro@zeniv.linux.org.uk>
> > Date: Sun Jan 7 18:19:09 2018 +0000
> >
> > sctp: use vmemdup_user() rather than badly open-coding memdup_user()
> >
> > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=137bcecf200000
> > start commit: c981f254 sctp: use vmemdup_user() rather than badly open-c..
> > git tree: upstream
> > final crash: https://syzkaller.appspot.com/x/report.txt?x=10fbcecf200000
> > console output: https://syzkaller.appspot.com/x/log.txt?x=177bcecf200000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=5e7dc790609552d7
> > dashboard link: https://syzkaller.appspot.com/bug?extid=ec1b7575afef85a0e5ca
> > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16a9a84b400000
> > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17199bb3400000
> >
> > Reported-by: syzbot+ec1b7575afef85a0e5ca@syzkaller.appspotmail.com
> > Fixes: c981f254 ("sctp: use vmemdup_user() rather than badly open-coding memdup_user()")
>
> From bisection log:
>
> testing release v4.17
> testing commit 29dcea88779c856c7dc92040a0c01233263101d4 with gcc (GCC) 8.1.0
> run #0: crashed: kernel panic: corrupted stack end in wb_workfn
> run #1: crashed: kernel panic: corrupted stack end in worker_thread
> run #2: crashed: kernel panic: Out of memory and no killable processes...
> run #3: crashed: kernel panic: corrupted stack end in wb_workfn
> run #4: crashed: kernel panic: corrupted stack end in wb_workfn
> run #5: crashed: kernel panic: corrupted stack end in wb_workfn
> run #6: crashed: kernel panic: corrupted stack end in wb_workfn
> run #7: crashed: kernel panic: corrupted stack end in wb_workfn
> run #8: crashed: kernel panic: Out of memory and no killable processes...
> run #9: crashed: kernel panic: corrupted stack end in wb_workfn
> testing release v4.16
> testing commit 0adb32858b0bddf4ada5f364a84ed60b196dbcda with gcc (GCC) 8.1.0
> run #0: OK
> run #1: OK
> run #2: OK
> run #3: OK
> run #4: OK
> run #5: crashed: kernel panic: Out of memory and no killable processes...
> run #6: OK
> run #7: crashed: kernel panic: Out of memory and no killable processes...
> run #8: OK
> run #9: OK
> testing release v4.15
> testing commit d8a5b80568a9cb66810e75b182018e9edb68e8ff with gcc (GCC) 8.1.0
> all runs: OK
> # git bisect start v4.16 v4.15
>
> Why bisect started between 4.16 4.15 instead of 4.17 4.16?

Because 4.16 was still crashing and 4.15 was not crashing. 4.15..4.16
looks like the right range, no?


> testing commit c14376de3a1befa70d9811ca2872d47367b48767 with gcc (GCC) 8.1.0
> run #0: crashed: kernel panic: Out of memory and no killable processes...
> run #1: crashed: kernel panic: Out of memory and no killable processes...
> run #2: crashed: kernel panic: Out of memory and no killable processes...
> run #3: crashed: kernel panic: Out of memory and no killable processes...
> run #4: OK
> run #5: OK
> run #6: crashed: WARNING: ODEBUG bug in netdev_freemem
> run #7: crashed: no output from test machine
> run #8: OK
> run #9: OK
> # git bisect bad c14376de3a1befa70d9811ca2872d47367b48767
>
> Why c14376de3a1befa70d9811ca2872d47367b48767 is bad? There was no stack corruption.
> It looks like the syzbot were bisecting a different bug - "kernel panic: Out of memory and no killable processes..."
> And bisection for that bug seems to be correct. kvmalloc() in vmemdup_user() may eat up all memory unlike kmalloc which is limited by KMALLOC_MAX_SIZE (4MB usually).

Please see https://github.com/google/syzkaller/blob/master/docs/syzbot.md#bisection
for answer.

\
 
 \ /
  Last update: 2019-03-20 11:00    [W:0.080 / U:11.192 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site