From: Dmitry Vyukov <dvyukov@google.com>
To: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: syzbot <syzbot+ec1b7575afef85a0e5ca@syzkaller.appspotmail.com>,
Andrew Morton <akpm@linux-foundation.org>, Qian Cai <cai@lca.pw>,
David Miller <davem@davemloft.net>,
guro@fb.com, Johannes Weiner <hannes@cmpxchg.org>,
Josef Bacik <jbacik@fb.com>, Kirill Tkhai <ktkhai@virtuozzo.com>,
LKML <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
linux-sctp@vger.kernel.org,
Mel Gorman <mgorman@techsingularity.net>,
Michal Hocko <mhocko@suse.com>, netdev <netdev@vger.kernel.org>,
Neil Horman <nhorman@tuxdriver.com>,
Shakeel Butt <shakeelb@google.com>,
syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Vladislav Yasevich <vyasevich@gmail.com>,
Matthew Wilcox <willy@infradead.org>,
Xin Long <lucien.xin@gmail.com>
Subject: Re: kernel panic: corrupted stack end in wb_workfn
Date: Wed, 20 Mar 2019 10:59:09 +0100 [thread overview]
Message-ID: <CACT4Y+Zj=35t2djhKoq+e1SH3Zu3389Pns7xX6MiMWZ=PFpShA@mail.gmail.com> (raw)
In-Reply-To: <d9e4e36d-1e7a-caaf-f96e-b05592405b5f@virtuozzo.com>
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.
next prev parent reply other threads:[~2019-03-20 9:59 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-31 3:41 syzbot
2018-12-31 3:41 ` syzbot
2018-12-31 3:47 ` Qian Cai
2018-12-31 6:31 ` Dmitry Vyukov
2018-12-31 6:31 ` Dmitry Vyukov
2019-03-17 20:49 ` syzbot
2019-03-19 18:03 ` Xin Long
2019-03-20 9:56 ` Andrey Ryabinin
2019-03-20 9:59 ` Dmitry Vyukov [this message]
2019-03-20 10:23 ` Tetsuo Handa
2019-03-20 10:38 ` Dmitry Vyukov
2019-03-20 10:42 ` Dmitry Vyukov
2019-03-20 10:58 ` Tetsuo Handa
2019-03-20 13:59 ` Dmitry Vyukov
2019-03-20 13:34 ` Andrey Ryabinin
2019-03-20 13:57 ` Dmitry Vyukov
2019-03-21 9:45 ` Dmitry Vyukov
2019-03-21 9:51 ` Dmitry Vyukov
2019-03-21 11:41 ` Tetsuo Handa
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