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From: Dmitry Vyukov <dvyukov@google.com>
To: dsterba@suse.cz, Johannes Thumshirn <jthumshirn@suse.de>,
	Dmitry Vyukov <dvyukov@google.com>,
	Johannes Thumshirn <jth@kernel.org>,
	syzbot <syzbot+5b658d997a83984507a6@syzkaller.appspotmail.com>,
	Chris Mason <clm@fb.com>,
	dsterba@suse.com, linux-btrfs@vger.kernel.org,
	LKML <linux-kernel@vger.kernel.org>,
	syzkaller-bugs <syzkaller-bugs@googlegroups.com>
Subject: Re: kernel BUG at fs/btrfs/volumes.c:LINE!
Date: Thu, 5 Dec 2019 13:06:23 +0100	[thread overview]
Message-ID: <CACT4Y+Z9QezPoc-8nASbK0Bi_ihF=knQ2ngeO8ibdRWbdkEH5g@mail.gmail.com> (raw)
In-Reply-To: <20191205115033.GJ2734@suse.cz>

On Thu, Dec 5, 2019 at 12:50 PM David Sterba <dsterba@suse.cz> wrote:
>
> On Thu, Dec 05, 2019 at 12:38:38PM +0100, Johannes Thumshirn wrote:
> > On Thu, Dec 05, 2019 at 11:07:27AM +0100, Dmitry Vyukov wrote:
> > > The correct syntax would be (no dash + colon):
> > >
> > > #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/jth/linux.git
> > > close_fs_devices
> >
> > Ah ok, thanks.
> >
> > Although syzbot already said it can't test because it has no reproducer.
> > Anyways good to know for future reports.
>
> According to
>
> https://syzkaller.appspot.com/bug?id=d50670eeb21302915bde3f25871dfb7ea43db1e4
>
> there is a way how to test it, many reports and the last one about a
> week old. Is there a way to instruct syzbot to run the same tests on a
> given branch?
>
> (The reproducer is basically setting up environment with limited amount
> of memory available for allocation and this hits the BUG_ON.)

syzkaller does this ("rerun the same tests") for every bug always. If
it succeeds (kernel crashes again), it results in a reproducer, that
can later be used for cause/fix bisection and patch testing. In this
case it does not reproduce, so rerunning the same tests will not lead
to anything useful (only if to false confirmation that a patch fixes
the crash).

There is a large number of reasons why a kernel crash may not
reproduce. It may be global accumulated state, non-hermetic tests,
poor syzkaller btrfs descriptions (most likely true) and others.

Need to take a closer look, on first sight it looks like something
that should be reproduced...

  reply	other threads:[~2019-12-05 12:06 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-06 13:31 syzbot
2018-06-06 16:15 ` Anand Jain
2018-06-07 15:34   ` David Sterba
2018-06-07 16:28     ` Dmitry Vyukov
2018-06-07 16:52       ` David Sterba
2019-06-10 23:14         ` Eric Biggers
2019-06-11 10:01           ` David Sterba
2019-12-04 14:59 ` Johannes Thumshirn
2019-12-05 10:00   ` Johannes Thumshirn
2019-12-05 10:07     ` Dmitry Vyukov
2019-12-05 10:07       ` syzbot
2019-12-05 11:38       ` Johannes Thumshirn
2019-12-05 11:50         ` David Sterba
2019-12-05 12:06           ` Dmitry Vyukov [this message]
2019-12-10 15:11             ` Dmitry Vyukov

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