From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: syzbot <syzbot+ca95b2b7aef9e7cbd6ab@syzkaller.appspotmail.com>,
amir73il@gmail.com, darrick.wong@oracle.com, david@fromorbit.com,
hannes@cmpxchg.org, hughd@google.com, jrdr.linux@gmail.com,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
syzkaller-bugs@googlegroups.com, willy@infradead.org,
Jan Kara <jack@suse.cz>
Subject: Re: BUG: unable to handle kernel NULL pointer dereference in __generic_file_write_iter
Date: Thu, 28 Feb 2019 21:31:29 -0600 [thread overview]
Message-ID: <20190301033129.5tepij2g4lcbvk4s@treble> (raw)
In-Reply-To: <20190221113624.284fe267e73752639186a563@linux-foundation.org>
On Thu, Feb 21, 2019 at 11:36:24AM -0800, Andrew Morton wrote:
> On Thu, 21 Feb 2019 06:52:04 -0800 syzbot <syzbot+ca95b2b7aef9e7cbd6ab@syzkaller.appspotmail.com> wrote:
>
> > Hello,
> >
> > syzbot found the following crash on:
> >
> > HEAD commit: 4aa9fc2a435a Revert "mm, memory_hotplug: initialize struct..
> > git tree: upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=1101382f400000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=4fceea9e2d99ac20
> > dashboard link: https://syzkaller.appspot.com/bug?extid=ca95b2b7aef9e7cbd6ab
> > compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> >
> > Unfortunately, I don't have any reproducer for this crash yet.
>
> Not understanding. That seems to be saying that we got a NULL pointer
> deref in __generic_file_write_iter() at
>
> written = generic_perform_write(file, from, iocb->ki_pos);
>
> which isn't possible.
>
> I'm not seeing recent changes in there which could have caused this. Help.
FWIW, the panic happened in generic_perform_write() when it called
a_ops->write_begin, which was NULL.
I agree with Jann that the unwinders should handle this scenario better.
--
Josh
prev parent reply other threads:[~2019-03-01 3:31 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-21 14:52 BUG: unable to handle kernel NULL pointer dereference in __generic_file_write_iter syzbot
2019-02-21 19:36 ` Andrew Morton
2019-02-27 23:13 ` missing stack trace entry on NULL pointer call [was: Re: BUG: unable to handle kernel NULL pointer dereference in __generic_file_write_iter] Jann Horn
2019-02-28 12:56 ` Thomas Gleixner
2019-02-28 16:34 ` Jann Horn
2019-03-01 0:54 ` Jann Horn
2019-03-01 3:31 ` Josh Poimboeuf [this message]
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