linux-kernel - Re: BUG: unable to handle kernel paging request in rb

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Message-ID: <20200626164727.GB3565@fieldses.org>
Date:   Fri, 26 Jun 2020 12:47:27 -0400
From:   "J. Bruce Fields" <bfields@...ldses.org>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     Hillf Danton <hdanton@...a.com>,
        syzbot <syzbot+0e37e9d19bded16b8ab9@...kaller.appspotmail.com>,
        chuck.lever@...cle.com, LKML <linux-kernel@...r.kernel.org>,
        linux-nfs@...r.kernel.org,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: BUG: unable to handle kernel paging request in rb_erase

On Fri, Jun 26, 2020 at 12:32:42PM +0200, Dmitry Vyukov wrote:
> So far this crash happened only once:
> https://syzkaller.appspot.com/bug?extid=0e37e9d19bded16b8ab9
> 
> For continuous fuzzing on syzbot it usually means either (1) it's a
> super narrow race or (2) it's a previous unnoticed memory corruption.
> 
> Simpler bugs usually have much higher hit counts:
> https://syzkaller.appspot.com/upstream
> https://syzkaller.appspot.com/upstream/fixed
> 
> If you did a reasonable looking for any obvious bugs in the code that
> would lead to such failure, it can make sense to postpone any
> additional actions until we have more info.
> If no info comes, at some point syzbot will auto-obsolete it, and then
> then we can assume it was (2).

OK, thanks.

It's a big heavily used data structure, if there was random memory
corruption then I guess this wouldn't be a surprising way for it to show
up.

--b.