From: Kees Cook <keescook@chromium.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: Jens Axboe <axboe@kernel.dk>,
syzbot+21cfe1f803e0e158acf1@syzkaller.appspotmail.com,
linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] block: Replace bio_check_ro()'s WARN_ON()
Date: Fri, 22 Nov 2019 11:34:11 -0800 [thread overview]
Message-ID: <201911221131.A34DFAA49@keescook> (raw)
In-Reply-To: <20191122191434.GA10150@infradead.org>
On Fri, Nov 22, 2019 at 11:14:34AM -0800, Christoph Hellwig wrote:
> On Fri, Nov 22, 2019 at 12:09:14PM -0700, Jens Axboe wrote:
> > On 11/22/19 12:07 PM, Christoph Hellwig wrote:
> > > On Fri, Nov 22, 2019 at 10:53:22AM -0800, Kees Cook wrote:
> > >> Friendly ping! I keep tripping over this. Can this please get applied so
> > >> we can silence syzbot and avoid needless WARNs? :)
> > >
> > > What call stack reaches this? Upper layers should never submit a write
> > > bio on a read-only queue, and we need to fix that in the upper layer.
> >
> > It's an fsync, the trace is here:
> >
> > https://syzkaller.appspot.com/x/log.txt?x=159503d2e00000
>
> Oh. I think this is a bug in the block layer, we should not treat
> a sync as write for the purposes of is read-only checks, as it never
> writes data to the device. At the request layer we alread use
> the proper REQ_OP_FLUSH, but at the bio layer we are still abusing
> empty writes apparently. I'll try to cook up something over the
> weekend.
Cool; thanks! Note that syzbot has a reproducer for it:
https://syzkaller.appspot.com/text?tag=ReproC&x=117ccc8c400000
If that doesn't work for your own testing, you can ask syzbot to test
patches itself:
https://goo.gl/tpsmEJ#testing-patches
--
Kees Cook
next prev parent reply other threads:[~2019-11-22 19:34 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-24 21:15 [PATCH] block: Replace bio_check_ro()'s WARN_ON() Kees Cook
2019-11-22 18:53 ` Kees Cook
2019-11-22 18:55 ` Jens Axboe
2019-11-22 18:57 ` Kees Cook
2019-11-22 19:07 ` Christoph Hellwig
2019-11-22 19:09 ` Jens Axboe
2019-11-22 19:14 ` Christoph Hellwig
2019-11-22 19:34 ` Kees Cook [this message]
2019-11-25 17:40 ` Christoph Hellwig
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