From: Jens Axboe <firstname.lastname@example.org> To: Jan Kara <email@example.com>, firstname.lastname@example.org Cc: email@example.com, Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>, Tejun Heo <firstname.lastname@example.org> Subject: Re: [PATCH] bdi: Fix oops in wb_workfn() Date: Wed, 9 May 2018 08:42:56 -0600 [thread overview] Message-ID: <email@example.com> (raw) In-Reply-To: <firstname.lastname@example.org> On 5/9/18 4:31 AM, Jan Kara wrote: > On Thu 03-05-18 18:26:26, Jan Kara wrote: >> Syzbot has reported that it can hit a NULL pointer dereference in >> wb_workfn() due to wb->bdi->dev being NULL. This indicates that >> wb_workfn() was called for an already unregistered bdi which should not >> happen as wb_shutdown() called from bdi_unregister() should make sure >> all pending writeback works are completed before bdi is unregistered. >> Except that wb_workfn() itself can requeue the work with: >> >> mod_delayed_work(bdi_wq, &wb->dwork, 0); >> >> and if this happens while wb_shutdown() is waiting in: >> >> flush_delayed_work(&wb->dwork); >> >> the dwork can get executed after wb_shutdown() has finished and >> bdi_unregister() has cleared wb->bdi->dev. >> >> Make wb_workfn() use wakeup_wb() for requeueing the work which takes all >> the necessary precautions against racing with bdi unregistration. >> >> CC: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> >> CC: Tejun Heo <email@example.com> >> Fixes: 839a8e8660b6777e7fe4e80af1a048aebe2b5977 >> Reported-by: syzbot <firstname.lastname@example.org> >> Signed-off-by: Jan Kara <email@example.com> >> --- >> fs/fs-writeback.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) > > Jens, can you please pick up this patch? Probably for the next merge window > (I don't see a reason to rush this at this point in release cycle). Thanks! Looks like I never replied that back, but I did pick it up, and it did in fact go out last week for this series. So we should be all good. I didn't see a need to postpone it, it's obviously correct and fixes a real issue. -- Jens Axboe
prev parent reply other threads:[~2018-05-09 14:42 UTC|newest] Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-05-03 16:26 Jan Kara 2018-05-03 21:55 ` Dave Chinner 2018-05-03 21:57 ` Jens Axboe 2018-05-09 9:48 ` Jan Kara 2018-05-03 22:35 ` Tetsuo Handa 2018-05-09 9:47 ` Jan Kara 2018-05-19 14:27 ` Tetsuo Handa 2018-05-21 9:38 ` Jan Kara 2018-05-25 10:15 ` Tetsuo Handa 2018-05-09 10:31 ` Jan Kara 2018-05-09 14:42 ` Jens Axboe [this message]
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