linux-kernel - Re: kernel BUG in ext4_free

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Date:   Fri, 16 Dec 2022 14:12:49 +0000
From:   Lee Jones <lee@...nel.org>
To:     Aleksandr Nogikh <nogikh@...gle.com>
Cc:     Theodore Ts'o <tytso@....edu>,
        syzbot <syzbot+15cd994e273307bf5cfa@...kaller.appspotmail.com>,
        adilger.kernel@...ger.ca, gregkh@...uxfoundation.org,
        lczerner@...hat.com, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org, sashal@...nel.org,
        stable@...r.kernel.org, syzkaller-android-bugs@...glegroups.com,
        tadeusz.struk@...aro.org
Subject: Re: kernel BUG in ext4_free_blocks (2)

On Fri, 16 Dec 2022, Aleksandr Nogikh wrote:

> On Fri, Dec 16, 2022 at 2:01 PM Lee Jones <lee@...nel.org> wrote:
> >
> > On Thu, 15 Dec 2022, Theodore Ts'o wrote:
> >
> > > On Thu, Dec 15, 2022 at 08:34:35AM -0800, syzbot wrote:
> > > > This bug is marked as fixed by commit:
> > > > ext4: block range must be validated before use in ext4_mb_clear_bb()
> > > > But I can't find it in any tested tree for more than 90 days.
> > > > Is it a correct commit? Please update it by replying:
> > > > #syz fix: exact-commit-title
> > > > Until then the bug is still considered open and
> > > > new crashes with the same signature are ignored.
> > >
> > > I don't know what is going on with syzkaller's commit detection, but
> > > commit 1e1c2b86ef86 ("ext4: block range must be validated before use
> > > in ext4_mb_clear_bb()") is an exact match for the commit title, and
> > > it's been in the upstream kernel since v6.0.
> > >
> > > How do we make syzkaller accept this?  I'll try this again, but I
> > > don't hold out much hope.
> >
> > I don't see the original bug report (was it posted to a lore
> > associated list?), so there is no way to tell what branch syzbot was
> > fuzzing at the time.  My assumption is that it was !Mainline.
> 
> Syzbot is actually reacting here to this bug from the Android namespace:
> 
> https://syzkaller.appspot.com/bug?id=5266d464285a03cee9dbfda7d2452a72c3c2ae7c
> 
> > Although this does appear to be a Stable candidate, I do not see it
> > in any of the Stable branches yet.  So I suspect the answer here is to
> > wait for the fix to filter down.
> >
> > In the mean time, I guess we should discuss whether syzbot should
> > really be posting scans of downstream trees to upstream lists.
> 
> In this particular case, syzbot has captured all the recipients from
> the patch email [1], because that email Cc'd
> syzbot+15cd994e273307bf5cfa@...kaller.appspotmail.com. To syzbot, all
> these people were involved in the original bug discussion, and so it
> notified them about the problem.
> 
> FWIW I've sent a PR[2] to make the "I can't find it in any tested
> tree" message include the link to the syzkaller dashboard. Hopefully
> it will help resolve such confusions faster.

That's helpful, thank you.

-- 
Lee Jones [李琼斯]