linux-kernel - Re: WARNING: syz-executor still has locks held!

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Message-ID: <20190320131655.GA8696@dhcp22.suse.cz>
Date:   Wed, 20 Mar 2019 14:16:55 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     syzbot <syzbot+b70f2aabc707c69c9239@...kaller.appspotmail.com>
Cc:     chanho.min@....com, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, oleg@...hat.com, pavel@....cz,
        rafael.j.wysocki@...el.com, syzkaller-bugs@...glegroups.com,
        viro@...iv.linux.org.uk
Subject: Re: WARNING: syz-executor still has locks held!

On Wed 20-03-19 05:24:00, syzbot wrote:
> syzbot has bisected this bug to:
> 
> commit c22397888f1eed98cd59f0a88f2a5f6925f80e15
> Author: Chanho Min <chanho.min@....com>
> Date:   Mon Nov 12 03:54:45 2018 +0000
> 
>     exec: make de_thread() freezable
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=14ee6217200000
> start commit:   c2239788 exec: make de_thread() freezable
> git tree:       upstream
> final crash:    https://syzkaller.appspot.com/x/report.txt?x=16ee6217200000
> console output: https://syzkaller.appspot.com/x/log.txt?x=12ee6217200000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=73e2bc0cb6463446
> dashboard link: https://syzkaller.appspot.com/bug?extid=b70f2aabc707c69c9239
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16c9e26d400000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14e1234d400000
> 
> Reported-by: syzbot+b70f2aabc707c69c9239@...kaller.appspotmail.com
> Fixes: c2239788 ("exec: make de_thread() freezable")

Yes we do hold the cgred mutex while calling freezable_schedule but why
are we getting a warning is not really clear to me. The task should be
hidden from the freezer so why do we warn at all?
-- 
Michal Hocko
SUSE Labs