linux-kernel - Re: [PATCH V2] kthread: zero the kthread data structure

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Message-ID: <20171107193257.GB4164960@devbig577.frc2.facebook.com>
Date:   Tue, 7 Nov 2017 11:32:57 -0800
From:   Tejun Heo <tj@...nel.org>
To:     Shaohua Li <shli@...com>
Cc:     LKML <linux-kernel@...r.kernel.org>, Jens Axboe <axboe@...nel.dk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH V2] kthread: zero the kthread data structure

On Tue, Nov 07, 2017 at 11:09:50AM -0800, Shaohua Li wrote:
> kthread() could bail out early before we initialize blkcg_css (if the
> kthread is killed very early. Please see xchg() statement in kthread()),
> which confuses free_kthread_struct. Instead of moving the blkcg_css
> initialization early, we simply zero the whole 'self' data structure,
> which doesn't sound much overhead.
> 
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Fixes: 05e3db95ebfc ("kthread: add a mechanism to store cgroup info")
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Tejun Heo <tj@...nel.org>
> Cc: Dmitry Vyukov <dvyukov@...gle.com>
> Signed-off-by: Shaohua Li <shli@...com>

Acked-by: Tejun Heo <tj@...nel.org>

Thanks.

-- 
tejun