From: Ming Lei <ming.lei@redhat.com>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Boqun Feng <boqun.feng@gmail.com>,
Hillf Danton <hdanton@sina.com>,
syzbot <syzbot+4f789823c1abc5accf13@syzkaller.appspotmail.com>,
Joel Fernandes <joel@joelfernandes.org>,
Lai Jiangshan <laijs@linux.alibaba.com>,
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com,
quic_neeraju@quicinc.com, frederic@kernel.org, urezki@gmail.com,
Jens Axboe <axboe@kernel.dk>
Subject: Re: [syzbot] KASAN: use-after-free Read in srcu_invoke_callbacks
Date: Fri, 14 Jan 2022 23:58:24 +0800 [thread overview]
Message-ID: <YeGdoAFYGhg3viPZ@T590> (raw)
In-Reply-To: <20220114152752.GU947480@paulmck-ThinkPad-P17-Gen-1>
On Fri, Jan 14, 2022 at 07:27:52AM -0800, Paul E. McKenney wrote:
> On Fri, Jan 14, 2022 at 10:38:42PM +0800, Boqun Feng wrote:
> > Hi,
> >
> > On Tue, Jan 11, 2022 at 11:05:00AM -0800, Paul E. McKenney wrote:
> > [...]
> > > > > The buggy address belongs to the object at ffff8880189b5c70
> > > > > which belongs to the cache request_queue_srcu of size 3816
> >
> > This cache name drew my attention when I was trying to look into this,
> > because I couldn't find it in v5.16, later on I realized the UAF was
> > found in linux-next and the commit introducing the cache was merged into
> > mainline if 5.17 merge window:
> >
> > 704b914f15fb blk-mq: move srcu from blk_mq_hw_ctx to request_queue
> >
> > I think the UAF is actually a bug introduced by the commit, because in
> > that commit srcu structure was moved from blk_mq_hw_ctx to
> > request_queue, and therefore the cleanup_srcu_struct() should be moved
> > from blk_mq_hw_sysfs_release() to blk_release_queue(), however the above
> > commit only deleted the one in blk_mq_hw_sysfs_release() but didn't add
> > a new one in blk_release_queue(). As a result when a request queue is
> > freed, the srcu structure is not fully clean up, therefore the UAF.
> >
> > IOW, something like below (untested) should fix this. Copy the auther
> > and block maintainers.
>
> One question for the author and block maintainers... Why not simply have
> a single srcu_struct for all of the queues? Or is there some situation
> where you need one queue's reader to avoid blocking other queues' SRCU
> grace periods?
Because srcu_struct is too fat, and only few drivers need it, and
most block drivers needn't it.
Thanks,
Ming
next prev parent reply other threads:[~2022-01-14 15:58 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-11 11:03 [syzbot] KASAN: use-after-free Read in srcu_invoke_callbacks syzbot
[not found] ` <20220111134324.1727-1-hdanton@sina.com>
2022-01-11 19:05 ` Paul E. McKenney
2022-01-14 14:38 ` Boqun Feng
2022-01-14 15:27 ` Paul E. McKenney
2022-01-14 15:58 ` Ming Lei [this message]
2022-01-14 16:11 ` Paul E. McKenney
2022-01-14 16:15 ` Ming Lei
2022-01-14 15:54 ` Ming Lei
[not found] ` <20220112094352.1785-1-hdanton@sina.com>
2022-01-12 17:12 ` Paul E. McKenney
2022-01-12 18:05 ` Paul E. McKenney
[not found] ` <20220113044938.1881-1-hdanton@sina.com>
2022-01-13 5:14 ` Paul E. McKenney
[not found] ` <20220113131256.1941-1-hdanton@sina.com>
2022-01-13 14:59 ` Paul E. McKenney
2022-01-13 3:19 ` Ming Lei
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