From: Tejun Heo <tj@kernel.org>
To: Jan Kara <jack@suse.cz>
Cc: Wei Fang <fangwei1@huawei.com>,
akpm@linux-foundation.org, hannes@cmpxchg.org, hch@infradead.org,
linux-mm@kvack.org, stable@vger.kernel.org,
Jens Axboe <axboe@kernel.dk>
Subject: Re: [PATCH] mm: Fix a NULL dereference crash while accessing bdev->bd_disk
Date: Tue, 29 Nov 2016 11:43:50 -0500 [thread overview]
Message-ID: <20161129164350.GC19454@htj.duckdns.org> (raw)
In-Reply-To: <20161129093035.GC7550@quack2.suse.cz>
Hello, Jan.
On Tue, Nov 29, 2016 at 10:30:35AM +0100, Jan Kara wrote:
> > It's kinda weird that sync() is ends up accessing bdev's without any
> > synchronization. Can't we just make iterate_bdevs() grab bd_mutex and
> > verify bd_disk isn't NULL before calling into the callback?
>
> This reminded me I've already seen something like this and indeed I've
> already had a very similar discussion in March -
> https://patchwork.kernel.org/patch/8556941/
lol
> Holding bd_mutex in iterate_devs() works but still nothing protects from
> flusher thread just walking across the block device inode and trying to
> write it which would result in the very same oops.
Ah, right. We aren't implementing either sever or refcnted draining
semantics properly. I wonder whether we'd be able to retire the inode
synchronously during blkdev_put.
Thanks.
--
tejun
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next prev parent reply other threads:[~2016-11-29 16:43 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-26 2:06 [PATCH] mm: Fix a NULL dereference crash while accessing bdev->bd_disk Wei Fang
2016-11-28 10:07 ` Jan Kara
2016-11-28 15:57 ` Tejun Heo
2016-11-29 9:30 ` Jan Kara
2016-11-29 16:43 ` Tejun Heo [this message]
2016-11-30 9:50 ` Jan Kara
2016-11-29 1:58 ` Wei Fang
2016-11-30 9:51 ` Jan Kara
2016-12-01 2:30 ` Wei Fang
2016-12-01 8:18 ` Jan Kara
2016-11-29 23:08 ` Andrew Morton
2016-11-30 7:30 ` Jan Kara
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