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From: David Chen <david.chen@osnexus.com>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: lkml <linux-kernel@vger.kernel.org>,
	linux-fsdevel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH] vfs: check i_count under lock in evict_inodes
Date: Mon, 11 Jul 2016 18:31:57 -0700	[thread overview]
Message-ID: <CAK1sfubpLBv3P5ttpuq1z+EyNGHFiiMEVLSCv5HoQ51f_pFHig@mail.gmail.com> (raw)
In-Reply-To: <20160712004623.GA14480@ZenIV.linux.org.uk>

Hi Al,

I'm not sure about the in-tree fs, but in zfsonlinux, it would offload
iput to a thread, so this would happen there. And it would wait for
the thread in put_super(), so that part is not a problem...

Thanks

2016-07-11 17:46 GMT-07:00 Al Viro <viro@zeniv.linux.org.uk>:
> On Mon, Jul 11, 2016 at 05:15:04PM -0700, Chunwei Chen wrote:
>> We need to check i_count again with i_lock held, because iput might re-add
>> i_count when lazytime is on. Without this check, we could end up with
>> double-free or use-after-free.
>
> Details, please.  Ideally - with a reproducer.  Who is calling that iput()
> at that point of generic_shutdown_super() (has to be another thread) and
> just what will happen if the same iput() is delayed until *after*
> evict_inodes(), all the way into ->put_super().  At which point there's
> no promise whatsoever that the data structures used by ->evict_inode()
> hadn't been already freed...
>

  reply	other threads:[~2016-07-12  1:31 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-07-12  0:15 [PATCH] vfs: check i_count under lock in evict_inodes Chunwei Chen
2016-07-12  0:46 ` Al Viro
2016-07-12  1:31   ` David Chen [this message]
2016-07-12  1:40     ` Christoph Hellwig
2016-07-12  5:26     ` Al Viro

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