linux-kernel - Re: [PATCH] loop: prevent bdev freeing while device in use

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Message-ID: <20130402060804.GI21522@ZenIV.linux.org.uk>
Date:	Tue, 2 Apr 2013 07:08:04 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Anatol Pomozov <anatol.pomozov@...il.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ayan George <ayan@...n.net>, stable <stable@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Theodore Ts'o <tytso@....edu>, Salman Qazi <sqazi@...gle.com>,
	Guo Chao <yan@...ux.vnet.ibm.com>
Subject: Re: [PATCH] loop: prevent bdev freeing while device in use

On Mon, Apr 01, 2013 at 10:58:55PM -0700, Anatol Pomozov wrote:
> >>
> >> loop_set_fd/loop_clr_fd (and any other loop ioctl) is called under
> >> loop_device->lo_ctl_mutex.
> >
> > Ok, good enough for me, I applied it, and it's commit
> > c1681bf8a7b1b98edee8b862a42c19c4e53205fd in my tree.
> >
> > I assume it should go to stable too, because none of this is new, is
> > it? Did you check how far back this applies? I assume this goes back
> > pretty much forever, no?
> 
> I bisected kernel using test from my commit and it points to
> 4c823cc3d568277aa6340d8df6981e34f4c4dee5 (appeared in kernel 3.2).
> 
> But even despite i cannot repro the crash on 3.0-stable, the
> underlying issue (block_device is not locked) still exists there. So I
> think patch should go to stable as well.

... except that you are doing invalidate *after* having done bdput.  Which
is probably valid (we have the same bdev pinned down by opened file used
to issue the ioclt), but it's a really bad style; this should be in opposite
order.
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