linux-kernel - Re: fanotify use after free.

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Message-ID: <20140123150501.GC28796@quack.suse.cz>
Date:	Thu, 23 Jan 2014 16:05:01 +0100
From:	Jan Kara <jack@...e.cz>
To:	Dave Jones <davej@...hat.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jan Kara <jack@...e.cz>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Jiri Kosina <jkosina@...e.cz>
Subject: Re: fanotify use after free.

On Wed 22-01-14 19:32:40, Dave Jones wrote:
> On Wed, Jan 22, 2014 at 04:08:52PM -0800, Linus Torvalds wrote:
>  > On Wed, Jan 22, 2014 at 3:36 PM, Jan Kara <jack@...e.cz> wrote:
>  > >
>  > > But refcounting seems like an overkill for this - there is exactly one
>  > > fanotify_response_event structure iff it is a permission event. So
>  > > something like the (completely untested) attached patch should fix the
>  > > problem. But I agree it's a bit ugly so we might want something different.
>  > > I'll try to think about something better tomorrow.
>  > 
>  > Ok, In the meantime, Dave, can you verify whether this hacky patch
>  > fixes your problem?
> 
> It actually seems worse. I see the tail end of what looks like a slab corruption
> trace, and then a total lockup.  And of course none of this makes it over ttyUSB0
> because it happens so early. Grr.
  Drat. Since this seems reasonably reproducible, I'll try to reproduce
and debug this (it seems systemd is using fanotify in a way that triggers
this). Thanks for testing.

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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