linux-kernel - Re: fanotify use after free.

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Message-ID: <20140123235549.GA7363@quack.suse.cz>
Date:	Fri, 24 Jan 2014 00:55:49 +0100
From:	Jan Kara <jack@...e.cz>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	Jan Kara <jack@...e.cz>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: fanotify use after free.

On Thu 23-01-14 16:07:45, Jiri Kosina wrote:
> On Thu, 23 Jan 2014, Jan Kara 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?
> > > 
> > > I reported the same slab corruption yesterday as well here:
> > > 
> > > 	https://lkml.org/lkml/2014/1/22/173
> > > 
> > > With the patch applied, I am still seeing the slab corruption, preceeded 
> > > by GPF (which is not there without the patch) in 
> > > lockref_put_or_lock(&dentry->d_lockref) in dput():
> >   Hmm, OK. Can you please send me your .config? I'll try to reproduce this
> > myself.
> 
> Attached.
> 
> The userspace is systemd-based.
  Strange. I've installed systemd system (openSUSE 13.1) and it boots with
the latest Linus' kernel just fine (and I have at least FANOTIFY and
SLAB debugging set the same way as you). But it was only a KVM guest. I'll
try tomorrow with a physical machine I guess.

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