linux-kernel - Re: kmemcheck caught read from freed memory (cfq_free_io

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1207133961.8514.768.camel@twins>
Date:	Wed, 02 Apr 2008 12:59:21 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	paulmck@...ux.vnet.ibm.com
Cc:	Ingo Molnar <mingo@...e.hu>, Jens Axboe <jens.axboe@...cle.com>,
	Pekka J Enberg <penberg@...helsinki.fi>,
	Vegard Nossum <vegard.nossum@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: kmemcheck caught read from freed memory (cfq_free_io_context)

On Wed, 2008-04-02 at 03:55 -0700, Paul E. McKenney wrote:
> On Wed, Apr 02, 2008 at 09:28:46AM +0200, Ingo Molnar wrote:
> > 
> > * Jens Axboe <jens.axboe@...cle.com> wrote:
> > 
> > > On Wed, Apr 02 2008, Pekka J Enberg wrote:
> > > > On Wed, 2 Apr 2008, Jens Axboe wrote:
> > > > > Good catch, I wonder why it didn't complain in my testing. I've added a
> > > > > patch to fix that, please see it here:
> > > > 
> > > > You probably don't have kmemcheck in your kernel ;-)
> > > 
> > > Ehm no, you are right :)
> > 
> > ... and you can get kmemcheck by testing on x86.git/latest:
> > 
> >   http://people.redhat.com/mingo/x86.git/README
> > 
> > ;-)
> 
> I will check this when I get back to some bandwidth -- but in the meantime,
> does kmemcheck special-case SLAB_DESTROY_BY_RCU?  It is legal to access
> newly-freed items in that case, as long as you did rcu_read_lock()
> before gaining a reference to them and don't hold the reference past
> the matching rcu_read_unlock().

I don't think it does.

It would have to register an call_rcu callback itself in order to mark
it freed - and handle the race with the object being handed out again.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/