netdev - Re: [Bugme-new] [Bug 33502] New: Caught 64-bit read from uninitialized memory in __alloc

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: <alpine.DEB.2.00.1104200942020.9266@router.home>
Date:	Wed, 20 Apr 2011 09:42:59 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
cc:	Pekka Enberg <penberg@...helsinki.fi>, casteyde.christian@...e.fr,
	Andrew Morton <akpm@...ux-foundation.org>,
	netdev@...r.kernel.org, bugzilla-daemon@...zilla.kernel.org,
	bugme-daemon@...zilla.kernel.org,
	Vegard Nossum <vegardno@....uio.no>
Subject: Re: [Bugme-new] [Bug 33502] New: Caught 64-bit read from uninitialized
 memory in __alloc_skb

On Wed, 20 Apr 2011, Eric Dumazet wrote:

> Le mercredi 20 avril 2011 à 09:05 -0500, Christoph Lameter a écrit :
> > On Wed, 20 Apr 2011, Eric Dumazet wrote:
> >
> > > > Then, just disable SLUB_CMPXCHG_DOUBLE if KMEMCHECK is defined, as I did in my first patch.
> >
> > Ok your first patch seems to be the sanest approach.
> >
> > >  {
> > > @@ -1889,16 +1895,18 @@ static __always_inline void *slab_alloc(struct kmem_cache *s,
> > >  	struct kmem_cache_cpu *c;
> > >  #ifdef CONFIG_CMPXCHG_LOCAL
> > >  	unsigned long tid;
> > > -#else
> > > +#endif
> > > +#ifdef MASK_IRQ_IN_SLAB_ALLOC
> > >  	unsigned long flags;
> > >  #endif
> > >
> >
> > Yea well that does not bring us much.
>
> Well, we keep the fast free path ?
>
> only slab_alloc() would have to disable irqs for ~20 instructions.

Avoiding the irq handling yields the savings that improve the fastpath. if
you do both then there is only a regression left. So lets go with
disabling the CMPXCHG_LOCAL.