From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx129.postini.com [74.125.245.129]) by kanga.kvack.org (Postfix) with SMTP id 8F1F26B00CC for ; Tue, 17 Jan 2012 10:20:34 -0500 (EST) Received: by wicr5 with SMTP id r5so3910285wic.14 for ; Tue, 17 Jan 2012 07:20:32 -0800 (PST) Message-ID: <1326813630.2259.19.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC> Subject: Re: Hung task when calling clone() due to netfilter/slab From: Eric Dumazet Date: Tue, 17 Jan 2012 16:20:30 +0100 In-Reply-To: References: <1326558605.19951.7.camel@lappy> <1326561043.5287.24.camel@edumazet-laptop> <1326632384.11711.3.camel@lappy> <1326648305.5287.78.camel@edumazet-laptop> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Mime-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Lameter Cc: Sasha Levin , Dave Jones , davem , Pekka Enberg , Matt Mackall , kaber@trash.net, pablo@netfilter.org, linux-kernel , linux-mm , netfilter-devel@vger.kernel.org, netdev Le mardi 17 janvier 2012 A 09:12 -0600, Christoph Lameter a A(C)crit : > On Sun, 15 Jan 2012, Eric Dumazet wrote: > > > As soon as the slub_lock is released, another thread can come and find > > the new kmem_cache. > > Slabs are not looked up by name. A pointer to kmem_cache is passed to slab > functions and that pointer is returned from kmem_cache_create(). The risk > is someone traversing the kmem_cach list which is only done from within slub. > > > Subject: slub: Do not hold slub_lock when calling sysfs_slab_add() > > sysfs_slab_add() calls various sysfs functions that actually may > end up in userspace doing all sorts of things. > > Release the slub_lock after adding the kmem_cache structure to the list. > At that point the address of the kmem_cache is not known so we are > guaranteed exlusive access to the following modifications to the > kmem_cache structure. > > If the sysfs_slab_add fails then reacquire the slub_lock to > remove the kmem_cache structure from the list. > > Signed-off-by: Christoph Lameter > > --- > mm/slub.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > Index: linux-2.6/mm/slub.c > =================================================================== > --- linux-2.6.orig/mm/slub.c 2012-01-17 03:07:11.140010438 -0600 > +++ linux-2.6/mm/slub.c 2012-01-17 03:07:19.532010264 -0600 > @@ -3929,13 +3929,15 @@ struct kmem_cache *kmem_cache_create(con > if (kmem_cache_open(s, n, > size, align, flags, ctor)) { > list_add(&s->list, &slab_caches); > + up_write(&slub_lock); > if (sysfs_slab_add(s)) { > + down_write(&slub_lock); > list_del(&s->list); > + up_write(&slub_lock); > kfree(n); > kfree(s); > goto err; > } > - up_write(&slub_lock); > return s; > } > kfree(n); Buggy patch, since "goto err;" is going to up_write(&slub_lock) again. Also Christoph, you forgot to add the very much needed : Reported-by: Sasha Levin -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org