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From: Christoph Lameter <cl@linux.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Sasha Levin <levinsasha928@gmail.com>,
	Dave Jones <davej@redhat.com>, davem <davem@davemloft.net>,
	Pekka Enberg <penberg@kernel.org>, Matt Mackall <mpm@selenic.com>,
	kaber@trash.net, pablo@netfilter.org,
	linux-kernel <linux-kernel@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>,
	netfilter-devel@vger.kernel.org, netdev <netdev@vger.kernel.org>
Subject: Re: Hung task when calling clone() due to netfilter/slab
Date: Tue, 17 Jan 2012 09:27:31 -0600 (CST)	[thread overview]
Message-ID: <alpine.DEB.2.00.1201170927020.4800@router.home> (raw)
In-Reply-To: <1326813630.2259.19.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC>

On Tue, 17 Jan 2012, Eric Dumazet wrote:

> 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 <levinsasha928@gmail.com>


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.

Reported-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Christoph Lameter <cl@linux.com>

---
 mm/slub.c |    3 ++-
 1 file changed, 2 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 03:26:06.799986908 -0600
@@ -3929,13 +3929,14 @@ 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);
 				kfree(n);
 				kfree(s);
 				goto err;
 			}
-			up_write(&slub_lock);
 			return s;
 		}
 		kfree(n);

  reply	other threads:[~2012-01-17 15:27 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-01-14 16:30 Hung task when calling clone() due to netfilter/slab Sasha Levin
2012-01-14 17:10 ` Eric Dumazet
2012-01-14 17:18   ` Eric Dumazet
2012-01-15 12:59   ` Sasha Levin
2012-01-15 17:25     ` Eric Dumazet
2012-01-17 15:12       ` Christoph Lameter
2012-01-17 15:20         ` Eric Dumazet
2012-01-17 15:27           ` Christoph Lameter [this message]
2012-01-17 15:30             ` Eric Dumazet
2012-01-17 16:04               ` Christoph Lameter
2012-01-17 22:22                 ` Christoph Lameter
2012-01-19 21:43                   ` Eric W. Biederman
2012-01-19 22:15                     ` Eric W. Biederman
2012-01-20  2:03                       ` Christoph Lameter
2012-01-20  2:31                         ` Eric W. Biederman
2012-01-20 14:49                           ` Christoph Lameter
2012-01-20 20:40                             ` Eric W. Biederman
2012-02-01  8:05                             ` Pekka Enberg
2012-02-01 17:32                               ` Eric W. Biederman
2012-02-01  8:07               ` Pekka Enberg

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