From patchwork Tue Jan 17 15:12:33 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Christoph Lameter (Ampere)" X-Patchwork-Id: 136486 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id D9A3BB6EFF for ; Wed, 18 Jan 2012 02:13:14 +1100 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754725Ab2AQPMw (ORCPT ); Tue, 17 Jan 2012 10:12:52 -0500 Received: from smtp110.prem.mail.ac4.yahoo.com ([76.13.13.93]:36016 "HELO smtp110.prem.mail.ac4.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1754401Ab2AQPMu (ORCPT ); Tue, 17 Jan 2012 10:12:50 -0500 Received: (qmail 53619 invoked from network); 17 Jan 2012 15:12:49 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.com; s=s1024; t=1326813169; bh=Z5eZEjOimJqU88YW6ntMJ6hhFmIyjko9+nTgTB7auQ0=; h=X-Yahoo-Newman-Property:X-YMail-OSG:X-Yahoo-SMTP:Received:Received:Date:From:X-X-Sender:To:cc:Subject:In-Reply-To:Message-ID:References:User-Agent:MIME-Version:Content-Type; b=KVIzBADlykMyZmAh8csVt7eVeOb6486fJPhqCd6LirOKA9NMhzbX4baX2zS5fFJaTyCv/g5ShcVeWUAB39E3tuCY6xdjTj0NSH4itT4PztmnKLcRWmiSGAb74xzqEECeURNsYkv3BAk015ZNzrHjJEq9XBhHeMYCL2Nqo5t+Ne4= X-Yahoo-Newman-Property: ymail-3 X-YMail-OSG: SjMgG00VM1kYslN0ftH1ESqhjsm3HRdcFDUFhUwUwx4E4iP ARMTLH08FxkvqgYC3sml3lQxTz1XAUi.gDl74KWWqTsDL4p.Xe0.avQvUWFF ybOyUpoSjjYUmnhfYrG_TLKXgtpW5t5ovUhK1scFMa5mg9K5jdqIe0akt0cn 0bMbwRKM9l.JdUNDBNFJWjJfBTLEUpDe1uxJexsf8Y5Lf1q.rJ855y.Upcse Mx0TGsTw8cEQX0ohAN50K9AhCmBY_NlaIeU559H4u8MYqo5CaaQiXhl_TEOF VDejzbORXYJNuNMgSMe8FTRiBhimIOCNkwJuH7SloGEAJVRUjqOMtLeNxMrI fweGigRoYKTfU1fuRkl.8yATZD6zJFymNJKpUPTjLl6tuTkfPc68sSBXN5Ci s3tsDcWOkIH95Bwyv39vy0z69yx9HiKu4NZHA X-Yahoo-SMTP: _Dag8S.swBC1p4FJKLCXbs8NQzyse1SYSgnAbY0- Received: from router.home (cl@99.30.10.212 with plain) by smtp110.prem.mail.ac4.yahoo.com with SMTP; 17 Jan 2012 07:12:48 -0800 PST Received: from cl (helo=localhost) by router.home with local-esmtp (Exim 4.71) (envelope-from ) id 1RnAiL-0001Jt-HF; Tue, 17 Jan 2012 09:12:45 -0600 Date: Tue, 17 Jan 2012 09:12:33 -0600 (CST) From: Christoph Lameter X-X-Sender: cl@router.home To: Eric Dumazet 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 Subject: Re: Hung task when calling clone() due to netfilter/slab In-Reply-To: <1326648305.5287.78.camel@edumazet-laptop> Message-ID: References: <1326558605.19951.7.camel@lappy> <1326561043.5287.24.camel@edumazet-laptop> <1326632384.11711.3.camel@lappy> <1326648305.5287.78.camel@edumazet-laptop> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 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 Reported-by: Sasha Levin --- mm/slub.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html 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);