From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757287Ab0CPFrf (ORCPT ); Tue, 16 Mar 2010 01:47:35 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:58340 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753218Ab0CPFrd (ORCPT ); Tue, 16 Mar 2010 01:47:33 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 From: KOSAKI Motohiro To: kiran@scalex86.org Subject: Re: + tmpfs-fix-oops-on-remounts-with-mpol=default.patch added to -mm tree Cc: kosaki.motohiro@jp.fujitsu.com, cl@linux-foundation.org, hugh.dickins@tiscali.co.uk, lee.schermerhorn@hp.com, mel@csn.ul.ie, stable@kernel.org, LKML , linux-mm , akpm@linux-foundation.org In-Reply-To: <201003122353.o2CNrC56015250@imap1.linux-foundation.org> References: <201003122353.o2CNrC56015250@imap1.linux-foundation.org> Message-Id: <20100316143406.4C45.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.50.07 [ja] Date: Tue, 16 Mar 2010 14:47:30 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > ------------------------------------------------------ > Subject: tmpfs: fix oops on remounts with mpol=default > From: Ravikiran G Thirumalai > > Fix an 'oops' when a tmpfs mount point is remounted with the 'default' > mempolicy. > > Upon remounting a tmpfs mount point with 'mpol=default' option, the > remount code crashed with a null pointer dereference. The initial problem > report was on 2.6.27, but the problem exists in mainline 2.6.34-rc as > well. On examining the code, we see that mpol_new returns NULL if default > mempolicy was requested. This 'NULL' mempolicy is accessed to store the > node mask resulting in oops. > > The following patch fixes the oops by avoiding dereferencing NULL if the > new mempolicy is NULL. The patch also sets 'err' to 0 if MPOL_DEFAULT is > passed (err is initialized to 1 initially at mpol_parse_str()) Hi Ravikiran, I'm glad to your contribution. Unfortunately I've found various related issue in mpol_parse_str() while reviewing your patch. So, I'll post updated patches. - kosaki > > Signed-off-by: Ravikiran Thirumalai > Cc: KOSAKI Motohiro > Cc: Christoph Lameter > Cc: Mel Gorman > Cc: Lee Schermerhorn > Cc: Hugh Dickins > Cc: > Signed-off-by: Andrew Morton > --- > > mm/mempolicy.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff -puN mm/mempolicy.c~tmpfs-fix-oops-on-remounts-with-mpol=default mm/mempolicy.c > --- a/mm/mempolicy.c~tmpfs-fix-oops-on-remounts-with-mpol=default > +++ a/mm/mempolicy.c > @@ -2213,10 +2213,14 @@ int mpol_parse_str(char *str, struct mem > goto out; > mode = MPOL_PREFERRED; > break; > - > + case MPOL_DEFAULT: > + /* > + * mpol_new() enforces empty nodemask, ignores flags. > + */ > + err = 0; > + break; > /* > * case MPOL_BIND: mpol_new() enforces non-empty nodemask. > - * case MPOL_DEFAULT: mpol_new() enforces empty nodemask, ignores flags. > */ > } > > @@ -2250,7 +2254,7 @@ int mpol_parse_str(char *str, struct mem > if (ret) { > err = 1; > mpol_put(new); > - } else if (no_context) { > + } else if (no_context && new) { > /* save for contextualization */ > new->w.user_nodemask = nodes; > } > _ > > Patches currently in -mm which might be from kiran@scalex86.org are > > tmpfs-fix-oops-on-remounts-with-mpol=default.patch > slab-leaks3-default-y.patch >