From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751525AbcFXUTr (ORCPT ); Fri, 24 Jun 2016 16:19:47 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:39497 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751121AbcFXUTp (ORCPT ); Fri, 24 Jun 2016 16:19:45 -0400 Date: Fri, 24 Jun 2016 13:19:44 -0700 From: Andrew Morton To: Vlastimil Babka Cc: js1304@gmail.com, mgorman@techsingularity.net, Minchan Kim , Alexander Potapenko , Hugh Dickins , Michal Hocko , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Sasha Levin , Sudip Mukherjee , Sudip Mukherjee , Joonsoo Kim Subject: Re: [PATCH v3 7/9] mm/page_owner: avoid null pointer dereference Message-Id: <20160624131944.cf98a963de76938246a27e13@linux-foundation.org> In-Reply-To: <09cfe295-87d0-16d9-36ed-458378b3bd05@suse.cz> References: <1466150259-27727-1-git-send-email-iamjoonsoo.kim@lge.com> <1466150259-27727-8-git-send-email-iamjoonsoo.kim@lge.com> <09cfe295-87d0-16d9-36ed-458378b3bd05@suse.cz> X-Mailer: Sylpheed 3.4.1 (GTK+ 2.24.23; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 17 Jun 2016 15:32:20 +0200 Vlastimil Babka wrote: > On 06/17/2016 09:57 AM, js1304@gmail.com wrote: > > From: Sudip Mukherjee > > > > We have dereferenced page_ext before checking it. Lets check it first > > and then used it. > > > > Link: http://lkml.kernel.org/r/1465249059-7883-1-git-send-email-sudipm.mukherjee@gmail.com > > Signed-off-by: Sudip Mukherjee > > Signed-off-by: Joonsoo Kim > > Hmm, this is already in mmotm as > http://www.ozlabs.org/~akpm/mmotm/broken-out/mm-page_owner-use-stackdepot-to-store-stacktrace-fix.patch > > But imho it's fixing a problem not related to your patch, but something that the > commit f86e4271978b missed. So it should separately go to 4.7 ASAP. > > Acked-by: Vlastimil Babka > Fixes: f86e4271978b ("mm: check the return value of lookup_page_ext for all call > sites") Thanks, I reordered Sudip's patch. From: Sudip Mukherjee Subject: mm/page_owner: avoid null pointer dereference We have dereferenced page_ext before checking it. Lets check it first and then used it. Fixes: f86e4271978b ("mm: check the return value of lookup_page_ext for all call sites") Link: http://lkml.kernel.org/r/1465249059-7883-1-git-send-email-sudipm.mukherjee@gmail.com Signed-off-by: Sudip Mukherjee Acked-by: Vlastimil Babka Cc: Joonsoo Kim Signed-off-by: Andrew Morton --- mm/page_owner.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff -puN mm/page_owner.c~mm-page_owner-use-stackdepot-to-store-stacktrace-fix mm/page_owner.c --- a/mm/page_owner.c~mm-page_owner-use-stackdepot-to-store-stacktrace-fix +++ a/mm/page_owner.c @@ -207,13 +207,15 @@ void __dump_page_owner(struct page *page .nr_entries = page_ext->nr_entries, .entries = &page_ext->trace_entries[0], }; - gfp_t gfp_mask = page_ext->gfp_mask; - int mt = gfpflags_to_migratetype(gfp_mask); + gfp_t gfp_mask; + int mt; if (unlikely(!page_ext)) { pr_alert("There is not page extension available.\n"); return; } + gfp_mask = page_ext->gfp_mask; + mt = gfpflags_to_migratetype(gfp_mask); if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags)) { pr_alert("page_owner info is not active (free page?)\n"); _