Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753170AbZJUMmD (ORCPT ); Wed, 21 Oct 2009 08:42:03 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752694AbZJUMmC (ORCPT ); Wed, 21 Oct 2009 08:42:02 -0400 Received: from victor.provo.novell.com ([137.65.250.26]:44607 "EHLO victor.provo.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752597AbZJUMmA (ORCPT ); Wed, 21 Oct 2009 08:42:00 -0400 Message-ID: <4ADF01E9.4030404@suse.de> Date: Wed, 21 Oct 2009 18:13:21 +0530 From: Suresh Jayaraman User-Agent: Thunderbird 2.0.0.23 (X11/20090817) MIME-Version: 1.0 To: Hugh Dickins CC: Rafael Wysocki , Jens Axboe , LKML , Andrew Morton Subject: Re: [PATCH] swapfile: avoid NULL pointer dereference in swapon when s_bdev is NULL References: <4AC1FC41.2060807@suse.de> <4AC492E2.7060205@suse.de> <4AC49B95.2040504@suse.de> <4ACC111A.8020500@suse.de> In-Reply-To: <4ACC111A.8020500@suse.de> X-Enigmail-Version: 0.95.7 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2303 Lines: 55 Suresh Jayaraman wrote: > Hugh Dickins wrote: >> On Thu, 1 Oct 2009, Suresh Jayaraman wrote: >>> Hugh Dickins wrote: >>>> On Thu, 1 Oct 2009, Suresh Jayaraman wrote: >>>>> The call sequence is add_to_swap() -> get_swap_page() -> scan_swap_map() >>>>> -> discard_swap_cluster() -> blkdev_issue_discard(). >>>>> >>>>> Wrapping the code around a NULL check fixes the Oops for me. >>>> That's odd: scan_swap_map() should only discard_swap_cluster() if >>>> SWP_DISCARDABLE got set, and your first patch made sure that it wasn't. >>> I forgot to mention, this is not on loopback NFS mount but an remote NFS >>> mount (so possibly s_bdev is not NULL) when doing swapon. The oops was >>> triggered when memhog program tries to use the swap space on the newly >>> created swapfile on NFS. I have not completely investigated the issue, >>> perhaps s_bdev is not being set when it ought to be.. >> I'm happy to see your first patch already in 2.6.32-rc3, but still >> suspicious of this second patch you sent afterwards. A quick skim >> through your patchset suggests 23/31 is probably responsible: > > Thanks for skimming through those patches. I noticed this already during > my review and thought I had already fixed this, but apparently I missed > out. I'll test after fixing this and report. Sorry about the delay. I tested by fixing SWP_FILE macro only now after returning from vacation. I was not able to reproduce this. Please ignore the second patch and it's no longer necessary as noted by Hugh already. Thanks, >> --- mmotm.orig/include/linux/swap.h >> +++ mmotm/include/linux/swap.h >> @@ -120,6 +120,7 @@ struct swap_extent { >> enum { >> SWP_USED = (1 << 0), /* is slot in swap_info[] used? */ >> SWP_WRITEOK = (1 << 1), /* ok to write to this swap? */ >> + SWP_FILE = (1 << 2), /* file swap area */ >> SWP_DISCARDABLE = (1 << 2), /* blkdev supports discard */ >> SWP_DISCARDING = (1 << 3), /* now discarding a free cluster */ >> SWP_SOLIDSTATE = (1 << 4), /* blkdev seeks are cheap */ >> >> Hugh > > Thanks, > -- Suresh Jayaraman -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/