From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753043AbdJ3WNU (ORCPT ); Mon, 30 Oct 2017 18:13:20 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:51283 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752949AbdJ3WNT (ORCPT ); Mon, 30 Oct 2017 18:13:19 -0400 Subject: Re: [Jfs-discussion] [PATCH] jfs: Add missing NULL pointer check in __get_metapage To: Juerg Haefliger , jfs-discussion@lists.sourceforge.net, linux-kernel@vger.kernel.org References: <20171004082441.2405-1-juerg.haefliger@canonical.com> <1dbf4a54-968f-0ca7-da96-e262c653fecb@canonical.com> From: Dave Kleikamp Message-ID: Date: Mon, 30 Oct 2017 17:13:07 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <1dbf4a54-968f-0ca7-da96-e262c653fecb@canonical.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Source-IP: userv0021.oracle.com [156.151.31.71] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/25/2017 02:50 AM, Juerg Haefliger wrote: > Is this a patch you might consider? Sorry it's taken me so long to respond. I don't think this is the right fix. A failed allocation will still result in a null pointer dereference by the caller, __get_metapage(). I think the check needs to be put there. Like this: --- a/fs/jfs/jfs_metapage.c +++ b/fs/jfs/jfs_metapage.c @@ -663,6 +663,8 @@ struct metapage *__get_metapage(struct inode *inode, unsigned long lblock, } else { INCREMENT(mpStat.pagealloc); mp = alloc_metapage(GFP_NOFS); + if (!mp) + goto unlock; mp->page = page; mp->sb = inode->i_sb; mp->flag = 0; Furthermore, it looks like all the callers of __get_metapage() check for a null return, so I'm not sure we need to handle the error at this point. I might have to look a bit harder at that, since there are many callers. Thanks, Shaggy > > Thanks > ...Juerg > > > On 10/04/2017 10:24 AM, Juerg Haefliger wrote: >> alloc_metapage can return a NULL pointer so check for that. And also emit >> an error message if that happens. >> >> Signed-off-by: Juerg Haefliger >> --- >> fs/jfs/jfs_metapage.c | 20 +++++++++++++------- >> 1 file changed, 13 insertions(+), 7 deletions(-) >> >> diff --git a/fs/jfs/jfs_metapage.c b/fs/jfs/jfs_metapage.c >> index 1c4b9ad4d7ab..00f21af66872 100644 >> --- a/fs/jfs/jfs_metapage.c >> +++ b/fs/jfs/jfs_metapage.c >> @@ -187,14 +187,18 @@ static inline struct metapage *alloc_metapage(gfp_t gfp_mask) >> { >> struct metapage *mp = mempool_alloc(metapage_mempool, gfp_mask); >> >> - if (mp) { >> - mp->lid = 0; >> - mp->lsn = 0; >> - mp->data = NULL; >> - mp->clsn = 0; >> - mp->log = NULL; >> - init_waitqueue_head(&mp->wait); >> + if (!mp) { >> + jfs_err("mempool_alloc failed!\n"); >> + return NULL; >> } >> + >> + mp->lid = 0; >> + mp->lsn = 0; >> + mp->data = NULL; >> + mp->clsn = 0; >> + mp->log = NULL; >> + init_waitqueue_head(&mp->wait); >> + >> return mp; >> } >> >> @@ -663,6 +667,8 @@ struct metapage *__get_metapage(struct inode *inode, unsigned long lblock, >> } else { >> INCREMENT(mpStat.pagealloc); >> mp = alloc_metapage(GFP_NOFS); >> + if (!mp) >> + goto unlock; >> mp->page = page; >> mp->sb = inode->i_sb; >> mp->flag = 0; >>