From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mo-p00-ob.rzone.de ([81.169.146.162]:15981 "EHLO mo-p00-ob.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751962Ab2G0LJ4 (ORCPT ); Fri, 27 Jul 2012 07:09:56 -0400 Message-ID: <50127701.7040603@giantdisaster.de> Date: Fri, 27 Jul 2012 13:09:53 +0200 From: Stefan Behrens MIME-Version: 1.0 To: Nageswara R Sastry CC: linux-btrfs@vger.kernel.org, chandanrmail@gmail.com Subject: Re: [PATCH] btrfs-progs: btrfs-image.c: Added NULL pointer check. References: <1343385254-8299-1-git-send-email-nasastry@in.ibm.com> In-Reply-To: <1343385254-8299-1-git-send-email-nasastry@in.ibm.com> Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Fri, 27 Jul 2012 16:04:14 +0530, Nageswara R Sastry wrote: > Check for the return value of 'open_ctree()' before dereferencing it. > > Signed-off-by: Nageswara R Sastry > --- > btrfs-image.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/btrfs-image.c b/btrfs-image.c > index f2bbcc8..2a33a55 100644 > --- a/btrfs-image.c > +++ b/btrfs-image.c > @@ -491,6 +491,7 @@ static int create_metadump(const char *input, FILE *out, int num_threads, > int ret; > > root = open_ctree(input, 0, 0); > + BUG_ON(!root); > BUG_ON(root->nodesize != root->leafsize); > > ret = metadump_init(&metadump, root, out, num_threads, > In general, explicit BUG_ON() checks for a NULL pointer are not added to the Linux kernel if the pointer is dereferenced afterwards. When the NULL area is accessed, you get a general protection fault including the call trace and a dump of all registers. Adding explicit BUG_ON(ptr != NULL) adds overhead without bringing any additional information.