From: Shaohua Li Subject: Re: [patch]check NULL pointer Date: Fri, 10 Jun 2011 14:34:52 +0800 Message-ID: <1307687692.15392.79.camel@sli10-conroe> References: <1307590292.15392.71.camel@sli10-conroe> <4DF0DE02.1090008@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Lukas Czerner , "linux-ext4@vger.kernel.org" , Ted Ts'o To: Eric Sandeen Return-path: Received: from mga09.intel.com ([134.134.136.24]:11101 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751803Ab1FJGez (ORCPT ); Fri, 10 Jun 2011 02:34:55 -0400 In-Reply-To: <4DF0DE02.1090008@redhat.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Thu, 2011-06-09 at 22:51 +0800, Eric Sandeen wrote: > On 6/9/11 4:24 AM, Lukas Czerner wrote: > > On Thu, 9 Jun 2011, Shaohua Li wrote: > > > >> orig_data could be NULL. > > > > Now, that is the commit description :). Could you please be more > > descriptive in the "descritpion" ? Also the subject is not right either, > > please see Documentation/SubmittingPatches > > Yes; if possible please use the commit message to describe how/why orig_data > can be NULL; a testcase if one exists; the resulting flaw (null pointer deref?) > etc. > > something like: > > Subject: [PATCH] ext4: check for NULL orig_data pointer in mount paths > > The orig_data pointer in ext4_fill_super() and ext4_remount() > can be null if < ??? >, which can lead to < ??? > in the mount > and remount paths. This can be demonstrated by < ??? >. > To avoid this, we can simply test for the null pointer > and return an error in ext4_fill_super() and ext4_remount(). I thought the reason is pretty straightforward, anyway here is the updated patch. Subject: [patch]ext4: check NULL pointer for mount and remount orig_data could be NULL, because the memory allocation of kstrdup() could fail. Add the NULL check. Signed-off-by: Shaohua Li diff --git a/fs/ext4/super.c b/fs/ext4/super.c index cc5c157..45fc255 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -3057,6 +3057,8 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO; ext4_group_t first_not_zeroed; + if (!orig_data) + return ret; sbi = kzalloc(sizeof(*sbi), GFP_KERNEL); if (!sbi) goto out_free_orig; @@ -4285,6 +4287,8 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data) #endif char *orig_data = kstrdup(data, GFP_KERNEL); + if (!orig_data) + return -ENOMEM; /* Store the original options */ lock_super(sb); old_sb_flags = sb->s_flags;