From: Shaohua Li Subject: Re: [patch]check NULL pointer Date: Tue, 14 Jun 2011 08:31:13 +0800 Message-ID: <1308011473.15392.114.camel@sli10-conroe> References: <1307590292.15392.71.camel@sli10-conroe> <4DF0DE02.1090008@redhat.com> <1307687692.15392.79.camel@sli10-conroe> <1307950258.15392.113.camel@sli10-conroe> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Eric Sandeen , "linux-ext4@vger.kernel.org" , Ted Ts'o To: Lukas Czerner Return-path: Received: from mga03.intel.com ([143.182.124.21]:35588 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755437Ab1FNAbS (ORCPT ); Mon, 13 Jun 2011 20:31:18 -0400 In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: On Mon, 2011-06-13 at 17:20 +0800, Lukas Czerner wrote: > On Mon, 13 Jun 2011, Shaohua Li wrote: > > > On Fri, 2011-06-10 at 16:32 +0800, Lukas Czerner wrote: > > > On Fri, 10 Jun 2011, Shaohua Li wrote: > > > > > > > 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. > > > > > > I am sorry, but as I pointed out in previous mail this is not true. > > > *orig_data can be also NULL in the case that *data is NULL and hence > > > there is no reason for exiting with error. Also please use the subject > > > Eric suggested. > > Hmm, maybe we just don't use the pointer if it's NULl. it's just print > > info anyway. > > > > Subject: [patch]ext4: check NULL orig_data pointer for mount and remount > > > > orig_data could be NULL, because the memory allocation of kstrdup() > > could fail or data is NULL. Add the NULL check. > > > > Signed-off-by: Shaohua Li > > > > diff --git a/fs/ext4/super.c b/fs/ext4/super.c > > index cc5c157..68eba3b 100644 > > --- a/fs/ext4/super.c > > +++ b/fs/ext4/super.c > > @@ -3706,7 +3706,7 @@ no_journal: > > > > ext4_msg(sb, KERN_INFO, "mounted filesystem with%s. " > > "Opts: %s%s%s", descr, sbi->s_es->s_mount_opts, > > - *sbi->s_es->s_mount_opts ? "; " : "", orig_data); > > + *sbi->s_es->s_mount_opts ? "; " : "", orig_data ? : ";"); > > Hi, > > so you are trying resolve the problem when the allocation fails right ? > But what you do is not solving anything, but rather hiding it and it is > not different than we had before. > > So what about this: > > if (data && !orig_data) > return ret; how could this work? if data is NULL, orig_data will be NULL, the ext4_msg will still use a NULL pointer.