linux-ext4 - Re: [patch]check NULL pointer

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Date:	Mon, 13 Jun 2011 15:30:58 +0800
From:	Shaohua Li <shaohua.li@...el.com>
To:	Lukas Czerner <lczerner@...hat.com>
Cc:	Eric Sandeen <sandeen@...hat.com>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
	Ted Ts'o <tytso@....edu>
Subject: Re: [patch]check NULL pointer

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 <shaohua.li@...el.com>

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 ? : ";");
 
 	if (es->s_error_count)
 		mod_timer(&sbi->s_err_report, jiffies + 300*HZ); /* 5 minutes */
@@ -4443,7 +4443,7 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
 	if (enable_quota)
 		dquot_resume(sb, -1);
 
-	ext4_msg(sb, KERN_INFO, "re-mounted. Opts: %s", orig_data);
+	ext4_msg(sb, KERN_INFO, "re-mounted. Opts: %s", orig_data ? : ";");
 	kfree(orig_data);
 	return 0;
 


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