linux-kernel - [PATCH v3 1/2] ext4: fix possible null pointer dereference

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Date:   Mon, 25 Jul 2022 09:17:23 +0800
From:   Ian Kent <raven@...maw.net>
To:     Al Viro <viro@...IV.linux.org.uk>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Siddhesh Poyarekar <siddhesh@...plt.org>,
        David Howells <dhowells@...hat.com>,
        Miklos Szeredi <miklos@...redi.hu>,
        Carlos Maiolino <cmaiolino@...hat.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH v3 1/2] ext4: fix possible null pointer dereference

It could be the case that the file system parameter ->string value is
NULL rather than a zero length string.

Guard against this possibility in ext4_parse_param().

Reported-by: kernel test robot <oliver.sang@...el.com>
Signed-off-by: Ian Kent <raven@...maw.net>
---
 fs/ext4/super.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 845f2f8aee5f..97160e982ced 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2110,12 +2110,12 @@ static int ext4_parse_param(struct fs_context *fc, struct fs_parameter *param)
 	switch (token) {
 #ifdef CONFIG_QUOTA
 	case Opt_usrjquota:
-		if (!*param->string)
+		if (!param->string || !*param->string)
 			return unnote_qf_name(fc, USRQUOTA);
 		else
 			return note_qf_name(fc, USRQUOTA, param);
 	case Opt_grpjquota:
-		if (!*param->string)
+		if (!param->string || !*param->string)
 			return unnote_qf_name(fc, GRPQUOTA);
 		else
 			return note_qf_name(fc, GRPQUOTA, param);