[REPOST PATCH v3 1/2] ext4: fix possible null pointer dereference

[Ian Kent]

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@xxxxxxxxx>
Signed-off-by: Ian Kent <raven@xxxxxxxxxx>
---
 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 9a66abcca1a8..9f0ecb25c9a6 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);