[PATCH 4.9 118/125] ovl: fix random return value on mount

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Amir Goldstein <amir73il@xxxxxxxxx>

commit 8fc646b44385ff0a9853f6590497e43049eeb311 upstream.

On failure to prepare_creds(), mount fails with a random
return value, as err was last set to an integer cast of
a valid lower mnt pointer or set to 0 if inodes index feature
is enabled.

Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Fixes: 3fe6e52f0626 ("ovl: override creds with the ones from ...")
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/overlayfs/super.c |    1 +
 1 file changed, 1 insertion(+)

--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1310,6 +1310,7 @@ static int ovl_fill_super(struct super_b
 	else
 		sb->s_d_op = &ovl_dentry_operations;
 
+	err = -ENOMEM;
 	ufs->creator_cred = cred = prepare_creds();
 	if (!cred)
 		goto out_put_lower_mnt;