cifs: fix handling of escaped ',' in the password mount argument

Passwords can contain ',' which are also used as the separator between
mount options. Mount.cifs will escape all ',' characters as the string ",,".
Update parsing of the mount options to detect ",," and treat it as a single
'c' character.

Fixes: 24e0a1eff9e2 ("cifs: switch to new mount api")
Cc: stable@vger.kernel.org # 5.11
Reported-by: Simon Taylor <simon@simon-taylor.me.uk>
Tested-by: Simon Taylor <simon@simon-taylor.me.uk>
Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 30 insertions, 13 deletions

diff --git a/fs/cifs/fs_context.c b/fs/cifs/fs_context.c
index 14c955a3000646..892f51a21278be 100644
--- a/fs/cifs/fs_context.c
+++ b/fs/cifs/fs_context.c
@@ -544,20 +544,37 @@ static int smb3_fs_context_parse_monolithic(struct fs_context *fc,
 
 	/* BB Need to add support for sep= here TBD */
 	while ((key = strsep(&options, ",")) != NULL) {
-		if (*key) {
-			size_t v_len = 0;
-			char *value = strchr(key, '=');
-
-			if (value) {
-				if (value == key)
-					continue;
-				*value++ = 0;
-				v_len = strlen(value);
-			}
-			ret = vfs_parse_fs_string(fc, key, value, v_len);
-			if (ret < 0)
-				break;
+		size_t len;
+		char *value;
+
+		if (*key == 0)
+			break;
+
+		/* Check if following character is the deliminator If yes,
+		 * we have encountered a double deliminator reset the NULL
+		 * character to the deliminator
+		 */
+		while (options && options[0] == ',') {
+			len = strlen(key);
+			strcpy(key + len, options);
+			options = strchr(options, ',');
+			if (options)
+				*options++ = 0;
 		}
+
+
+		len = 0;
+		value = strchr(key, '=');
+		if (value) {
+			if (value == key)
+				continue;
+			*value++ = 0;
+			len = strlen(value);
+		}
+
+		ret = vfs_parse_fs_string(fc, key, value, len);
+		if (ret < 0)
+			break;
 	}
 
 	return ret;