config: Fix parsing of mount options

When parsing mount options e.g. from lxc.mount.entry the specified
options are mapped to the flags constants. To do so, the strings
are compared to the options contained in mount_opt. However,
when comparing the strings, the length of the string is not
checked. That entails that the option "rootcontext=selinux-context"
is mapped to the mount option read-only (ro). This commit fixes
this issue by checking if a '=' is contained in the specified option
and additionally comparing the length of the strings.

Signed-off-by: Maximilian Blenk <Maximilian.Blenk@bmw.de>

src/lxc/conf.c

@@ -1825,16 +1825,21 @@ static void parse_mntopt(char *opt, unsigned long *flags, char **data, size_t si
 {
 	struct mount_opt *mo;
 
-	/* If opt is found in mount_opt, set or clear flags.
-	 * Otherwise append it to data. */
-
-	for (mo = &mount_opt[0]; mo->name != NULL; mo++) {
-		if (strncmp(opt, mo->name, strlen(mo->name)) == 0) {
-			if (mo->clear)
-				*flags &= ~mo->flag;
-			else
-				*flags |= mo->flag;
-			return;
+	/* If '=' is contained in opt, the option must go into data. */
+	if (!strchr(opt, '=')) {
+
+		/* If opt is found in mount_opt, set or clear flags.
+		 * Otherwise append it to data. */
+		size_t opt_len = strlen(opt);
+		for (mo = &mount_opt[0]; mo->name != NULL; mo++) {
+			size_t mo_name_len = strlen(mo->name);
+			if (opt_len == mo_name_len && strncmp(opt, mo->name, mo_name_len) == 0) {
+				if (mo->clear)
+					*flags &= ~mo->flag;
+				else
+					*flags |= mo->flag;
+				return;
+			}
 		}
 	}