block: validate amount of arguments for the "autofs" command

Using argv[3] without checking argc value could result in undefined
behavior. It could result in a crash or accessing a NULL that separates
argv from envp on UNIX.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Acked-by: John Crispin <john@phrozen.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/block.c b/block.c
index 46050b4..a0bbf47 100644
--- a/block.c
+++ b/block.c
@@ -1157,6 +1157,10 @@ static int main_autofs(int argc, char **argv)
 		}
 		return 0;
 	}
+
+	if (argc < 4)
+		return -EINVAL;
+
 	return mount_action(argv[2], argv[3], TYPE_AUTOFS);
 }