cifscreds: check optind before accessing argv[optind]

Redhat bugzilla: 1278543

This fixes a segfault for some incorrect usage, for example
   cifscreds -u test

Reviewed-by: Steve French <smfrench@gmail.com>
Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/cifscreds.c b/cifscreds.c
index 5d84c3c..32f2ee4 100644
--- a/cifscreds.c
+++ b/cifscreds.c
@@ -487,6 +487,9 @@ int main(int argc, char **argv)
 		}
 	}
 
+	if (optind >= argc)
+		return usage();
+
 	/* find the best fit command */
 	best = NULL;
 	n = strnlen(argv[optind], MAX_COMMAND_SIZE);