libsmack: fixed segfault in get_label() (regression in 66483b)

Commit 66483b introduced segfault in API functions smack_revoke_subject()
and smack_set_label_for_self().
Fix the accidental NULL pointer dereference.

diff --git a/libsmack/libsmack.c b/libsmack/libsmack.c
index 28c2715..32f1be3 100644 (file)
--- a/libsmack/libsmack.c
+++ b/libsmack/libsmack.c
@@ -740,7 +740,7 @@ static inline ssize_t get_label(char *dest, const char *src)
                        dest[i] = src[i];
        }
 
-       if (i < (SMACK_LABEL_LEN + 1))
+       if (dest && i < (SMACK_LABEL_LEN + 1))
                dest[i] = '\0';
 
        return i < (SMACK_LABEL_LEN + 1) ? i : -1;