tipc: bail out if key is abnormally long

tipc segfaults when called with an abnormally long key:

$ tipc node set key 0123456789abcdef0123456789abcdef0123456789abcdef
*** buffer overflow detected ***: terminated

Fix this returning an error if key length is longer than
TIPC_AEAD_KEYLEN_MAX.

Fixes: 24bee3bf97 ("tipc: add new commands to set TIPC AEAD key")
Signed-off-by: Andrea Claudi <aclaudi@redhat.com>
Signed-off-by: David Ahern <dsahern@kernel.org>

tipc/misc.c

@@ -113,6 +113,9 @@ int str2key(char *str, struct tipc_aead_key *key)
 	    }
 	}
 
+	if (len > TIPC_AEAD_KEYLEN_MAX)
+		return -1;
+
 	/* Obtain key: */
 	if (!ishex) {
 		key->keylen = len;