media: firewire: Using uninitialized values in node_probe()

If fw_csr_string() returns -ENOENT, then "name" is uninitialized.  So
then the "strlen(model_names[i]) <= name_len" is true because strlen()
is unsigned and -ENOENT is type promoted to a very high positive value.
Then the "strncmp(name, model_names[i], name_len)" uses uninitialized
data because "name" is uninitialized.

Fixes: 92374e88 ("[media] firedtv: drop obsolete backend abstraction")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/firewire/firedtv-fw.c

@@ -272,6 +272,8 @@ static int node_probe(struct fw_unit *unit, const struct ieee1394_device_id *id)
 
 	name_len = fw_csr_string(unit->directory, CSR_MODEL,
 				 name, sizeof(name));
+	if (name_len < 0)
+		return name_len;
 	for (i = ARRAY_SIZE(model_names); --i; )
 		if (strlen(model_names[i]) <= name_len &&
 		    strncmp(name, model_names[i], name_len) == 0)