KEYS: prevent NULL pointer dereference in find_asymmetric_key()

In find_asymmetric_key(), if all NULLs are passed in the id_{0,1,2}
arguments, the kernel will first emit WARN but then have an oops
because id_2 gets dereferenced anyway.

Add the missing id_2 check and move WARN_ON() to the final else branch
to avoid duplicate NULL checks.

Found by Linux Verification Center (linuxtesting.org) with Svace static
analysis tool.

Cc: [email protected] # v5.17+
Fixes: 7d30198 ("keys: X.509 public key issuer lookup without AKID")
Suggested-by: Sergey Shtylyov <[email protected]>
Signed-off-by: Roman Smirnov <[email protected]>
Reviewed-by: Sergey Shtylyov <[email protected]>
Reviewed-by: Jarkko Sakkinen <[email protected]>
Signed-off-by: Jarkko Sakkinen <[email protected]>

crypto/asymmetric_keys/asymmetric_type.c

@@ -60,17 +60,18 @@ struct key *find_asymmetric_key(struct key *keyring,
 	char *req, *p;
 	int len;
 
-	WARN_ON(!id_0 && !id_1 && !id_2);
-
 	if (id_0) {
 		lookup = id_0->data;
 		len = id_0->len;
 	} else if (id_1) {
 		lookup = id_1->data;
 		len = id_1->len;
-	} else {
+	} else if (id_2) {
 		lookup = id_2->data;
 		len = id_2->len;
+	} else {
+		WARN_ON(1);
+		return ERR_PTR(-EINVAL);
 	}
 
 	/* Construct an identifier "id:<keyid>". */