dns_resolver: avoid pointless cred reference count bump

The dns_resolver_cache creds hold a long-term reference that is stable
during the operation.

Link: https://lore.kernel.org/r/20241125-work-cred-v2-26-68b9d38bb5b2@kernel.org
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: brauner

net/dns_resolver/dns_query.c

@@ -124,9 +124,9 @@ int dns_query(struct net *net,
 	/* make the upcall, using special credentials to prevent the use of
 	 * add_key() to preinstall malicious redirections
 	 */
-	saved_cred = override_creds(get_new_cred(dns_resolver_cache));
+	saved_cred = override_creds(dns_resolver_cache);
 	rkey = request_key_net(&key_type_dns_resolver, desc, net, options);
-	put_cred(revert_creds(saved_cred));
+	revert_creds(saved_cred);
 	kfree(desc);
 	if (IS_ERR(rkey)) {
 		ret = PTR_ERR(rkey);