[CIFS] Add destroy routine for dns_resolver

Otherwise, we're leaking the payload memory.

CC: Stable Kernel <stable@vger.kernel.org>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/CHANGES

@@ -8,7 +8,8 @@ architectures.  Fix problems with preserving timestamps on copying open
 files (e.g. "cp -a") to Windows servers.  For mkdir and create honor setgid bit
 on parent directory when server supports Unix Extensions but not POSIX
 create. Update cifs.upcall version to handle new Kerberos sec flags
-(this requires update of cifs.upcall program from Samba).
+(this requires update of cifs.upcall program from Samba).  Fix memory leak
+on dns_upcall (resolving DFS referralls).
 
 Version 1.53
 ------------

fs/cifs/dns_resolve.c

@@ -47,11 +47,18 @@ static int dns_resolver_instantiate(struct key *key, const void *data,
 	return rc;
 }
 
+static void
+dns_resolver_destroy(struct key *key)
+{
+	kfree(key->payload.data);
+}
+
 struct key_type key_type_dns_resolver = {
 	.name        = "dns_resolver",
 	.def_datalen = sizeof(struct in_addr),
 	.describe    = user_describe,
 	.instantiate = dns_resolver_instantiate,
+	.destroy     = dns_resolver_destroy,
 	.match       = user_match,
 };