svcrpc: fix rare race on unix_domain creation

Note that "new" here is not yet fully initialized; auth_domain_put
should be called only on auth_domains that have actually been added to
the hash.

Before this fix, two attempts to add the same domain at once could
cause the hlist_del in auth_domain_put to fail.
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

net/sunrpc/svcauth_unix.c

@@ -38,6 +38,14 @@ struct unix_domain {
 
 extern struct auth_ops svcauth_unix;
 
+static void svcauth_unix_domain_release(struct auth_domain *dom)
+{
+	struct unix_domain *ud = container_of(dom, struct unix_domain, h);
+
+	kfree(dom->name);
+	kfree(ud);
+}
+
 struct auth_domain *unix_domain_find(char *name)
 {
 	struct auth_domain *rv;
@@ -47,7 +55,7 @@ struct auth_domain *unix_domain_find(char *name)
 	while(1) {
 		if (rv) {
 			if (new && rv != &new->h)
-				auth_domain_put(&new->h);
+				svcauth_unix_domain_release(new);
 
 			if (rv->flavour != &svcauth_unix) {
 				auth_domain_put(rv);
@@ -74,14 +82,6 @@ struct auth_domain *unix_domain_find(char *name)
 }
 EXPORT_SYMBOL_GPL(unix_domain_find);
 
-static void svcauth_unix_domain_release(struct auth_domain *dom)
-{
-	struct unix_domain *ud = container_of(dom, struct unix_domain, h);
-
-	kfree(dom->name);
-	kfree(ud);
-}
-
 
 /**************************************************
  * cache for IP address to unix_domain