net: vxlan: Free a leaked vetoed multicast rdst

When an rdst is rejected by a driver, the current code removes it from
the remote list, but neglects to free it. This is triggered by
tools/testing/selftests/drivers/net/mlxsw/vxlan_fdb_veto.sh and shows as
the following kmemleak trace:

unreferenced object 0xffff88817fa3d888 (size 96):
  comm "softirq", pid 0, jiffies 4372702718 (age 165.252s)
  hex dump (first 32 bytes):
    02 00 00 00 c6 33 64 03 80 f5 a2 61 81 88 ff ff  .....3d....a....
    06 df 71 ae ff ff ff ff 0c 00 00 00 04 d2 6a 6b  ..q...........jk
  backtrace:
    [<00000000296b27ac>] kmem_cache_alloc_trace+0x1ae/0x370
    [<0000000075c86dc6>] vxlan_fdb_append.part.12+0x62/0x3b0 [vxlan]
    [<00000000e0414b63>] vxlan_fdb_update+0xc61/0x1020 [vxlan]
    [<00000000f330c4bd>] vxlan_fdb_add+0x2e8/0x3d0 [vxlan]
    [<0000000008f81c2c>] rtnl_fdb_add+0x4c2/0xa10
    [<00000000bdc4b270>] rtnetlink_rcv_msg+0x6dd/0x970
    [<000000006701f2ce>] netlink_rcv_skb+0x290/0x410
    [<00000000c08a5487>] rtnetlink_rcv+0x15/0x20
    [<00000000d5f54b1e>] netlink_unicast+0x43f/0x5e0
    [<00000000db4336bb>] netlink_sendmsg+0x789/0xcd0
    [<00000000e1ee26b6>] sock_sendmsg+0xba/0x100
    [<00000000ba409802>] ___sys_sendmsg+0x631/0x960
    [<000000003c332113>] __sys_sendmsg+0xea/0x180
    [<00000000f4139144>] __x64_sys_sendmsg+0x78/0xb0
    [<000000006d1ddc59>] do_syscall_64+0x94/0x410
    [<00000000c8defa9a>] entry_SYSCALL_64_after_hwframe+0x49/0xbe

Move vxlan_dst_free() up and schedule a call thereof to plug this leak.

Fixes: 61f46fe8 ("vxlan: Allow vetoing of FDB notifications")
Signed-off-by: Petr Machata <petrm@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/vxlan.c

@@ -869,6 +869,14 @@ static void vxlan_fdb_destroy(struct vxlan_dev *vxlan, struct vxlan_fdb *f,
 	call_rcu(&f->rcu, vxlan_fdb_free);
 }
 
+static void vxlan_dst_free(struct rcu_head *head)
+{
+	struct vxlan_rdst *rd = container_of(head, struct vxlan_rdst, rcu);
+
+	dst_cache_destroy(&rd->dst_cache);
+	kfree(rd);
+}
+
 static int vxlan_fdb_update_existing(struct vxlan_dev *vxlan,
 				     union vxlan_addr *ip,
 				     __u16 state, __u16 flags,
@@ -941,8 +949,10 @@ static int vxlan_fdb_update_existing(struct vxlan_dev *vxlan,
 err_notify:
 	if ((flags & NLM_F_REPLACE) && rc)
 		*rd = oldrd;
-	else if ((flags & NLM_F_APPEND) && rc)
+	else if ((flags & NLM_F_APPEND) && rc) {
 		list_del_rcu(&rd->list);
+		call_rcu(&rd->rcu, vxlan_dst_free);
+	}
 	return err;
 }
 
@@ -1013,14 +1023,6 @@ static int vxlan_fdb_update(struct vxlan_dev *vxlan,
 	}
 }
 
-static void vxlan_dst_free(struct rcu_head *head)
-{
-	struct vxlan_rdst *rd = container_of(head, struct vxlan_rdst, rcu);
-
-	dst_cache_destroy(&rd->dst_cache);
-	kfree(rd);
-}
-
 static void vxlan_fdb_dst_destroy(struct vxlan_dev *vxlan, struct vxlan_fdb *f,
 				  struct vxlan_rdst *rd, bool swdev_notify)
 {