tipc: fix a null pointer deref

In commit c55c8eda ("tipc: smooth change between replicast and
broadcast") we introduced new method to eliminate the risk of message
reordering that happen in between different nodes.
Unfortunately, we forgot checking at receiving side to ignore intra node.

We fix this by checking and returning if arrived message from intra node.

syzbot report:

==================================================================
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 7820 Comm: syz-executor418 Not tainted 5.0.0+ #61
Hardware name: Google Google Compute Engine/Google Compute Engine,
BIOS Google 01/01/2011
RIP: 0010:tipc_mcast_filter_msg+0x21b/0x13d0 net/tipc/bcast.c:782
Code: 45 c0 0f 84 39 06 00 00 48 89 5d 98 e8 ce ab a5 fa 49 8d bc
 24 c8 00 00 00 48 b9 00 00 00 00 00 fc ff df 48 89 f8 48 c1 e8 03
 <80> 3c 08 00 0f 85 9a 0e 00 00 49 8b 9c 24 c8 00 00 00 48 be 00 00
RSP: 0018:ffff8880959defc8 EFLAGS: 00010202
RAX: 0000000000000019 RBX: ffff888081258a48 RCX: dffffc0000000000
RDX: 0000000000000000 RSI: ffffffff86cab862 RDI: 00000000000000c8
RBP: ffff8880959df030 R08: ffff8880813d0200 R09: ffffed1015d05bc8
R10: ffffed1015d05bc7 R11: ffff8880ae82de3b R12: 0000000000000000
R13: 000000000000002c R14: 0000000000000000 R15: ffff888081258a48
FS:  000000000106a880(0000) GS:ffff8880ae800000(0000)
 knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020001cc0 CR3: 0000000094a20000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 tipc_sk_filter_rcv+0x182d/0x34f0 net/tipc/socket.c:2168
 tipc_sk_enqueue net/tipc/socket.c:2254 [inline]
 tipc_sk_rcv+0xc45/0x25a0 net/tipc/socket.c:2305
 tipc_sk_mcast_rcv+0x724/0x1020 net/tipc/socket.c:1209
 tipc_mcast_xmit+0x7fe/0x1200 net/tipc/bcast.c:410
 tipc_sendmcast+0xb36/0xfc0 net/tipc/socket.c:820
 __tipc_sendmsg+0x10df/0x18d0 net/tipc/socket.c:1358
 tipc_sendmsg+0x53/0x80 net/tipc/socket.c:1291
 sock_sendmsg_nosec net/socket.c:651 [inline]
 sock_sendmsg+0xdd/0x130 net/socket.c:661
 ___sys_sendmsg+0x806/0x930 net/socket.c:2260
 __sys_sendmsg+0x105/0x1d0 net/socket.c:2298
 __do_sys_sendmsg net/socket.c:2307 [inline]
 __se_sys_sendmsg net/socket.c:2305 [inline]
 __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2305
 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4401c9
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8
 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05
 <48> 3d 01 f0 ff ff 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffd887fa9d8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004401c9
RDX: 0000000000000000 RSI: 0000000020002140 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401a50
R13: 0000000000401ae0 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace ba79875754e1708f ]---

Reported-by: syzbot+be4bdf2cc3e85e952c50@syzkaller.appspotmail.com
Fixes: c55c8eda ("tipc: smooth change between replicast and broadcast")
Acked-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: Hoang Le <hoang.h.le@dektech.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/bcast.c

@@ -760,7 +760,7 @@ u32 tipc_bcast_get_broadcast_ratio(struct net *net)
 	return bb->rc_ratio;
 }
 
-void tipc_mcast_filter_msg(struct sk_buff_head *defq,
+void tipc_mcast_filter_msg(struct net *net, struct sk_buff_head *defq,
 			   struct sk_buff_head *inputq)
 {
 	struct sk_buff *skb, *_skb, *tmp;
@@ -775,6 +775,9 @@ void tipc_mcast_filter_msg(struct sk_buff_head *defq,
 		return;
 
 	node = msg_orignode(hdr);
+	if (node == tipc_own_addr(net))
+		return;
+
 	port = msg_origport(hdr);
 
 	/* Has the twin SYN message already arrived ? */

net/tipc/bcast.h

@@ -101,7 +101,7 @@ int tipc_bclink_reset_stats(struct net *net);
 u32 tipc_bcast_get_broadcast_mode(struct net *net);
 u32 tipc_bcast_get_broadcast_ratio(struct net *net);
 
-void tipc_mcast_filter_msg(struct sk_buff_head *defq,
+void tipc_mcast_filter_msg(struct net *net, struct sk_buff_head *defq,
 			   struct sk_buff_head *inputq);
 
 static inline void tipc_bcast_lock(struct net *net)

net/tipc/socket.c

@@ -2166,7 +2166,7 @@ static void tipc_sk_filter_rcv(struct sock *sk, struct sk_buff *skb,
 		tipc_group_filter_msg(grp, &inputq, xmitq);
 
 	if (unlikely(!grp) && mtyp == TIPC_MCAST_MSG)
-		tipc_mcast_filter_msg(&tsk->mc_method.deferredq, &inputq);
+		tipc_mcast_filter_msg(net, &tsk->mc_method.deferredq, &inputq);
 
 	/* Validate and add to receive buffer if there is space */
 	while ((skb = __skb_dequeue(&inputq))) {