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From:   Tommi Rantala <tommi.t.rantala@nokia.com>
To:     Jon Maloy <jon.maloy@ericsson.com>,
        Ying Xue <ying.xue@windriver.com>,
        "David S. Miller" <davem@davemloft.net>, netdev@vger.kernel.org,
        tipc-discussion@lists.sourceforge.net, linux-kernel@vger.kernel.org
Cc:     Tommi Rantala <tommi.t.rantala@nokia.com>
Subject: [PATCH] tipc: call tipc_rcv() only if bearer is up in tipc_udp_recv()
Date:   Tue, 28 Nov 2017 14:53:15 +0200
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Call tipc_rcv() only if bearer is up in tipc_udp_recv().
Fixes a rare TIPC div-by-zero crash in tipc_node_calculate_timer():

We're enabling a bearer, but it's not yet up and fully initialized.
At the same time we receive a discovery packet, and in tipc_udp_recv()
we end up calling tipc_rcv() with the not-yet-initialized bearer,
causing later a div-by-zero crash in tipc_node_calculate_timer().

[   12.590450] Own node address <1.1.1>, network identity 1
[   12.668088] divide error: 0000 [#1] SMP
[   12.676952] CPU: 2 PID: 0 Comm: swapper/2 Not tainted 4.14.2-dirty #1
[   12.679225] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-2.fc27 04/01/2014
[   12.682095] task: ffff8c2a761edb80 task.stack: ffffa41cc0cac000
[   12.684087] RIP: 0010:tipc_node_calculate_timer.isra.12+0x45/0x60 [tipc]
[   12.686486] RSP: 0018:ffff8c2a7fc838a0 EFLAGS: 00010246
[   12.688451] RAX: 0000000000000000 RBX: ffff8c2a5b382600 RCX: 0000000000000000
[   12.691197] RDX: 0000000000000000 RSI: ffff8c2a5b382600 RDI: ffff8c2a5b382600
[   12.693945] RBP: ffff8c2a7fc838b0 R08: 0000000000000001 R09: 0000000000000001
[   12.696632] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8c2a5d8949d8
[   12.699491] R13: ffffffff95ede400 R14: 0000000000000000 R15: ffff8c2a5d894800
[   12.702338] FS:  0000000000000000(0000) GS:ffff8c2a7fc80000(0000) knlGS:0000000000000000
[   12.705099] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   12.706776] CR2: 0000000001bb9440 CR3: 00000000bd009001 CR4: 00000000003606e0
[   12.708847] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   12.711016] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   12.712627] Call Trace:
[   12.713390]  <IRQ>
[   12.714011]  tipc_node_check_dest+0x2e8/0x350 [tipc]
[   12.715286]  tipc_disc_rcv+0x14d/0x1d0 [tipc]
[   12.716370]  tipc_rcv+0x8b0/0xd40 [tipc]
[   12.717396]  ? minmax_running_min+0x2f/0x60
[   12.718248]  ? dst_alloc+0x4c/0xa0
[   12.718964]  ? tcp_ack+0xaf1/0x10b0
[   12.719658]  ? tipc_udp_is_known_peer+0xa0/0xa0 [tipc]
[   12.720634]  tipc_udp_recv+0x71/0x1d0 [tipc]
[   12.721459]  ? dst_alloc+0x4c/0xa0
[   12.722130]  udp_queue_rcv_skb+0x264/0x490
[   12.722924]  __udp4_lib_rcv+0x21e/0x990
[   12.723670]  ? ip_route_input_rcu+0x2dd/0xbf0
[   12.724442]  ? tcp_v4_rcv+0x958/0xa40
[   12.725039]  udp_rcv+0x1a/0x20
[   12.725587]  ip_local_deliver_finish+0x97/0x1d0
[   12.726323]  ip_local_deliver+0xaf/0xc0
[   12.726959]  ? ip_route_input_noref+0x19/0x20
[   12.727689]  ip_rcv_finish+0xdd/0x3b0
[   12.728307]  ip_rcv+0x2ac/0x360
[   12.728839]  __netif_receive_skb_core+0x6fb/0xa90
[   12.729580]  ? udp4_gro_receive+0x1a7/0x2c0
[   12.730274]  __netif_receive_skb+0x1d/0x60
[   12.730953]  ? __netif_receive_skb+0x1d/0x60
[   12.731637]  netif_receive_skb_internal+0x37/0xd0
[   12.732371]  napi_gro_receive+0xc7/0xf0
[   12.732920]  receive_buf+0x3c3/0xd40
[   12.733441]  virtnet_poll+0xb1/0x250
[   12.733944]  net_rx_action+0x23e/0x370
[   12.734476]  __do_softirq+0xc5/0x2f8
[   12.734922]  irq_exit+0xfa/0x100
[   12.735315]  do_IRQ+0x4f/0xd0
[   12.735680]  common_interrupt+0xa2/0xa2
[   12.736126]  </IRQ>
[   12.736416] RIP: 0010:native_safe_halt+0x6/0x10
[   12.736925] RSP: 0018:ffffa41cc0cafe90 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff4d
[   12.737756] RAX: 0000000000000000 RBX: ffff8c2a761edb80 RCX: 0000000000000000
[   12.738504] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
[   12.739258] RBP: ffffa41cc0cafe90 R08: 0000014b5b9795e5 R09: ffffa41cc12c7e88
[   12.740118] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000002
[   12.740964] R13: ffff8c2a761edb80 R14: 0000000000000000 R15: 0000000000000000
[   12.741831]  default_idle+0x2a/0x100
[   12.742323]  arch_cpu_idle+0xf/0x20
[   12.742796]  default_idle_call+0x28/0x40
[   12.743312]  do_idle+0x179/0x1f0
[   12.743761]  cpu_startup_entry+0x1d/0x20
[   12.744291]  start_secondary+0x112/0x120
[   12.744816]  secondary_startup_64+0xa5/0xa5
[   12.745367] Code: b9 f4 01 00 00 48 89 c2 48 c1 ea 02 48 3d d3 07 00
00 48 0f 47 d1 49 8b 0c 24 48 39 d1 76 07 49 89 14 24 48 89 d1 31 d2 48
89 df <48> f7 f1 89 c6 e8 81 6e ff ff 5b 41 5c 5d c3 66 90 66 2e 0f 1f
[   12.747527] RIP: tipc_node_calculate_timer.isra.12+0x45/0x60 [tipc] RSP: ffff8c2a7fc838a0
[   12.748555] ---[ end trace 1399ab83390650fd ]---
[   12.749296] Kernel panic - not syncing: Fatal exception in interrupt
[   12.750123] Kernel Offset: 0x13200000 from 0xffffffff82000000
(relocation range: 0xffffffff80000000-0xffffffffbfffffff)
[   12.751215] Rebooting in 60 seconds..

Fixes: c9b64d492b1f ("tipc: add replicast peer discovery")
Signed-off-by: Tommi Rantala <tommi.t.rantala@nokia.com>
---
 net/tipc/udp_media.c | 29 +++++++----------------------
 1 file changed, 7 insertions(+), 22 deletions(-)

diff --git a/net/tipc/udp_media.c b/net/tipc/udp_media.c
index ecca64fc6a6f..599e7be92024 100644
--- a/net/tipc/udp_media.c
+++ b/net/tipc/udp_media.c
@@ -344,42 +344,27 @@ static int tipc_udp_recv(struct sock *sk, struct sk_buff *skb)
 	struct udp_bearer *ub;
 	struct tipc_bearer *b;
 	struct tipc_msg *hdr;
-	int err;
 
 	ub = rcu_dereference_sk_user_data(sk);
 	if (!ub) {
 		pr_err_ratelimited("Failed to get UDP bearer reference");
-		goto out;
+		kfree_skb(skb);
+		return 0;
 	}
 	skb_pull(skb, sizeof(struct udphdr));
 	hdr = buf_msg(skb);
 
 	rcu_read_lock();
 	b = rcu_dereference_rtnl(ub->bearer);
-	if (!b)
-		goto rcu_out;
-
-	if (b && test_bit(0, &b->up)) {
+	if (likely(b && test_bit(0, &b->up))) {
 		tipc_rcv(sock_net(sk), skb, b);
-		rcu_read_unlock();
-		return 0;
-	}
-
-	if (unlikely(msg_user(hdr) == LINK_CONFIG)) {
-		err = tipc_udp_rcast_disc(b, skb);
-		if (err)
-			goto rcu_out;
+	} else {
+		if (unlikely(b && msg_user(hdr) == LINK_CONFIG))
+			tipc_udp_rcast_disc(b, skb);
+		kfree_skb(skb);
 	}
-
-	tipc_rcv(sock_net(sk), skb, b);
 	rcu_read_unlock();
 	return 0;
-
-rcu_out:
-	rcu_read_unlock();
-out:
-	kfree_skb(skb);
-	return 0;
 }
 
 static int enable_mcast(struct udp_bearer *ub, struct udp_media_addr *remote)
-- 
2.14.3


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