Zhang Yanmin reported crashes [1] and provided a patch adding a synchronize_rcu() call in can_rx_unregister() The main problem seems that the sockets themselves are not RCU protected. If CAN uses RCU for delivery, then sockets should be freed only after one RCU grace period. Recent kernels could use sock_set_flag(sk, SOCK_RCU_FREE), but let's ease stable backports with the following fix instead. [1] BUG: unable to handle kernel NULL pointer dereference at (null) IP: [<ffffffff81495e25>] selinux_socket_sock_rcv_skb+0x65/0x2a0 Call Trace: <IRQ> [<ffffffff81485d8c>] security_sock_rcv_skb+0x4c/0x60 [<ffffffff81d55771>] sk_filter+0x41/0x210 [<ffffffff81d12913>] sock_queue_rcv_skb+0x53/0x3a0 [<ffffffff81f0a2b3>] raw_rcv+0x2a3/0x3c0 [<ffffffff81f06eab>] can_rcv_filter+0x12b/0x370 [<ffffffff81f07af9>] can_receive+0xd9/0x120 [<ffffffff81f07beb>] can_rcv+0xab/0x100 [<ffffffff81d362ac>] __netif_receive_skb_core+0xd8c/0x11f0 [<ffffffff81d36734>] __netif_receive_skb+0x24/0xb0 [<ffffffff81d37f67>] process_backlog+0x127/0x280 [<ffffffff81d36f7b>] net_rx_action+0x33b/0x4f0 [<ffffffff810c88d4>] __do_softirq+0x184/0x440 [<ffffffff81f9e86c>] do_softirq_own_stack+0x1c/0x30 <EOI> [<ffffffff810c76fb>] do_softirq.part.18+0x3b/0x40 [<ffffffff810c8bed>] do_softirq+0x1d/0x20 [<ffffffff81d30085>] netif_rx_ni+0xe5/0x110 [<ffffffff8199cc87>] slcan_receive_buf+0x507/0x520 [<ffffffff8167ef7c>] flush_to_ldisc+0x21c/0x230 [<ffffffff810e3baf>] process_one_work+0x24f/0x670 [<ffffffff810e44ed>] worker_thread+0x9d/0x6f0 [<ffffffff810e4450>] ? rescuer_thread+0x480/0x480 [<ffffffff810ebafc>] kthread+0x12c/0x150 [<ffffffff81f9ccef>] ret_from_fork+0x3f/0x70 Reported-by: Zhang Yanmin <yanmin.zhang@intel.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Acked-by: Oliver Hartkopp <socketcan@hartkopp.net> Signed-off-by: David S. Miller <davem@davemloft.net>