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Eric Dumazet authored
commit e62a123b upstream. Neal reported crashes with this stack trace : RIP: 0010:[<ffffffff8c57231b>] tcp_v4_send_ack+0x41/0x20f ... CR2: 0000000000000018 CR3: 000000044005c000 CR4: 00000000001427e0 ... [<ffffffff8c57258e>] tcp_v4_reqsk_send_ack+0xa5/0xb4 [<ffffffff8c1a7caa>] tcp_check_req+0x2ea/0x3e0 [<ffffffff8c19e420>] tcp_rcv_state_process+0x850/0x2500 [<ffffffff8c1a6d21>] tcp_v4_do_rcv+0x141/0x330 [<ffffffff8c56cdb2>] sk_backlog_rcv+0x21/0x30 [<ffffffff8c098bbd>] tcp_recvmsg+0x75d/0xf90 [<ffffffff8c0a8700>] inet_recvmsg+0x80/0xa0 [<ffffffff8c17623e>] sock_aio_read+0xee/0x110 [<ffffffff8c066fcf>] do_sync_read+0x6f/0xa0 [<ffffffff8c0673a1>] SyS_read+0x1e1/0x290 [<ffffffff8c5ca262>] system_call_fastpath+0x16/0x1b The problem here is the skb we provide to tcp_v4_send_ack() had to be parked in the backlog of a new TCP fastopen child because this child was owned by the user at the time an out of window packet arrived. Before queuing a packet, TCP has to set skb->dev to NULL as the device could disappear before packet is removed from the queue. Fix this issue by using the net pointer provided by the socket (being a timewait or a request socket). IPv6 is immune to the bug : tcp_v6_send_response() already gets the net pointer from the socket if provided. Fixes: 168a8f58 ("tcp: TCP Fast Open Server - main code path") Reported-by:
Neal Cardwell <ncardwell@google.com> Signed-off-by:
Eric Dumazet <edumazet@google.com> Cc: Jerry Chu <hkchu@google.com> Cc: Yuchung Cheng <ycheng@google.com> Acked-by:
Neal Cardwell <ncardwell@google.com> Signed-off-by:
David S. Miller <davem@davemloft.net> [ luis: backported to 3.16: adjusted context ] Signed-off-by:
Luis Henriques <luis.henriques@canonical.com> Signed-off-by:
Kamal Mostafa <kamal@canonical.com>
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