1. 13 Aug, 2017 2 commits
    • Eric Dumazet's avatar
      net: fix keepalive code vs TCP_FASTOPEN_CONNECT · 52b0231e
      Eric Dumazet authored
      
      [ Upstream commit 2dda6400 ]
      
      syzkaller was able to trigger a divide by 0 in TCP stack [1]
      
      Issue here is that keepalive timer needs to be updated to not attempt
      to send a probe if the connection setup was deferred using
      TCP_FASTOPEN_CONNECT socket option added in linux-4.11
      
      [1]
       divide error: 0000 [#1] SMP
       CPU: 18 PID: 0 Comm: swapper/18 Not tainted
       task: ffff986f62f4b040 ti: ffff986f62fa2000 task.ti: ffff986f62fa2000
       RIP: 0010:[<ffffffff8409cc0d>]  [<ffffffff8409cc0d>] __tcp_select_window+0x8d/0x160
       Call Trace:
        <IRQ>
        [<ffffffff8409d951>] tcp_transmit_skb+0x11/0x20
        [<ffffffff8409da21>] tcp_xmit_probe_skb+0xc1/0xe0
        [<ffffffff840a0ee8>] tcp_write_wakeup+0x68/0x160
        [<ffffffff840a151b>] tcp_keepalive_timer+0x17b/0x230
        [<ffffffff83b3f799>] call_timer_fn+0x39/0xf0
        [<ffffffff83b40797>] run_timer_softirq+0x1d7/0x280
        [<ffffffff83a04ddb>] __do_softirq+0xcb/0x257
        [<ffffffff83ae03ac>] irq_exit+0x9c/0xb0
        [<ffffffff83a04c1a>] smp_apic_timer_interrupt+0x6a/0x80
        [<ffffffff83a03eaf>] apic_timer_interrupt+0x7f/0x90
        <EOI>
        [<ffffffff83fed2ea>] ? cpuidle_enter_state+0x13a/0x3b0
        [<ffffffff83fed2cd>] ? cpuidle_enter_state+0x11d/0x3b0
      
      Tested:
      
      Following packetdrill no longer crashes the kernel
      
      `echo 0 >/proc/sys/net/ipv4/tcp_timestamps`
      
      // Cache warmup: send a Fast Open cookie request
          0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
         +0 fcntl(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0
         +0 setsockopt(3, SOL_TCP, TCP_FASTOPEN_CONNECT, [1], 4) = 0
         +0 connect(3, ..., ...) = -1 EINPROGRESS (Operation is now in progress)
         +0 > S 0:0(0) <mss 1460,nop,nop,sackOK,nop,wscale 8,FO,nop,nop>
       +.01 < S. 123:123(0) ack 1 win 14600 <mss 1460,nop,nop,sackOK,nop,wscale 6,FO abcd1234,nop,nop>
         +0 > . 1:1(0) ack 1
         +0 close(3) = 0
         +0 > F. 1:1(0) ack 1
         +0 < F. 1:1(0) ack 2 win 92
         +0 > .  2:2(0) ack 2
      
         +0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 4
         +0 fcntl(4, F_SETFL, O_RDWR|O_NONBLOCK) = 0
         +0 setsockopt(4, SOL_TCP, TCP_FASTOPEN_CONNECT, [1], 4) = 0
         +0 setsockopt(4, SOL_SOCKET, SO_KEEPALIVE, [1], 4) = 0
       +.01 connect(4, ..., ...) = 0
         +0 setsockopt(4, SOL_TCP, TCP_KEEPIDLE, [5], 4) = 0
         +10 close(4) = 0
      
      `echo 1 >/proc/sys/net/ipv4/tcp_timestamps`
      
      Fixes: 19f6d3f3 ("net/tcp-fastopen: Add new API support")
      Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
      Reported-by: default avatarDmitry Vyukov <dvyukov@google.com>
      Cc: Wei Wang <weiwan@google.com>
      Cc: Yuchung Cheng <ycheng@google.com>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      52b0231e
    • Yuchung Cheng's avatar
      tcp: avoid setting cwnd to invalid ssthresh after cwnd reduction states · 0864b111
      Yuchung Cheng authored
      
      [ Upstream commit ed254971 ]
      
      If the sender switches the congestion control during ECN-triggered
      cwnd-reduction state (CA_CWR), upon exiting recovery cwnd is set to
      the ssthresh value calculated by the previous congestion control. If
      the previous congestion control is BBR that always keep ssthresh
      to TCP_INIFINITE_SSTHRESH, cwnd ends up being infinite. The safe
      step is to avoid assigning invalid ssthresh value when recovery ends.
      Signed-off-by: default avatarYuchung Cheng <ycheng@google.com>
      Signed-off-by: default avatarNeal Cardwell <ncardwell@google.com>
      Acked-by: default avatarEric Dumazet <edumazet@google.com>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      0864b111
  2. 11 Aug, 2017 38 commits