From 6508b6781be076f889e3077a1a5fadf1930a569d Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sat, 7 Jul 2018 23:00:01 -0700 Subject: [PATCH] tcp: cleanup copied_seq and urg_data in tcp_disconnect tcp_zerocopy_receive() relies on tcp_inq() to limit number of bytes requested by user. syzbot found that after tcp_disconnect(), tcp_inq() was returning a stale value (number of bytes in queue before the disconnect). Note that after this patch, ioctl(fd, SIOCINQ, &val) is also fixed and returns 0, so this might be a candidate for all known linux kernels. While we are at this, we probably also should clear urg_data to avoid other syzkaller reports after it discovers how to deal with urgent data. syzkaller repro : socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 3 bind(3, {sa_family=AF_INET, sin_port=htons(20000), sin_addr=inet_addr("224.0.0.1")}, 16) = 0 connect(3, {sa_family=AF_INET, sin_port=htons(20000), sin_addr=inet_addr("127.0.0.1")}, 16) = 0 send(3, ..., 4096, 0) = 4096 connect(3, {sa_family=AF_UNSPEC, sa_data="\0\0\0\0\0\0\0\0\0\0\0\0\0\0"}, 128) = 0 getsockopt(3, SOL_TCP, TCP_ZEROCOPY_RECEIVE, ..., [16]) = 0 // CRASH Fixes: 05255b823a61 ("tcp: add TCP_ZEROCOPY_RECEIVE support for zerocopy receive") Signed-off-by: Eric Dumazet Reported-by: syzbot Signed-off-by: David S. Miller --- net/ipv4/tcp.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index c959bb6..0d43705 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -2562,6 +2562,8 @@ int tcp_disconnect(struct sock *sk, int flags) tcp_clear_xmit_timers(sk); __skb_queue_purge(&sk->sk_receive_queue); + tp->copied_seq = tp->rcv_nxt; + tp->urg_data = 0; tcp_write_queue_purge(sk); tcp_fastopen_active_disable_ofo_check(sk); skb_rbtree_purge(&tp->out_of_order_queue); -- 2.7.4