From: Eric Dumazet <edumazet@google.com>
Date: Thu, 19 Mar 2020 02:21:02 +0000 (-0700)
Subject: tcp: repair: fix TCP_QUEUE_SEQ implementation
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=6cd6cbf593bfa3ae6fc3ed34ac21da4d35045425;p=linux.git

tcp: repair: fix TCP_QUEUE_SEQ implementation

When application uses TCP_QUEUE_SEQ socket option to
change tp->rcv_next, we must also update tp->copied_seq.

Otherwise, stuff relying on tcp_inq() being precise can
eventually be confused.

For example, tcp_zerocopy_receive() might crash because
it does not expect tcp_recv_skb() to return NULL.

We could add tests in various places to fix the issue,
or simply make sure tcp_inq() wont return a random value,
and leave fast path as it is.

Note that this fixes ioctl(fd, SIOCINQ, &val) at the same
time.

Fixes: ee9952831cfd ("tcp: Initial repair mode")
Fixes: 05255b823a61 ("tcp: add TCP_ZEROCOPY_RECEIVE support for zerocopy receive")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index eb2d80519f8e5..dc77c303e6f7f 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2948,8 +2948,10 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
 			err = -EPERM;
 		else if (tp->repair_queue == TCP_SEND_QUEUE)
 			WRITE_ONCE(tp->write_seq, val);
-		else if (tp->repair_queue == TCP_RECV_QUEUE)
+		else if (tp->repair_queue == TCP_RECV_QUEUE) {
 			WRITE_ONCE(tp->rcv_nxt, val);
+			WRITE_ONCE(tp->copied_seq, val);
+		}
 		else
 			err = -EINVAL;
 		break;