From: Eric Dumazet <edumazet@google.com>
Date: Mon, 11 Dec 2017 01:55:02 +0000 (-0800)
Subject: tcp: do not overshoot window_clamp in tcp_rcv_space_adjust()
X-Git-Tag: v3.18.114~49
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c4005b74d9f68eda1fc83fbe0bd63c6b93fe020a;p=thirdparty%2Fkernel%2Fstable.git

tcp: do not overshoot window_clamp in tcp_rcv_space_adjust()

commit 02db55718d53f9d426cee504c27fb768e9ed4ffe upstream.

While rcvbuf is properly clamped by tcp_rmem[2], rcvwin
is left to a potentially too big value.

It has no serious effect, since :
1) tcp_grow_window() has very strict checks.
2) window_clamp can be mangled by user space to any value anyway.

tcp_init_buffer_space() and companions use tcp_full_space(),
we use tcp_win_from_space() to avoid reloading sk->sk_rcvbuf

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Wei Wang <weiwan@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: Benjamin Gilbert <benjamin.gilbert@coreos.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 556e232359374..69b958aa72001 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -605,7 +605,7 @@ void tcp_rcv_space_adjust(struct sock *sk)
 			sk->sk_rcvbuf = rcvbuf;
 
 			/* Make the window clamp follow along.  */
-			tp->window_clamp = rcvwin;
+			tp->window_clamp = tcp_win_from_space(rcvbuf);
 		}
 	}
 	tp->rcvq_space.space = copied;