linux-kernel - [PATCH 3.18 37/85] tcp: do not overshoot window_clamp in tcp_rcv_space

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Date:   Sun,  1 Jul 2018 18:01:55 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
        Soheil Hassas Yeganeh <soheil@...gle.com>,
        Wei Wang <weiwan@...gle.com>,
        Neal Cardwell <ncardwell@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Benjamin Gilbert <benjamin.gilbert@...eos.com>,
        Guenter Roeck <linux@...ck-us.net>
Subject: [PATCH 3.18 37/85] tcp: do not overshoot window_clamp in tcp_rcv_space_adjust()

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@...gle.com>

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@...gle.com>
Acked-by: Soheil Hassas Yeganeh <soheil@...gle.com>
Acked-by: Wei Wang <weiwan@...gle.com>
Acked-by: Neal Cardwell <ncardwell@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Cc: Benjamin Gilbert <benjamin.gilbert@...eos.com>
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 net/ipv4/tcp_input.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -605,7 +605,7 @@ void tcp_rcv_space_adjust(struct sock *s
 			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;