[PATCH 4.4 008/105] tcp: do not overshoot window_clamp in tcp_rcv_space_adjust()

From: Greg Kroah-Hartman
Date: Sun Jul 01 2018 - 14:32:48 EST

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


From: Eric Dumazet <edumazet@xxxxxxxxxx>

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@xxxxxxxxxx>
Acked-by: Soheil Hassas Yeganeh <soheil@xxxxxxxxxx>
Acked-by: Wei Wang <weiwan@xxxxxxxxxx>
Acked-by: Neal Cardwell <ncardwell@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Cc: Benjamin Gilbert <benjamin.gilbert@xxxxxxxxxx>
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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
@@ -612,7 +612,7 @@ 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;