linux-kernel - [PATCH] net: Update window_clamp if SOCK

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:   Mon,  9 Nov 2020 17:20:14 +0800
From:   Mao Wenan <wenan.mao@...ux.alibaba.com>
To:     edumazet@...gle.com, davem@...emloft.net, kuznet@....inr.ac.ru,
        yoshfuji@...ux-ipv6.org, kuba@...nel.org
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org,
        Mao Wenan <wenan.mao@...ux.alibaba.com>
Subject: [PATCH] net: Update window_clamp if SOCK_RCVBUF is set

When net.ipv4.tcp_syncookies=1 and syn flood is happened,
cookie_v4_check tries to redo what tcp_v4_send_synack did,
rsk_window_clamp will be changed if SOCK_RCVBUF is set
by user, which will make rcv_wscale is different, the client
still operates with initial window scale and can overshot
granted window, the client use the initial scale but local
server use new scale to advertise window value, and session
work abnormally.

Signed-off-by: Mao Wenan <wenan.mao@...ux.alibaba.com>
---
 net/ipv4/syncookies.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 6ac473b..57ce317 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -427,6 +427,10 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 
 	/* Try to redo what tcp_v4_send_synack did. */
 	req->rsk_window_clamp = tp->window_clamp ? :dst_metric(&rt->dst, RTAX_WINDOW);
+	/* limit the window selection if the user enforce a smaller rx buffer */
+	if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
+	    (req->rsk_window_clamp > tcp_full_space(sk) || req->rsk_window_clamp == 0))
+		req->rsk_window_clamp = tcp_full_space(sk);
 
 	tcp_select_initial_window(sk, tcp_full_space(sk), req->mss,
 				  &req->rsk_rcv_wnd, &req->rsk_window_clamp,
-- 
1.8.3.1