linux-kernel - [PATCH 4.19 14/17] udp: Copy has_conns in reuseport

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Message-Id: <20200730074421.161531583@linuxfoundation.org>
Date:   Thu, 30 Jul 2020 10:04:40 +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, Willem de Bruijn <willemb@...gle.com>,
        Benjamin Herrenschmidt <benh@...zon.com>,
        Kuniyuki Iwashima <kuniyu@...zon.co.jp>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.19 14/17] udp: Copy has_conns in reuseport_grow().

From: Kuniyuki Iwashima <kuniyu@...zon.co.jp>

[ Upstream commit f2b2c55e512879a05456eaf5de4d1ed2f7757509 ]

If an unconnected socket in a UDP reuseport group connect()s, has_conns is
set to 1. Then, when a packet is received, udp[46]_lib_lookup2() scans all
sockets in udp_hslot looking for the connected socket with the highest
score.

However, when the number of sockets bound to the port exceeds max_socks,
reuseport_grow() resets has_conns to 0. It can cause udp[46]_lib_lookup2()
to return without scanning all sockets, resulting in that packets sent to
connected sockets may be distributed to unconnected sockets.

Therefore, reuseport_grow() should copy has_conns.

Fixes: acdcecc61285 ("udp: correct reuseport selection with connected sockets")
CC: Willem de Bruijn <willemb@...gle.com>
Reviewed-by: Benjamin Herrenschmidt <benh@...zon.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.co.jp>
Acked-by: Willem de Bruijn <willemb@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/core/sock_reuseport.c |    1 +
 1 file changed, 1 insertion(+)

--- a/net/core/sock_reuseport.c
+++ b/net/core/sock_reuseport.c
@@ -112,6 +112,7 @@ static struct sock_reuseport *reuseport_
 	more_reuse->prog = reuse->prog;
 	more_reuse->reuseport_id = reuse->reuseport_id;
 	more_reuse->bind_inany = reuse->bind_inany;
+	more_reuse->has_conns = reuse->has_conns;
 
 	memcpy(more_reuse->socks, reuse->socks,
 	       reuse->num_socks * sizeof(struct sock *));