Subject: [PATCH 27/38] udp: Copy has_conns in reuseport_grow().

From: Kuniyuki Iwashima <[email-masked]>
Date: Tue, 21 Jul 2020 15:15:30 +0900

[ 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 <[email-masked]>
Reviewed-by: Benjamin Herrenschmidt <[email-masked]>
Signed-off-by: Kuniyuki Iwashima <[email-masked]>
Acked-by: Willem de Bruijn <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 net/core/sock_reuseport.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/core/sock_reuseport.c b/net/core/sock_reuseport.c
index adcb3aea576d..bbdd3c7b6cb5 100644
--- a/net/core/sock_reuseport.c
+++ b/net/core/sock_reuseport.c
@@ -101,6 +101,7 @@ static struct sock_reuseport *reuseport_grow(struct sock_reuseport *reuse)
 	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 *));
-- 
2.26.2