[PATCH 5.4 37/87] tcp: Fix data-races around sysctl_max_syn_backlog.
From: Greg Kroah-Hartman
Date: Wed Jul 27 2022 - 12:40:51 EST
From: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
[ Upstream commit 79539f34743d3e14cc1fa6577d326a82cc64d62f ]
While reading sysctl_max_syn_backlog, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its readers.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
net/ipv4/tcp_input.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index fbdb5de29a97..c1f26603cd2c 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6676,10 +6676,12 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
goto drop_and_free;
if (!want_cookie && !isn) {
+ int max_syn_backlog = READ_ONCE(net->ipv4.sysctl_max_syn_backlog);
+
/* Kill the following clause, if you dislike this way. */
if (!syncookies &&
- (net->ipv4.sysctl_max_syn_backlog - inet_csk_reqsk_queue_len(sk) <
- (net->ipv4.sysctl_max_syn_backlog >> 2)) &&
+ (max_syn_backlog - inet_csk_reqsk_queue_len(sk) <
+ (max_syn_backlog >> 2)) &&
!tcp_peer_is_proven(req, dst)) {
/* Without syncookies last quarter of
* backlog is filled with destinations,
--
2.35.1