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tcp: Fix data-races around sysctl_max_syn_backlog.

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[ Upstream commit 79539f3474 ]

While reading sysctl_max_syn_backlog, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its readers.

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Kuniyuki Iwashima 2022-07-15 10:17:53 -07:00 • committed by Greg Kroah-Hartman
commit b3ce32e33a
1 changed files with 4 additions and 2 deletions
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6
net/ipv4/tcp_input.c
View file

@ -6847,10 +6847,12 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
goto drop_and_free; goto drop_and_free;
if (!want_cookie && !isn) { 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. */ /* Kill the following clause, if you dislike this way. */
if (!syncookies && if (!syncookies &&
(net->ipv4.sysctl_max_syn_backlog - inet_csk_reqsk_queue_len(sk) < (max_syn_backlog - inet_csk_reqsk_queue_len(sk) <
(net->ipv4.sysctl_max_syn_backlog >> 2)) && (max_syn_backlog >> 2)) &&
!tcp_peer_is_proven(req, dst)) { !tcp_peer_is_proven(req, dst)) {
/* Without syncookies last quarter of /* Without syncookies last quarter of
* backlog is filled with destinations, * backlog is filled with destinations,