tcp: Fix a data-race around sysctl_tcp_comp_sack_nr.

q2ven · davem330 · commit 79f55473bfc8 · 2022-07-25T12:42:10.000+01:00
While reading sysctl_tcp_comp_sack_nr, it can be changed concurrently. Thus, we need to add READ_ONCE() to its reader. Fixes: 9c21d2f ("tcp: add tcp_comp_sack_nr sysctl") Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
@@ -5521,7 +5521,7 @@ static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
 	}
 
 	if (!tcp_is_sack(tp) ||
-	    tp->compressed_ack >= sock_net(sk)->ipv4.sysctl_tcp_comp_sack_nr)
+	    tp->compressed_ack >= READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_comp_sack_nr))
 		goto send_now;
 
 	if (tp->compressed_ack_rcv_nxt != tp->rcv_nxt) {

Original file line number	Diff line number	Diff line change
`@@ -5521,7 +5521,7 @@ static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)`
`5521`	`5521`	`}`
`5522`	`5522`
`5523`	`5523`	`if (!tcp_is_sack(tp) \|\|`
`5524`		`- tp->compressed_ack >= sock_net(sk)->ipv4.sysctl_tcp_comp_sack_nr)`
	`5524`	`+ tp->compressed_ack >= READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_comp_sack_nr))`
`5525`	`5525`	`goto send_now;`
`5526`	`5526`
`5527`	`5527`	`if (tp->compressed_ack_rcv_nxt != tp->rcv_nxt) {`