tcp: Fix a data-race around sysctl_tcp_comp_sack_nr.

Guillaume Nault · Guillaume Nault · commit e1b28db51589 · 2023-01-17T12:25:15.000+01:00
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2160073 Upstream Status: linux.git commit 79f5547 Author: Kuniyuki Iwashima <kuniyu@amazon.com> Date: Fri Jul 22 11:22:03 2022 -0700 tcp: Fix a data-race around sysctl_tcp_comp_sack_nr. 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> Signed-off-by: Guillaume Nault <gnault@redhat.com>
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
@@ -5478,7 +5478,7 @@ 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
`@@ -5478,7 +5478,7 @@ static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)`
`5478`	`5478`	`}`
`5479`	`5479`
`5480`	`5480`	`if (!tcp_is_sack(tp) \|\|`
`5481`		`- tp->compressed_ack >= sock_net(sk)->ipv4.sysctl_tcp_comp_sack_nr)`
	`5481`	`+ tp->compressed_ack >= READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_comp_sack_nr))`
`5482`	`5482`	`goto send_now;`
`5483`	`5483`
`5484`	`5484`	`if (tp->compressed_ack_rcv_nxt != tp->rcv_nxt) {`