Commit 12b8d9ca authored by Kuniyuki Iwashima's avatar Kuniyuki Iwashima Committed by David S. Miller
Browse files

tcp: Fix a data-race around sysctl_tcp_ecn_fallback. 



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

Fixes: 49213555 ("tcp: add rfc3168, section 6.1.1.1. fallback")
Signed-off-by: default avatarKuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 4785a667

net/ipv4/sysctl_net_ipv4.c

+2 −0
Original line number Diff line number Diff line
@@ -685,6 +685,8 @@ static struct ctl_table ipv4_net_table[] = { 
		.maxlen		= sizeof(u8),

		.mode		= 0644,

		.proc_handler	= proc_dou8vec_minmax,

		.extra1		= SYSCTL_ZERO,

		.extra2		= SYSCTL_ONE,

	},

	{

		.procname	= "ip_dynaddr",

net/ipv4/tcp_output.c

+1 −1
Original line number Diff line number Diff line
@@ -346,7 +346,7 @@ static void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb) 


static void tcp_ecn_clear_syn(struct sock *sk, struct sk_buff *skb)

{

	if (sock_net(sk)->ipv4.sysctl_tcp_ecn_fallback)

	if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_fallback))

		/* tp->ecn_flags are cleared at a later point in time when

		 * SYN ACK is ultimatively being received.

		 */