Commit 78eb166c authored by Kuniyuki Iwashima's avatar Kuniyuki Iwashima Committed by David S. Miller
Browse files

tcp: Fix data-races around sysctl_tcp_min_snd_mss. 



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

Fixes: 5f3e2bf0 ("tcp: add tcp_min_snd_mss sysctl")
Signed-off-by: default avatarKuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 88d78bc0

net/ipv4/tcp_output.c

+2 −1
Original line number Diff line number Diff line
@@ -1719,7 +1719,8 @@ static inline int __tcp_mtu_to_mss(struct sock *sk, int pmtu) 
	mss_now -= icsk->icsk_ext_hdr_len;



	/* Then reserve room for full set of TCP options and 8 bytes of data */

	mss_now = max(mss_now, sock_net(sk)->ipv4.sysctl_tcp_min_snd_mss);

	mss_now = max(mss_now,

		      READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_min_snd_mss));

	return mss_now;

}

net/ipv4/tcp_timer.c

+1 −1
Original line number Diff line number Diff line
@@ -173,7 +173,7 @@ static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk) 
		mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1;

		mss = min(READ_ONCE(net->ipv4.sysctl_tcp_base_mss), mss);

		mss = max(mss, net->ipv4.sysctl_tcp_mtu_probe_floor);

		mss = max(mss, net->ipv4.sysctl_tcp_min_snd_mss);

		mss = max(mss, READ_ONCE(net->ipv4.sysctl_tcp_min_snd_mss));

		icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);

	}

	tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);