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Commit 30b73edc authored by Kuniyuki Iwashima's avatar Kuniyuki Iwashima Committed by Greg Kroah-Hartman
Browse files

tcp: Fix data-races around sysctl_tcp_base_mss. 



[ Upstream commit 88d78bc097cd8ebc6541e93316c9d9bf651b13e8 ]

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

Fixes: 5d424d5a ("[TCP]: MTU probing")
Signed-off-by: default avatarKuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent f966773e

net/ipv4/tcp_output.c

+1 −1
Original line number Diff line number Diff line
@@ -1540,7 +1540,7 @@ void tcp_mtup_init(struct sock *sk) 
	icsk->icsk_mtup.enabled = READ_ONCE(net->ipv4.sysctl_tcp_mtu_probing) > 1;

	icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +

			       icsk->icsk_af_ops->net_header_len;

	icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, net->ipv4.sysctl_tcp_base_mss);

	icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, READ_ONCE(net->ipv4.sysctl_tcp_base_mss));

	icsk->icsk_mtup.probe_size = 0;

	if (icsk->icsk_mtup.enabled)

		icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;

net/ipv4/tcp_timer.c

+1 −1
Original line number Diff line number Diff line
@@ -171,7 +171,7 @@ static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk) 
		icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;

	} else {

		mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1;

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

		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);

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