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Commit fdb96b69 authored by Kuniyuki Iwashima's avatar Kuniyuki Iwashima Committed by Greg Kroah-Hartman
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tcp: Fix data-races around sysctl_tcp_min_snd_mss. 



[ Upstream commit 78eb166cdefcc3221c8c7c1e2d514e91a2eb5014 ]

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>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 30b73edc

net/ipv4/tcp_output.c

+2 −1
Original line number Diff line number Diff line
@@ -1494,7 +1494,8 @@ 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);