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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: 5f3e2bf008 ("tcp: add tcp_min_snd_mss sysctl")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Kuniyuki Iwashima 2022-07-13 13:52:02 -07:00 committed by David S. Miller
parent 88d78bc097
commit 78eb166cde
2 changed files with 3 additions and 2 deletions
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3
net/ipv4/tcp_output.c
View File

@ -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;
}

2
net/ipv4/tcp_timer.c
View File

@ -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);