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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.

Kuniyuki Iwashima committed 4 years ago

Commit 78eb1661 parent 88d78bc2 files · +3 −2Browse files

Unified · Split

2 files
  1. net/ipv4/tcp_output.c +2 −1
  2. net/ipv4/tcp_timer.c +1 −1
net/ipv4/tcp_output.c+2−1
@@ -1719,7 +1719,8 @@ static inline int __tcp_mtu_to_mss(struct sock *sk, int pmtu) · 1718 unmodified lines
17191719 mss_now -= icsk->icsk_ext_hdr_len;
17201720
17211721 /* Then reserve room for full set of TCP options and 8 bytes of data */
1722− mss_now = max(mss_now, sock_net(sk)->ipv4.sysctl_tcp_min_snd_mss);
1722+ mss_now = max(mss_now,
1723+ READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_min_snd_mss));
17231724 return mss_now;
17241725 }
17251726
net/ipv4/tcp_timer.c+1−1
@@ -173,7 +173,7 @@ static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk) · 172 unmodified lines
173173 mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1;
174174 mss = min(READ_ONCE(net->ipv4.sysctl_tcp_base_mss), mss);
175175 mss = max(mss, net->ipv4.sysctl_tcp_mtu_probe_floor);
176− mss = max(mss, net->ipv4.sysctl_tcp_min_snd_mss);
176+ mss = max(mss, READ_ONCE(net->ipv4.sysctl_tcp_min_snd_mss));
177177 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
178178 }
179179 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);