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

net/ipv4/tcp_output.c +2 −1
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
1719	mss_now -= icsk->icsk_ext_hdr_len;	1719	mss_now -= icsk->icsk_ext_hdr_len;
1720		1720
1721	/* Then reserve room for full set of TCP options and 8 bytes of data */	1721	/* 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));
1723	return mss_now;	1724	return mss_now;
1724	}	1725	}
1725		1726

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
173	mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1;	173	mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1;
174	mss = min(READ_ONCE(net->ipv4.sysctl_tcp_base_mss), mss);	174	mss = min(READ_ONCE(net->ipv4.sysctl_tcp_base_mss), mss);
175	mss = max(mss, net->ipv4.sysctl_tcp_mtu_probe_floor);	175	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));
177	icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);	177	icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
178	}	178	}
179	tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);	179	tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);