From 88d78bc097cd8ebc6541e93316c9d9bf651b13e8 Mon Sep 17 00:00:00 2001 From: Kuniyuki Iwashima Date: Wed, 13 Jul 2022 13:52:01 -0700 Subject: [PATCH] tcp: Fix data-races around sysctl_tcp_base_mss. While reading sysctl_tcp_base_mss, it can be changed concurrently. Thus, we need to add READ_ONCE() to its readers. Fixes: 5d424d5a674f ("[TCP]: MTU probing") Signed-off-by: Kuniyuki Iwashima Signed-off-by: David S. Miller --- net/ipv4/tcp_output.c | 2 +- net/ipv4/tcp_timer.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 3fcfc0f1e9f9..9450d8469871 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -1765,7 +1765,7 @@ 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; diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c index 98bb00e29e1e..04063c7e33ba 100644 --- a/net/ipv4/tcp_timer.c +++ b/net/ipv4/tcp_timer.c @@ -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);