tcp: Fix a data-race around sysctl_tcp_min_tso_segs.

While reading sysctl_tcp_min_tso_segs, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its reader.

Fixes: 6249207108ef ("tcp: TSO packets automatic sizing")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 80c9bed733372779431c482ad9b65f155588deca..6e29cf391a645d0fb5c2ce94d36f27422dba3cb7 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1995,7 +1995,7 @@ static u32 tcp_tso_segs(struct sock *sk, unsigned int mss_now)
 
        min_tso = ca_ops->min_tso_segs ?
                        ca_ops->min_tso_segs(sk) :
-                       sock_net(sk)->ipv4.sysctl_tcp_min_tso_segs;
+                       READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_min_tso_segs);
 
        tso_segs = tcp_tso_autosize(sk, mss_now, min_tso);
        return min_t(u32, tso_segs, sk->sk_gso_max_segs);