tcp: Fix a data-race around sysctl_tcp_min_tso_segs.

BugLink: https://bugs.launchpad.net/bugs/1989218
[ Upstream commit e0bb4ab9dfddd872622239f49fb2bd403b70853b ]

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

Fixes: 95bd09eb2750 ("tcp: TSO packets automatic sizing")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 4389ad7e4c8ca1b220b614d067b0111eed9e5fe5..51f31311fdb67242ed0c7d5558adb2cebbf5075a 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1986,7 +1986,7 @@ 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);