tcp: Fix data-races around sysctl_tcp_max_reordering.

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

Fixes: dca145ffaa8d ("tcp: allow for bigger reordering level")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 31a9d2b..07dbcba 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1051,7 +1051,7 @@ static void tcp_check_sack_reordering(struct sock *sk, const u32 low_seq,
                         tp->undo_marker ? tp->undo_retrans : 0);
 #endif
                tp->reordering = min_t(u32, (metric + mss - 1) / mss,
-                                      sock_net(sk)->ipv4.sysctl_tcp_max_reordering);
+                                      READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_max_reordering));
        }
 
        /* This exciting event is worth to be remembered. 8) */
@@ -2030,7 +2030,7 @@ static void tcp_check_reno_reordering(struct sock *sk, const int addend)
                return;
 
        tp->reordering = min_t(u32, tp->packets_out + addend,
-                              sock_net(sk)->ipv4.sysctl_tcp_max_reordering);
+                              READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_max_reordering));
        tp->reord_seen++;
        NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRENOREORDER);
 }