tcp: Fix a data-race around sysctl_max_tw_buckets.

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

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/inet_timewait_sock.c b/net/ipv4/inet_timewait_sock.c
index 0ec5018..47ccc34 100644 (file)
--- a/net/ipv4/inet_timewait_sock.c
+++ b/net/ipv4/inet_timewait_sock.c
@@ -156,7 +156,8 @@ struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk,
 {
        struct inet_timewait_sock *tw;
 
-       if (refcount_read(&dr->tw_refcount) - 1 >= dr->sysctl_max_tw_buckets)
+       if (refcount_read(&dr->tw_refcount) - 1 >=
+           READ_ONCE(dr->sysctl_max_tw_buckets))
                return NULL;
 
        tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab,