[PATCH v1 net 09/16] tcp: Fix a data-race around sysctl_tcp_max_orphans.

[Kuniyuki Iwashima]

While reading sysctl_tcp_max_orphans, it can be changed concurrently.  So,
we need to add READ_ONCE().  Then we can set proc_dointvec_lockless() as
the handler to mark it safe.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
---
 net/ipv4/sysctl_net_ipv4.c | 2 +-
 net/ipv4/tcp.c             | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index cd448cdd3b38..aa5adf136556 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -476,7 +476,7 @@ static struct ctl_table ipv4_table[] = {
 		.data		= &sysctl_tcp_max_orphans,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec
+		.proc_handler	= proc_dointvec_lockless,
 	},
 	{
 		.procname	= "inet_peer_threshold",
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 028513d3e2a2..2222dfdde316 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2715,7 +2715,8 @@ static void tcp_orphan_update(struct timer_list *unused)
 
 static bool tcp_too_many_orphans(int shift)
 {
-	return READ_ONCE(tcp_orphan_cache) << shift > sysctl_tcp_max_orphans;
+	return READ_ONCE(tcp_orphan_cache) << shift >
+		READ_ONCE(sysctl_tcp_max_orphans);
 }
 
 bool tcp_check_oom(struct sock *sk, int shift)
-- 
2.30.2