[Devel] [PATCH 1/2] vznetstat: Add protection to venet_acct_set_classes()

[Kirill Tkhai]

It seems there was no synchronization since the time
when ioctls in kernel were serialized via single mutex.

Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
---
 kernel/ve/vznetstat/vznetstat.c |   11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/kernel/ve/vznetstat/vznetstat.c b/kernel/ve/vznetstat/vznetstat.c
index 3a53ce27bde2..a65e05378ff4 100644
--- a/kernel/ve/vznetstat/vznetstat.c
+++ b/kernel/ve/vznetstat/vznetstat.c
@@ -52,6 +52,7 @@ static struct class_info_set *info_v4 = NULL;
 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
 static struct class_info_set *info_v6 = NULL;
 #endif
+static DEFINE_MUTEX(info_mutex);
 
 /* v6: flag IPv6 classes or IPv4 */
 static int venet_acct_set_classes(const void __user *user_info, int length, int v6)
@@ -88,15 +89,17 @@ static int venet_acct_set_classes(const void __user *user_info, int length, int
 			goto out_free;
 	}
 
-	rcu_read_lock();
+	mutex_lock(&info_mutex);
 	if (v6) {
-		old = rcu_dereference(info_v6);
+		old = rcu_dereference_protected(info_v6,
+						lockdep_is_held(&info_mutex));
 		rcu_assign_pointer(info_v6, info);
 	} else {
-		old = rcu_dereference(info_v4);
+		old = rcu_dereference_protected(info_v4,
+						lockdep_is_held(&info_mutex));
 		rcu_assign_pointer(info_v4, info);
 	}
-	rcu_read_unlock();
+	mutex_unlock(&info_mutex);
 
 	synchronize_net();
 	/* IMPORTANT. I think reset of statistics collected should not be