On 12/19/2017 03:24 PM, Kirill Tkhai wrote:
> It seems there was no synchronization since the time
> when ioctls in kernel were serialized via single mutex.
>
> Signed-off-by: Kirill Tkhai <ktk...@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);
It probably would be easier to simply use xchg() here. Locking wouldn't be
needed in that case.
But as I assume this is not performance sensitive code, so mutex should be fine.
Acked-by: Andrey Ryabinin <aryabi...@virtuozzo.com>
> }
> - rcu_read_unlock();
> + mutex_unlock(&info_mutex);
>
> synchronize_net();
> /* IMPORTANT. I think reset of statistics collected should not be
>
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