net: sched: act_sample: fix psample group handling on overwrite

Action sample doesn't properly handle psample_group pointer in overwrite
case. Following issues need to be fixed:

- In tcf_sample_init() function RCU_INIT_POINTER() is used to set
  s->psample_group, even though we neither setting the pointer to NULL, nor
  preventing concurrent readers from accessing the pointer in some way.
  Use rcu_swap_protected() instead to safely reset the pointer.

- Old value of s->psample_group is not released or deallocated in any way,
  which results resource leak. Use psample_group_put() on non-NULL value
  obtained with rcu_swap_protected().

- The function psample_group_put() that released reference to struct
  psample_group pointed by rcu-pointer s->psample_group doesn't respect rcu
  grace period when deallocating it. Extend struct psample_group with rcu
  head and use kfree_rcu when freeing it.

Fixes: 5c5670fae430 ("net/sched: Introduce sample tc action")
Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 1 deletions

diff --git a/net/psample/psample.c b/net/psample/psample.c
index 841f198ea1a8..66e4b61a350d 100644
--- a/net/psample/psample.c
+++ b/net/psample/psample.c
@@ -154,7 +154,7 @@ static void psample_group_destroy(struct psample_group *group)
 {
 	psample_group_notify(group, PSAMPLE_CMD_DEL_GROUP);
 	list_del(&group->list);
-	kfree(group);
+	kfree_rcu(group, rcu);
 }
 
 static struct psample_group *