path: root/net/sched/cls_cgroup.c
diff options
authorWANG Cong <xiyou.wangcong@gmail.com>2017-04-19 14:21:21 -0700
committerDavid S. Miller <davem@davemloft.net>2017-04-21 13:58:15 -0400
commit763dbf6328e41de7a55851baf5ee49e367552531 (patch)
tree22138b66b3576d4368ba99c3ea1b9c88fb1bdeaa /net/sched/cls_cgroup.c
parentbpf: add napi_id read access to __sk_buff (diff)
net_sched: move the empty tp check from ->destroy() to ->delete()
We could have a race condition where in ->classify() path we dereference tp->root and meanwhile a parallel ->destroy() makes it a NULL. Daniel cured this bug in commit d936377414fa ("net, sched: respect rcu grace period on cls destruction"). This happens when ->destroy() is called for deleting a filter to check if we are the last one in tp, this tp is still linked and visible at that time. The root cause of this problem is the semantic of ->destroy(), it does two things (for non-force case): 1) check if tp is empty 2) if tp is empty we could really destroy it and its caller, if cares, needs to check its return value to see if it is really destroyed. Therefore we can't unlink tp unless we know it is empty. As suggested by Daniel, we could actually move the test logic to ->delete() so that we can safely unlink tp after ->delete() tells us the last one is just deleted and before ->destroy(). Fixes: 1e052be69d04 ("net_sched: destroy proto tp when all filters are gone") Cc: Roi Dayan <roid@mellanox.com> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: John Fastabend <john.fastabend@gmail.com> Cc: Jamal Hadi Salim <jhs@mojatatu.com> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sched/cls_cgroup.c')
1 files changed, 2 insertions, 6 deletions
diff --git a/net/sched/cls_cgroup.c b/net/sched/cls_cgroup.c
index b5e7c1bee6c3..12ce547eea04 100644
--- a/net/sched/cls_cgroup.c
+++ b/net/sched/cls_cgroup.c
@@ -131,20 +131,16 @@ errout:
return err;
-static bool cls_cgroup_destroy(struct tcf_proto *tp, bool force)
+static void cls_cgroup_destroy(struct tcf_proto *tp)
struct cls_cgroup_head *head = rtnl_dereference(tp->root);
- if (!force)
- return false;
/* Head can still be NULL due to cls_cgroup_init(). */
if (head)
call_rcu(&head->rcu, cls_cgroup_destroy_rcu);
- return true;
-static int cls_cgroup_delete(struct tcf_proto *tp, unsigned long arg)
+static int cls_cgroup_delete(struct tcf_proto *tp, unsigned long arg, bool *last)