path: root/net/sched/cls_route.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_route.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_route.c')
1 files changed, 15 insertions, 14 deletions
diff --git a/net/sched/cls_route.c b/net/sched/cls_route.c
index a371075c1d7a..f4d687e04240 100644
--- a/net/sched/cls_route.c
+++ b/net/sched/cls_route.c
@@ -276,20 +276,13 @@ static void route4_delete_filter(struct rcu_head *head)
-static bool route4_destroy(struct tcf_proto *tp, bool force)
+static void route4_destroy(struct tcf_proto *tp)
struct route4_head *head = rtnl_dereference(tp->root);
int h1, h2;
if (head == NULL)
- return true;
- if (!force) {
- for (h1 = 0; h1 <= 256; h1++) {
- if (rcu_access_pointer(head->table[h1]))
- return false;
- }
- }
+ return;
for (h1 = 0; h1 <= 256; h1++) {
struct route4_bucket *b;
@@ -314,10 +307,9 @@ static bool route4_destroy(struct tcf_proto *tp, bool force)
kfree_rcu(head, rcu);
- return true;
-static int route4_delete(struct tcf_proto *tp, unsigned long arg)
+static int route4_delete(struct tcf_proto *tp, unsigned long arg, bool *last)
struct route4_head *head = rtnl_dereference(tp->root);
struct route4_filter *f = (struct route4_filter *)arg;
@@ -325,7 +317,7 @@ static int route4_delete(struct tcf_proto *tp, unsigned long arg)
struct route4_filter *nf;
struct route4_bucket *b;
unsigned int h = 0;
- int i;
+ int i, h1;
if (!head || !f)
return -EINVAL;
@@ -356,16 +348,25 @@ static int route4_delete(struct tcf_proto *tp, unsigned long arg)
rt = rtnl_dereference(b->ht[i]);
if (rt)
- return 0;
+ goto out;
/* OK, session has no flows */
RCU_INIT_POINTER(head->table[to_hash(h)], NULL);
kfree_rcu(b, rcu);
+ break;
+ }
+ }
- return 0;
+ *last = true;
+ for (h1 = 0; h1 <= 256; h1++) {
+ if (rcu_access_pointer(head->table[h1])) {
+ *last = false;
+ break;
return 0;