From: Roman Kapl <code@xxxxxxxx>
[ Upstream commit d7aa04a5e82b4f254d306926c81eae8df69e5200 ]
If you flush (delete) a filter chain other than chain 0 (such as when
deleting the device), the kernel may run into a use-after-free. The
chain refcount must not be decremented unless we are sure we are done
with the chain.
To reproduce the bug, run:
ip link add dtest type dummy
tc qdisc add dev dtest ingress
tc filter add dev dtest chain 1 parent ffff: flower
ip link del dtest
Introduced in: commit f93e1cdcf42c ("net/sched: fix filter flushing"),
but unless you have KAsan or luck, you won't notice it until
commit 0dadc117ac8b ("cls_flower: use tcf_exts_get_net() before call_rcu()")
Fixes: f93e1cdcf42c ("net/sched: fix filter flushing")
Acked-by: Jiri Pirko <jiri@xxxxxxxxxxxx>
Signed-off-by: Roman Kapl <code@xxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
---
net/sched/cls_api.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index ecbb019efcbd..1451a56a8f93 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -197,14 +197,15 @@ static struct tcf_chain *tcf_chain_create(struct tcf_block *block,
static void tcf_chain_flush(struct tcf_chain *chain)
{
- struct tcf_proto *tp;
+ struct tcf_proto *tp = rtnl_dereference(chain->filter_chain);
if (chain->p_filter_chain)
RCU_INIT_POINTER(*chain->p_filter_chain, NULL);
- while ((tp = rtnl_dereference(chain->filter_chain)) != NULL) {
+ while (tp) {
RCU_INIT_POINTER(chain->filter_chain, tp->next);
- tcf_chain_put(chain);
tcf_proto_destroy(tp);
+ tp = rtnl_dereference(chain->filter_chain);
+ tcf_chain_put(chain);
}
}
--
2.13.0