[PATCH 4.14 112/115] net: sched: fix crash when deleting secondary chains

[Greg Kroah-Hartman]

4.14-stable review patch.  If anyone has any objections, please let me know.

--

From: Roman Kapl 

commit d7aa04a5e82b4f254d306926c81eae8df69e5200 upstream.

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 : 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 
Signed-off-by: Roman Kapl 
Signed-off-by: David S. Miller 
Cc: Cong Wang 
Signed-off-by: Greg Kroah-Hartman 

---
 net/sched/cls_api.c |7 ---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -197,14 +197,15 @@ static struct tcf_chain *tcf_chain_creat
 
 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);
}
 }
 

[PATCH 4.14 112/115] net: sched: fix crash when deleting secondary chains

[Greg Kroah-Hartman]

4.14-stable review patch.  If anyone has any objections, please let me know.

--

From: Roman Kapl 

commit d7aa04a5e82b4f254d306926c81eae8df69e5200 upstream.

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 : 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 
Signed-off-by: Roman Kapl 
Signed-off-by: David S. Miller 
Cc: Cong Wang 
Signed-off-by: Greg Kroah-Hartman 

---
 net/sched/cls_api.c |7 ---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -197,14 +197,15 @@ static struct tcf_chain *tcf_chain_creat
 
 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);
}
 }