[patch net] net: sched: fix use-after-free in tcf_action_destroy and tcf_del_walker
From: Jiri Pirko <jiri@resnulli.us>
Date: 2017-09-13 15:32:40
Subsystem:
networking [general], tc subsystem, the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Jamal Hadi Salim, Jiri Pirko, Linus Torvalds
From: Jiri Pirko <redacted>
Recent commit d7fb60b9cafb ("net_sched: get rid of tcfa_rcu") removed
freeing in call_rcu, which changed already existing hard-to-hit
race condition into 100% hit:
[ 598.599825] BUG: unable to handle kernel NULL pointer dereference at 0000000000000030
[ 598.607782] IP: tcf_action_destroy+0xc0/0x140
Or:
[ 40.858924] BUG: unable to handle kernel NULL pointer dereference at 0000000000000030
[ 40.862840] IP: tcf_generic_walker+0x534/0x820
Fix this by storing the ops and use them directly for module_put call.
Fixes: a85a970af265 ("net_sched: move tc_action into tcf_common")
Signed-off-by: Jiri Pirko <redacted>
---
net/sched/act_api.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index fcd7dc7..da6fa82 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c@@ -180,7 +180,7 @@ static int tcf_del_walker(struct tcf_idrinfo *idrinfo, struct sk_buff *skb, idr_for_each_entry_ext(idr, p, id) { ret = __tcf_idr_release(p, false, true); if (ret == ACT_P_DELETED) { - module_put(p->ops->owner); + module_put(ops->owner); n_i++; } else if (ret < 0) { goto nla_put_failure;
@@ -514,13 +514,15 @@ EXPORT_SYMBOL(tcf_action_exec); int tcf_action_destroy(struct list_head *actions, int bind) { + const struct tc_action_ops *ops; struct tc_action *a, *tmp; int ret = 0; list_for_each_entry_safe(a, tmp, actions, list) { + ops = a->ops; ret = __tcf_idr_release(a, bind, true); if (ret == ACT_P_DELETED) - module_put(a->ops->owner); + module_put(ops->owner); else if (ret < 0) return ret; }
--
2.9.3