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net: sched: fix use-after-free in tcf_action_destroy and tcf_del_walker

PATCH Applied Jiri Pirko 2 participants 4 messages Sep 13, 2017

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Jiri Pirko

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#0 lore raw

PATCH 1/1 net: sched: fix use-after-free in tcf_action_destroy and tcf_del_walker

From: Jiri Pirko <[email protected]>

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 <[email protected]>
---
 net/sched/act_api.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
net/sched/act_api.c +4 -2
index fcd7dc7..da6fa82 100644
@@ -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;
 	}
Signature · 1 line
2.9.3
maintainer Applied
#1 lore raw

From: Jiri Pirko <[email protected]>
Date: Wed, 13 Sep 2017 17:32:37 +0200

Quoted 11 lines

From: Jiri Pirko <[email protected]>

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:

Quoted 7 lines
[   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 <[email protected]>

Applied, thanks Jiri.

author maintainer
#2 lore raw
Quoted 17 lines · Wed, Sep 13, 2017 at 06:34:28PM CEST, [email protected] wrote:

From: Jiri Pirko <[email protected]>
Date: Wed, 13 Sep 2017 17:32:37 +0200

Quoted 14 lines

From: Jiri Pirko <[email protected]>

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
Quoted 6 lines
Quoted 4 lines

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 <[email protected]>

Applied, thanks Jiri.

Oh, I forgot to mention, this would be nice to push to stable.

maintainer
#3 lore raw

From: Jiri Pirko <[email protected]>
Date: Wed, 13 Sep 2017 22:50:06 +0200

Quoted 18 lines
Quoted 17 lines · Wed, Sep 13, 2017 at 06:34:28PM CEST, [email protected] wrote:

From: Jiri Pirko <[email protected]>
Date: Wed, 13 Sep 2017 17:32:37 +0200

Quoted 14 lines

From: Jiri Pirko <[email protected]>

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
Quoted 8 lines
Quoted 6 lines
Quoted 4 lines

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 <[email protected]>

Applied, thanks Jiri.

Oh, I forgot to mention, this would be nice to push to stable.

Ok, queued up.