* [PATCH 2/2] l2tp: fix possible use-after-free
@ 2022-06-07 16:16 Xiaohui Zhang
2022-06-07 17:28 ` Eric Dumazet
0 siblings, 1 reply; 2+ messages in thread
From: Xiaohui Zhang @ 2022-06-07 16:16 UTC (permalink / raw)
To: Xiaohui Zhang, David S . Miller, Eric Dumazet, Jakub Kicinski,
Paolo Abeni, Xiyu Yang, Xin Tan, Xin Xiong, Tom Parkin, netdev,
linux-kernel
We detected a suspected bug with our code clone detection tool.
Similar to the handling of l2tp_tunnel_get in commit a622b40035d1
("l2ip: fix possible use-after-free"), we thought a patch might
be needed here as well.
Before taking a refcount on a rcu protected structure,
we need to make sure the refcount is not zero.
Signed-off-by: Xiaohui Zhang <xiaohuizhang@ruc.edu.cn>
---
net/l2tp/l2tp_core.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index b759fbd09b65..c5de6d4e0818 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -273,8 +273,8 @@ struct l2tp_session *l2tp_session_get(const struct net *net, u32 session_id)
rcu_read_lock_bh();
hlist_for_each_entry_rcu(session, session_list, global_hlist)
- if (session->session_id == session_id) {
- l2tp_session_inc_refcount(session);
+ if (session->session_id == session_id &&
+ refcount_inc_not_zero(&session->ref_count)) {
rcu_read_unlock_bh();
return session;
--
2.17.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH 2/2] l2tp: fix possible use-after-free
2022-06-07 16:16 [PATCH 2/2] l2tp: fix possible use-after-free Xiaohui Zhang
@ 2022-06-07 17:28 ` Eric Dumazet
0 siblings, 0 replies; 2+ messages in thread
From: Eric Dumazet @ 2022-06-07 17:28 UTC (permalink / raw)
To: Xiaohui Zhang
Cc: David S . Miller, Jakub Kicinski, Paolo Abeni, Xiyu Yang,
Xin Tan, Xin Xiong, Tom Parkin, netdev, LKML
On Tue, Jun 7, 2022 at 9:16 AM Xiaohui Zhang <xiaohuizhang@ruc.edu.cn> wrote:
>
> We detected a suspected bug with our code clone detection tool.
>
> Similar to the handling of l2tp_tunnel_get in commit a622b40035d1
> ("l2ip: fix possible use-after-free"), we thought a patch might
> be needed here as well.
>
> Before taking a refcount on a rcu protected structure,
> we need to make sure the refcount is not zero.
>
> Signed-off-by: Xiaohui Zhang <xiaohuizhang@ruc.edu.cn>
> ---
> net/l2tp/l2tp_core.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
> index b759fbd09b65..c5de6d4e0818 100644
> --- a/net/l2tp/l2tp_core.c
> +++ b/net/l2tp/l2tp_core.c
> @@ -273,8 +273,8 @@ struct l2tp_session *l2tp_session_get(const struct net *net, u32 session_id)
>
> rcu_read_lock_bh();
> hlist_for_each_entry_rcu(session, session_list, global_hlist)
> - if (session->session_id == session_id) {
> - l2tp_session_inc_refcount(session);
> + if (session->session_id == session_id &&
> + refcount_inc_not_zero(&session->ref_count)) {
> rcu_read_unlock_bh();
>
> return session;
> --
> 2.17.1
>
Please fix all bugs in a single patch.
net/l2tp/l2tp_core.c contains four suspect calls to l2tp_session_inc_refcount()
^ permalink raw reply [flat|nested] 2+ messages in thread
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