2020-04-25 13:09:10

by Xiyu Yang

Subject: [PATCH v2] net/x25: Fix x25_neigh refcnt leak when x25 disconnect

x25_connect() invokes x25_get_neigh(), which returns a reference of the
specified x25_neigh object to "x25->neighbour" with increased refcnt.

When x25 connect success and returns, the reference still be hold by
"x25->neighbour", so the refcount should be decreased in
x25_disconnect() to keep refcount balanced.

The reference counting issue happens in x25_disconnect(), which forgets
to decrease the refcnt increased by x25_get_neigh() in x25_connect(),
causing a refcnt leak.

Fix this issue by calling x25_neigh_put() before x25_disconnect()
returns.

Signed-off-by: Xiyu Yang <[email protected]>
Signed-off-by: Xin Tan <[email protected]>
---
Changes in v2:
- Fix x25_neigh refcnt leak in x25_disconnect() rather than in
x25_connect()
---
net/x25/x25_subr.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/net/x25/x25_subr.c b/net/x25/x25_subr.c
index 8aa415a38814..8b1b06cabcbf 100644
--- a/net/x25/x25_subr.c
+++ b/net/x25/x25_subr.c
@@ -357,6 +357,10 @@ void x25_disconnect(struct sock *sk, int reason, unsigned char cause,
sk->sk_state_change(sk);
sock_set_flag(sk, SOCK_DEAD);
}
+ read_lock_bh(&x25_list_lock);
+ x25_neigh_put(x25->neighbour);
+ x25->neighbour = NULL;
+ read_unlock_bh(&x25_list_lock);
}

/*
--
2.7.4

2020-04-27 18:23:01

by David Miller

Subject: Re: [PATCH v2] net/x25: Fix x25_neigh refcnt leak when x25 disconnect

From: Xiyu Yang <[email protected]>
Date: Sat, 25 Apr 2020 21:06:25 +0800

> x25_connect() invokes x25_get_neigh(), which returns a reference of the
> specified x25_neigh object to "x25->neighbour" with increased refcnt.
>
> When x25 connect success and returns, the reference still be hold by
> "x25->neighbour", so the refcount should be decreased in
> x25_disconnect() to keep refcount balanced.
>
> The reference counting issue happens in x25_disconnect(), which forgets
> to decrease the refcnt increased by x25_get_neigh() in x25_connect(),
> causing a refcnt leak.
>
> Fix this issue by calling x25_neigh_put() before x25_disconnect()
> returns.
>
> Signed-off-by: Xiyu Yang <[email protected]>
> Signed-off-by: Xin Tan <[email protected]>

Applied.