[PATCH] net: netrom: Fix potential nr_neigh refcnt leak in nr_add_node

[PATCH] net: netrom: Fix potential nr_neigh refcnt leak in nr_add_node

[Xiyu Yang]

nr_add_node() invokes nr_neigh_get_dev(), which returns a local
reference of the nr_neigh object to "nr_neigh" with increased refcnt.

When nr_add_node() returns, "nr_neigh" becomes invalid, so the refcount
should be decreased to keep refcount balanced.

The issue happens in one normal path of nr_add_node(), which forgets to
decrease the refcnt increased by nr_neigh_get_dev() and causes a refcnt
leak. It should decrease the refcnt before the function returns like
other normal paths do.

Fix this issue by calling nr_neigh_put() before the nr_add_node()
returns.

Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
---
 net/netrom/nr_route.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/netrom/nr_route.c b/net/netrom/nr_route.c
index d41335bad1f8..89cd9de21594 100644
--- a/net/netrom/nr_route.c
+++ b/net/netrom/nr_route.c
@@ -208,6 +208,7 @@ static int __must_check nr_add_node(ax25_address *nr, const char *mnemonic,
 		/* refcount initialized at 1 */
 		spin_unlock_bh(&nr_node_list_lock);
 
+		nr_neigh_put(nr_neigh);
 		return 0;
 	}
 	nr_node_lock(nr_node);
-- 
2.7.4

Re: [PATCH] net: netrom: Fix potential nr_neigh refcnt leak in nr_add_node

[David Miller]

From: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Date: Wed, 15 Apr 2020 16:36:19 +0800

> nr_add_node() invokes nr_neigh_get_dev(), which returns a local
> reference of the nr_neigh object to "nr_neigh" with increased refcnt.
> 
> When nr_add_node() returns, "nr_neigh" becomes invalid, so the refcount
> should be decreased to keep refcount balanced.
> 
> The issue happens in one normal path of nr_add_node(), which forgets to
> decrease the refcnt increased by nr_neigh_get_dev() and causes a refcnt
> leak. It should decrease the refcnt before the function returns like
> other normal paths do.
> 
> Fix this issue by calling nr_neigh_put() before the nr_add_node()
> returns.
> 
> Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
> Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>

Applied and queued up for -stable, thanks.