[PATCH net 2/2] ax25: fix potential reference counting leak in ax25_addr_ax25dev

[Duoming Zhou]

The reference counting of ax25_dev potentially increase more
than once in ax25_addr_ax25dev(), which will cause memory leak.

In order to fix the above issue, only increase the reference
counting of ax25_dev once, when the res is not null.

Fixes: d01ffb9eee4a ("ax25: add refcount in ax25_dev to avoid UAF bugs")
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Duoming Zhou <duoming@xxxxxxxxxx>
---
 net/ax25/ax25_dev.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ax25/ax25_dev.c b/net/ax25/ax25_dev.c
index 07723095c60..945af92a7b6 100644
--- a/net/ax25/ax25_dev.c
+++ b/net/ax25/ax25_dev.c
@@ -37,8 +37,9 @@ ax25_dev *ax25_addr_ax25dev(ax25_address *addr)
 	for (ax25_dev = ax25_dev_list; ax25_dev != NULL; ax25_dev = ax25_dev->next)
 		if (ax25cmp(addr, (const ax25_address *)ax25_dev->dev->dev_addr) == 0) {
 			res = ax25_dev;
-			ax25_dev_hold(ax25_dev);
 		}
+	if (res)
+		ax25_dev_hold(ax25_dev);
 	spin_unlock_bh(&ax25_dev_lock);
 
 	return res;
-- 
2.17.1