[PATCH AUTOSEL 5.4 073/175] audit: fix a net reference leak in audit_send_reply()

Sasha Levin
2020-06-09T00:09:38Z

From: Paul Moore <paul@paul-moore.com>

[ Upstream commit a48b284b403a4a073d8beb72d2bb33e54df67fb6 ]

If audit_send_reply() fails when trying to create a new thread to
send the reply it also fails to cleanup properly, leaking a reference
to a net structure. This patch fixes the error path and makes a
handful of other cleanups that came up while fixing the code.

Reported-by: teroincn@gmail.com
Reviewed-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/audit.c | 50 +++++++++++++++++++++++++++++---------------------
1 file changed, 29 insertions(+), 21 deletions(-)

diff --git a/kernel/audit.c b/kernel/audit.c
index fcfbb3476ccd..a4eeece2eecd 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -923,19 +923,30 @@ struct sk_buff *audit_make_reply(int seq, int type, int done,
return NULL;
}

+static void audit_free_reply(struct audit_reply *reply)
+{
+ if (!reply)
+ return;
+
+ if (reply->skb)
+ kfree_skb(reply->skb);
+ if (reply->net)
+ put_net(reply->net);
+ kfree(reply);
+}
+
static int audit_send_reply_thread(void *arg)
{
struct audit_reply *reply = (struct audit_reply *)arg;
- struct sock *sk = audit_get_sk(reply->net);

audit_ctl_lock();
audit_ctl_unlock();

/* Ignore failure. It'll only happen if the sender goes away,
because our timeout is set to infinite. */
- netlink_unicast(sk, reply->skb, reply->portid, 0);
- put_net(reply->net);
- kfree(reply);
+ netlink_unicast(audit_get_sk(reply->net), reply->skb, reply->portid, 0);
+ reply->skb = NULL;
+ audit_free_reply(reply);
return 0;
}

@@ -949,35 +960,32 @@ static int audit_send_reply_thread(void *arg)
* @payload: payload data
* @size: payload size
*
- * Allocates an skb, builds the netlink message, and sends it to the port id.
- * No failure notifications.
+ * Allocates a skb, builds the netlink message, and sends it to the port id.
*/
static void audit_send_reply(struct sk_buff *request_skb, int seq, int type, int done,
int multi, const void *payload, int size)
{
- struct net *net = sock_net(NETLINK_CB(request_skb).sk);
- struct sk_buff *skb;
struct task_struct *tsk;
- struct audit_reply *reply = kmalloc(sizeof(struct audit_reply),
- GFP_KERNEL);
+ struct audit_reply *reply;

+ reply = kzalloc(sizeof(*reply), GFP_KERNEL);
if (!reply)
return;

- skb = audit_make_reply(seq, type, done, multi, payload, size);
- if (!skb)
- goto out;
-
- reply->net = get_net(net);
+ reply->skb = audit_make_reply(seq, type, done, multi, payload, size);
+ if (!reply->skb)
+ goto err;
+ reply->net = get_net(sock_net(NETLINK_CB(request_skb).sk));
reply->portid = NETLINK_CB(request_skb).portid;
- reply->skb = skb;

tsk = kthread_run(audit_send_reply_thread, reply, "audit_send_reply");
- if (!IS_ERR(tsk))
- return;
- kfree_skb(skb);
-out:
- kfree(reply);
+ if (IS_ERR(tsk))
+ goto err;
+
+ return;
+
+err:
+ audit_free_reply(reply);
}

/*
--
2.25.1