ax25: Fix refcount leaks caused by ax25_cb_del()

stable inclusion
from stable-v5.10.112
commit b20a5ab0f5fb175750c6bafd4cf12daccf00c738
bugzilla: 186602, https://gitee.com/src-openeuler/kernel/issues/I5783H
CVE: CVE-2022-1204

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b20a5ab0f5fb175750c6bafd4cf12daccf00c738

--------------------------------

commit 9fd75b66 upstream.

The previous commit d01ffb9e ("ax25: add refcount in ax25_dev to
avoid UAF bugs") and commit feef318c ("ax25: fix UAF bugs of
net_device caused by rebinding operation") increase the refcounts of
ax25_dev and net_device in ax25_bind() and decrease the matching refcounts
in ax25_kill_by_device() in order to prevent UAF bugs, but there are
reference count leaks.

The root cause of refcount leaks is shown below:

     (Thread 1)                      |      (Thread 2)
ax25_bind()                          |
 ...                                 |
 ax25_addr_ax25dev()                 |
  ax25_dev_hold()   //(1)            |
  ...                                |
 dev_hold_track()   //(2)            |
 ...                                 | ax25_destroy_socket()
                                     |  ax25_cb_del()
                                     |   ...
                                     |   hlist_del_init() //(3)
                                     |
                                     |
     (Thread 3)                      |
ax25_kill_by_device()                |
 ...                                 |
 ax25_for_each(s, &ax25_list) {      |
  if (s->ax25_dev == ax25_dev) //(4) |
   ...                               |

Firstly, we use ax25_bind() to increase the refcount of ax25_dev in
position (1) and increase the refcount of net_device in position (2).
Then, we use ax25_cb_del() invoked by ax25_destroy_socket() to delete
ax25_cb in hlist in position (3) before calling ax25_kill_by_device().
Finally, the decrements of refcounts in ax25_kill_by_device() will not
be executed, because no s->ax25_dev equals to ax25_dev in position (4).

This patch adds decrements of refcounts in ax25_release() and use
lock_sock() to do synchronization. If refcounts decrease in ax25_release(),
the decrements of refcounts in ax25_kill_by_device() will not be
executed and vice versa.

Fixes: d01ffb9e ("ax25: add refcount in ax25_dev to avoid UAF bugs")
Fixes: 87563a04 ("ax25: fix reference count leaks of ax25_dev")
Fixes: feef318c ("ax25: fix UAF bugs of net_device caused by rebinding operation")
Reported-by: NThomas Osterried <thomas@osterried.de>
Signed-off-by: NDuoming Zhou <duoming@zju.edu.cn>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
[OP: backport to 5.10: adjust dev_put_track()->dev_put()]
Signed-off-by: NOvidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

conflict:
	net/ax25/af_ax25.c
Signed-off-by: NLu Wei <luwei32@huawei.com>
Reviewed-by: NWei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: NXiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

net/ax25/af_ax25.c

@@ -99,8 +99,10 @@ static void ax25_kill_by_device(struct net_device *dev)
 			lock_sock(sk);
 			ax25_disconnect(s, ENETUNREACH);
 			s->ax25_dev = NULL;
-			dev_put(ax25_dev->dev);
-			ax25_dev_put(ax25_dev);
+			if (sk->sk_socket) {
+				dev_put(ax25_dev->dev);
+				ax25_dev_put(ax25_dev);
+			}
 			release_sock(sk);
 			spin_lock_bh(&ax25_list_lock);
 			sock_put(sk);
@@ -978,14 +980,20 @@ static int ax25_release(struct socket *sock)
 {
 	struct sock *sk = sock->sk;
 	ax25_cb *ax25;
+	ax25_dev *ax25_dev;
 
 	if (sk == NULL)
 		return 0;
 
 	sock_hold(sk);
-	sock_orphan(sk);
 	lock_sock(sk);
+	sock_orphan(sk);
 	ax25 = sk_to_ax25(sk);
+	ax25_dev = ax25->ax25_dev;
+	if (ax25_dev) {
+		dev_put(ax25_dev->dev);
+		ax25_dev_put(ax25_dev);
+	}
 
 	if (sk->sk_type == SOCK_SEQPACKET) {
 		switch (ax25->state) {