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Date: Mon, 18 Apr 2022 14:13:56 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Thomas Osterried <thomas@...erried.de>,
Duoming Zhou <duoming@....edu.cn>,
"David S. Miller" <davem@...emloft.net>,
Ovidiu Panait <ovidiu.panait@...driver.com>
Subject: [PATCH 5.4 59/63] ax25: Fix refcount leaks caused by ax25_cb_del()
From: Duoming Zhou <duoming@....edu.cn>
commit 9fd75b66b8f68498454d685dc4ba13192ae069b0 upstream.
The previous commit d01ffb9eee4a ("ax25: add refcount in ax25_dev to
avoid UAF bugs") and commit feef318c855a ("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: d01ffb9eee4a ("ax25: add refcount in ax25_dev to avoid UAF bugs")
Fixes: 87563a043cef ("ax25: fix reference count leaks of ax25_dev")
Fixes: feef318c855a ("ax25: fix UAF bugs of net_device caused by rebinding operation")
Reported-by: Thomas Osterried <thomas@...erried.de>
Signed-off-by: Duoming Zhou <duoming@....edu.cn>
Signed-off-by: David S. Miller <davem@...emloft.net>
[OP: backport to 5.4: adjust dev_put_track()->dev_put()]
Signed-off-by: Ovidiu Panait <ovidiu.panait@...driver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
net/ax25/af_ax25.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c
@@ -98,8 +98,10 @@ again:
spin_unlock_bh(&ax25_list_lock);
lock_sock(sk);
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);
ax25_disconnect(s, ENETUNREACH);
spin_lock_bh(&ax25_list_lock);
@@ -978,14 +980,20 @@ static int ax25_release(struct socket *s
{
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) {
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