@@ -98,8 +98,10 @@ static void ax25_kill_by_device(struct net_device *dev)
spin_unlock_bh(&ax25_list_lock);
lock_sock(sk);
s->ax25_dev = NULL;
- dev_put_track(ax25_dev->dev, &ax25_dev->dev_tracker);
- ax25_dev_put(ax25_dev);
+ if (sk->sk_wq) {
+ dev_put_track(ax25_dev->dev, &ax25_dev->dev_tracker);
+ ax25_dev_put(ax25_dev);
+ }
ax25_disconnect(s, ENETUNREACH);
release_sock(sk);
spin_lock_bh(&ax25_list_lock);
@@ -979,14 +981,20 @@ 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_track(ax25_dev->dev, &ax25_dev->dev_tracker);
+ ax25_dev_put(ax25_dev);
+ }
if (sk->sk_type == SOCK_SEQPACKET) {
switch (ax25->state) {
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: feef318c855a ("ax25: fix UAF bugs of net_device caused by rebinding operation") Reported-by: Thomas Osterried <thomas@osterried.de> Signed-off-by: Duoming Zhou <duoming@zju.edu.cn> --- Changes in V2: - Add decrements of refcounts in ax25_release(). net/ax25/af_ax25.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)