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| author | Duoming Zhou <duoming@zju.edu.cn> | 2022-03-18 03:54:04 +0300 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2022-03-21 13:56:19 +0300 |
| commit | 9fd75b66b8f68498454d685dc4ba13192ae069b0 (patch) | |
| tree | 9d4296d8c606ac066cc1f6e3356589798a1597f6 /net/ax25 | |
| parent | 0caf6d9922192dd1afa8dc2131abfb4df1443b9f (diff) | |
| download | linux-9fd75b66b8f68498454d685dc4ba13192ae069b0.tar.xz | |
ax25: Fix refcount leaks caused by ax25_cb_del()
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@osterried.de>
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ax25')
| -rw-r--r-- | net/ax25/af_ax25.c | 14 |
1 files changed, 11 insertions, 3 deletions
diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c index 6bd097180772..cf8847cfc664 100644 --- 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_track(ax25_dev->dev, &ax25_dev->dev_tracker); - ax25_dev_put(ax25_dev); + if (sk->sk_socket) { + 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) { |