diff options
| author | Duoming Zhou | 2022-03-28 21:00:15 +0800 |
|---|---|---|
| committer | Paolo Abeni | 2022-03-29 10:24:34 +0200 |
| commit | 82e31755e55fbcea6a9dfaae5fe4860ade17cbc0 (patch) | |
| tree | a82e3ec65814a3f8816376acf66bc5e7cb746c9c /net | |
| parent | 5352a761308397a0e6250fdc629bb3f615b94747 (diff) | |
ax25: Fix UAF bugs in ax25 timers
There are race conditions that may lead to UAF bugs in
ax25_heartbeat_expiry(), ax25_t1timer_expiry(), ax25_t2timer_expiry(),
ax25_t3timer_expiry() and ax25_idletimer_expiry(), when we call
ax25_release() to deallocate ax25_dev.
One of the UAF bugs caused by ax25_release() is shown below:
(Thread 1) | (Thread 2)
ax25_dev_device_up() //(1) |
... | ax25_kill_by_device()
ax25_bind() //(2) |
ax25_connect() | ...
ax25_std_establish_data_link() |
ax25_start_t1timer() | ax25_dev_device_down() //(3)
mod_timer(&ax25->t1timer,..) |
| ax25_release()
(wait a time) | ...
| ax25_dev_put(ax25_dev) //(4)FREE
ax25_t1timer_expiry() |
ax25->ax25_dev->values[..] //USE| ...
... |
We increase the refcount of ax25_dev in position (1) and (2), and
decrease the refcount of ax25_dev in position (3) and (4).
The ax25_dev will be freed in position (4) and be used in
ax25_t1timer_expiry().
The fail log is shown below:
==============================================================
[ 106.116942] BUG: KASAN: use-after-free in ax25_t1timer_expiry+0x1c/0x60
[ 106.116942] Read of size 8 at addr ffff88800bda9028 by task swapper/0/0
[ 106.116942] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.17.0-06123-g0905eec574
[ 106.116942] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-14
[ 106.116942] Call Trace:
...
[ 106.116942] ax25_t1timer_expiry+0x1c/0x60
[ 106.116942] call_timer_fn+0x122/0x3d0
[ 106.116942] __run_timers.part.0+0x3f6/0x520
[ 106.116942] run_timer_softirq+0x4f/0xb0
[ 106.116942] __do_softirq+0x1c2/0x651
...
This patch adds del_timer_sync() in ax25_release(), which could ensure
that all timers stop before we deallocate ax25_dev.
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Diffstat (limited to 'net')
| -rw-r--r-- | net/ax25/af_ax25.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c index f5686c463bc0..363d47f94532 100644 --- a/net/ax25/af_ax25.c +++ b/net/ax25/af_ax25.c @@ -1053,6 +1053,11 @@ static int ax25_release(struct socket *sock) ax25_destroy_socket(ax25); } if (ax25_dev) { + del_timer_sync(&ax25->timer); + del_timer_sync(&ax25->t1timer); + del_timer_sync(&ax25->t2timer); + del_timer_sync(&ax25->t3timer); + del_timer_sync(&ax25->idletimer); dev_put_track(ax25_dev->dev, &ax25_dev->dev_tracker); ax25_dev_put(ax25_dev); } |