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authorDuoming Zhou <duoming@zju.edu.cn>2022-03-28 21:00:15 +0800
committerPaolo Abeni <pabeni@redhat.com>2022-03-29 10:24:34 +0200
commit82e31755e55fbcea6a9dfaae5fe4860ade17cbc0 (patch)
treea82e3ec65814a3f8816376acf66bc5e7cb746c9c /net
parent5352a761308397a0e6250fdc629bb3f615b94747 (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.c5
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);
}