| Message ID | 620e2ee0-b9a3-dbda-a25b-a93e0ed03ec5@i-love.sakura.ne.jp |
|---|---|
| State | New |
| Headers | show |
| Series | USB: cdc-wdm: Fix use after free in service_outstanding_interrupt(). | expand |
Am Sonntag, den 20.12.2020, 00:25 +0900 schrieb Tetsuo Handa: > syzbot is reporting UAF at usb_submit_urb() [1], for > service_outstanding_interrupt() is not checking WDM_DISCONNECTING > before calling usb_submit_urb(). Close the race by doing same checks > wdm_read() does upon retry. But wdm_read() does them with proper locking. > Also, while wdm_read() checks WDM_DISCONNECTING with desc->rlock held, > service_interrupt_work() does not hold desc->rlock. Thus, it is possible > that usb_submit_urb() is called from service_outstanding_interrupt() from > service_interrupt_work() after WDM_DISCONNECTING was set and kill_urbs() > from wdm_disconnect() completed. Thus, move kill_urbs() in > wdm_disconnect() to after cancel_work_sync() (which makes sure that > service_interrupt_work() is no longer running) completed. That seems to be the right approach. You must prevent this helper from being called in the first place. Regards Oliver
diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c index 02d0cfd23bb2..508b1c3f8b73 100644 --- a/drivers/usb/class/cdc-wdm.c +++ b/drivers/usb/class/cdc-wdm.c @@ -465,13 +465,23 @@ static int service_outstanding_interrupt(struct wdm_device *desc) if (!desc->resp_count || !--desc->resp_count) goto out; + if (test_bit(WDM_DISCONNECTING, &desc->flags)) { + rv = -ENODEV; + goto out; + } + if (test_bit(WDM_RESETTING, &desc->flags)) { + rv = -EIO; + goto out; + } + set_bit(WDM_RESPONDING, &desc->flags); spin_unlock_irq(&desc->iuspin); rv = usb_submit_urb(desc->response, GFP_KERNEL); spin_lock_irq(&desc->iuspin); if (rv) { - dev_err(&desc->intf->dev, - "usb_submit_urb failed with result %d\n", rv); + if (!test_bit(WDM_DISCONNECTING, &desc->flags)) + dev_err(&desc->intf->dev, + "usb_submit_urb failed with result %d\n", rv); /* make sure the next notification trigger a submit */ clear_bit(WDM_RESPONDING, &desc->flags); @@ -1027,9 +1037,9 @@ static void wdm_disconnect(struct usb_interface *intf) wake_up_all(&desc->wait); mutex_lock(&desc->rlock); mutex_lock(&desc->wlock); - kill_urbs(desc); cancel_work_sync(&desc->rxwork); cancel_work_sync(&desc->service_outs_intr); + kill_urbs(desc); mutex_unlock(&desc->wlock); mutex_unlock(&desc->rlock);
syzbot is reporting UAF at usb_submit_urb() [1], for service_outstanding_interrupt() is not checking WDM_DISCONNECTING before calling usb_submit_urb(). Close the race by doing same checks wdm_read() does upon retry. Also, while wdm_read() checks WDM_DISCONNECTING with desc->rlock held, service_interrupt_work() does not hold desc->rlock. Thus, it is possible that usb_submit_urb() is called from service_outstanding_interrupt() from service_interrupt_work() after WDM_DISCONNECTING was set and kill_urbs() from wdm_disconnect() completed. Thus, move kill_urbs() in wdm_disconnect() to after cancel_work_sync() (which makes sure that service_interrupt_work() is no longer running) completed. Although it seems to be safe to dereference desc->intf->dev in service_outstanding_interrupt() even if WDM_DISCONNECTING was already set because desc->rlock or cancel_work_sync() prevents wdm_disconnect() from reaching list_del() before service_outstanding_interrupt() completes, let's not emit error message if WDM_DISCONNECTING is set by wdm_disconnect() while usb_submit_urb() is in progress. [1] https://syzkaller.appspot.com/bug?extid=9e04e2df4a32fb661daf Reported-by: syzbot <syzbot+9e04e2df4a32fb661daf@syzkaller.appspotmail.com> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> --- drivers/usb/class/cdc-wdm.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-)