Re: [PATCH] rfkill: Fix use-after-free in rfkill_resume()

On Wed, 2020-11-11 at 11:23 +0800, Claire Chang wrote:

On Wed, Nov 11, 2020 at 1:35 AM Johannes Berg [off-list ref] wrote:

quoted

On Tue, 2020-11-10 at 16:49 +0800, Claire Chang wrote:

quoted

If a device is getting removed or reprobed during resume, use-after-free
might happen. For example, h5_btrtl_resume()[drivers/bluetooth/hci_h5.c]
schedules a work queue for device reprobing. During the reprobing, if
rfkill_set_block() in rfkill_resume() is called after the corresponding
*_unregister() and kfree() are called, there will be an use-after-free
in hci_rfkill_set_block()[net/bluetooth/hci_core.c].

Not sure I understand. So you're saying

 * something (h5_btrtl_resume) schedules a worker
 * said worker run, when it runs, calls rfkill_unregister()
 * somehow rfkill_resume() still gets called after this

But that can't really be right, device_del() removes it from the PM
lists?

If device_del() is called right before the device_lock() in device_resume()[1],
it's possible the rfkill device is unregistered, but rfkill_resume is
still called.

OK, I see, thanks for the clarification!

I'll try to add that to the commit message.

Thanks,
johannes