| Message ID | 20201110084908.219088-1-tientzu@chromium.org |
|---|---|
| State | New |
| Headers | show |
| Series | rfkill: Fix use-after-free in rfkill_resume() | expand |
On Wed, Nov 11, 2020 at 1:35 AM Johannes Berg <johannes@sipsolutions.net> wrote: > > On Tue, 2020-11-10 at 16:49 +0800, Claire Chang wrote: > > 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. We actually hit this during the suspend/resume stress test, although it's rare. I also have a patch with multiple msleep that can 100% reproduce this use-after-free. Happy to share here if needed. [1] https://elixir.bootlin.com/linux/v5.10-rc3/source/drivers/base/power/main.c#L919 Thanks, Claire > > > johannes > >
diff --git a/net/rfkill/core.c b/net/rfkill/core.c index 971c73c7d34c..97101c55763d 100644 --- a/net/rfkill/core.c +++ b/net/rfkill/core.c @@ -876,6 +876,9 @@ static int rfkill_resume(struct device *dev) rfkill->suspended = false; + if (!rfkill->registered) + return 0; + if (!rfkill->persistent) { cur = !!(rfkill->state & RFKILL_BLOCK_SW); rfkill_set_block(rfkill, cur);
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]. BUG: KASAN: use-after-free in hci_rfkill_set_block+0x58/0xc0 [bluetooth] ... Call trace: dump_backtrace+0x0/0x154 show_stack+0x20/0x2c dump_stack+0xbc/0x12c print_address_description+0x88/0x4b0 __kasan_report+0x144/0x168 kasan_report+0x10/0x18 check_memory_region+0x19c/0x1ac __kasan_check_write+0x18/0x24 hci_rfkill_set_block+0x58/0xc0 [bluetooth] rfkill_set_block+0x9c/0x120 rfkill_resume+0x34/0x70 dpm_run_callback+0xf0/0x1f4 device_resume+0x210/0x22c Fix this by checking rfkill->registered in rfkill_resume(). Since device_del() in rfkill_unregister() requires device_lock() and the whole rfkill_resume() is also protected by the same lock in device_resume()[drivers/base/power/main.c], we can make sure either the rfkill->registered is false before rfkill_resume() starts or the rfkill device won't be unregistered before rfkill_resume() returns. Fixes: 8589086f4efd ("Bluetooth: hci_h5: Turn off RTL8723BS on suspend, reprobe on resume") Signed-off-by: Claire Chang <tientzu@chromium.org> --- net/rfkill/core.c | 3 +++ 1 file changed, 3 insertions(+)