CVE-2023-52478

In the Linux kernel, the following vulnerability has been resolved: HID:
logitech-hidpp: Fix kernel crash on receiver USB disconnect
hidpp_connect_event() has four time-of-check vs time-of-use (TOCTOU)
races when it races with itself. hidpp_connect_event() primarily runs from
a workqueue but it also runs on probe() and if a “device-connected” packet
is received by the hw when the thread running hidpp_connect_event() from
probe() is waiting on the hw, then a second thread running
hidpp_connect_event() will be started from the workqueue. This opens the
following races (note the below code is simplified): 1. Retrieving +
printing the protocol (harmless race): if (!hidpp->protocol_major) {
hidpp_root_get_protocol_version() hidpp->protocol_major =
response.rap.params[0]; } We can actually see this race hit in the dmesg in
the abrt output attached to rhbz#2227968: [ 3064.624215]
logitech-hidpp-device 0003:046D:4071.0049: HID++ 4.5 device connected. [
3064.658184] logitech-hidpp-device 0003:046D:4071.0049: HID++ 4.5 device
connected. Testing with extra logging added has shown that after this the 2
threads take turn grabbing the hw access mutex (send_mutex) so they
ping-pong through all the other TOCTOU cases managing to hit all of them:
2. Updating the name to the HIDPP name (harmless race): if (hidpp->name ==
hdev->name) { … hidpp->name = new_name; } 3. Initializing the
power_supply class for the battery (problematic!):
hidpp_initialize_battery() { if (hidpp->battery.ps) return 0;
probe_battery(); /* Blocks, threads take turns executing this */
hidpp->battery.desc.properties = devm_kmemdup(dev, hidpp_battery_props,
cnt, GFP_KERNEL); hidpp->battery.ps =
devm_power_supply_register(&hidpp->hid_dev->dev, &hidpp->battery.desc,
cfg); } 4. Creating delayed input_device (potentially problematic): if
(hidpp->delayed_input) return; hidpp->delayed_input =
hidpp_allocate_input(hdev); The really big problem here is 3. Hitting the
race leads to the following sequence: hidpp->battery.desc.properties =
devm_kmemdup(dev, hidpp_battery_props, cnt, GFP_KERNEL); hidpp->battery.ps
= devm_power_supply_register(&hidpp->hid_dev->dev, &hidpp->battery.desc,
cfg); … hidpp->battery.desc.properties = devm_kmemdup(dev,
hidpp_battery_props, cnt, GFP_KERNEL); hidpp->battery.ps =
devm_power_supply_register(&hidpp->hid_dev->dev, &hidpp->battery.desc,
cfg); So now we have registered 2 power supplies for the same battery,
which looks a bit weird from userspace’s pov but this is not even the
really big problem. Notice how: 1. This is all devm-maganaged 2. The
hidpp->battery.desc struct is shared between the 2 power supplies 3.
hidpp->battery.desc.properties points to the result from the second
devm_kmemdup() This causes a use after free scenario on USB disconnect of
the receiver: 1. The last registered power supply class device gets
unregistered 2. The memory from the last devm_kmemdup() call gets freed,
hidpp->battery.desc.properties now points to freed memory 3. The first
registered power supply class device gets unregistered, this involves
sending a remove uevent to userspace which invokes power_supply_uevent() to
fill the uevent data 4. power_supply_uevent() uses
hidpp->battery.desc.properties which now points to freed memory leading to
backtraces like this one: Sep 22 20:01:35 eric kernel: BUG: unable to
handle page fault for address: ffffb2140e017f08 … Sep 22 20:01:35 eric
kernel: Workqueue: usb_hub_wq hub_event Sep 22 20:01:35 eric kernel: RIP:
0010:power_supply_uevent+0xee/0x1d0 … Sep 22 20:01:35 eric kernel: ?
asm_exc_page_fault+0x26/0x30 Sep 22 20:01:35 eric kernel: ?
power_supply_uevent+0xee/0x1d0 Sep 22 20:01:35 eric kernel: ?
power_supply_uevent+0x10d/0x1d0 Sep 22 20:01:35 eric kernel:
dev_uevent+0x10f/0x2d0 Sep 22 20:01:35 eric kernel:
kobject_uevent_env+0x291/0x680 Sep 22 20:01:35 eric kernel: —truncated—