CVE-2023-52478 Information

Mar 01, 2024 cve

Description

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):

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 rhbz2227968:

[ 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:

Updating the name to the HIDPP name (harmless race):

if (hidpp->name == hdev->name) … hidpp->name = new_name;
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);

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:

This is all devm-maganaged
The hidpp->battery.desc struct is shared between the 2 power supplies
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:

The last registered power supply class device gets unregistered
The memory from the last devm_kmemdup() call gets freed hidpp->battery.desc.properties now points to freed memory
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
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—

Reference

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