I noticed a recurring pattern is present in multiple hid devices in the Linux tree, where the LED controller of a device schedules a work_struct to interact with the hardware. The work_struct is embedded in the device structure and thus, is freed at device removal. The issue is that a LED worker may be scheduled by a timer concurrently with device removal, causing the work_struct to be accessed after having been freed. I was able to trigger the issue in hid-bigbenff.c and hid-asus.c where the work_structs may be scheduled by the LED controller while the device is disconnecting, triggering use-after-frees. I can attach the reproducer, but it's very simple USB configuration, using the /dev/raw-gadget interface with some more USB interactions to manage LEDs configuration and pass checks in asus_kbd_init() and asus_kbd_get_functions() in case of hid-asus.c. I triggered the issue by connecting a device and immediately disconnecting it, so that the remove function runs before the LED one which remains pending. More drivers have the same pattern (hid-lg-g15.c, hid-playstation.c, hid-sony.c) but I wasn't able to properly pass the right descriptors to trigger the led configurations needed to trigger the workers. Some other drivers manually unregister at removal (hid-corsair.c, hid-gt683r.c, hid-lenovo.c) since they do not use the managed interface, which is safe, to my understanding. Also, a similar pattern is present with callbacks which schedule a worker originating from input_ff_create_memless() (e.g., in hid-bigbenff.c) but in these cases, I wasn't able to trigger the race condition with the event handling to schedule the worker during device removal. However, I have no experience with the USB protocol and I'm not able to say that they cannot be triggered. I am currently wondering if this is due to some emulation of the /dev/raw-gadget interface or if it's effectively an issue with how each device manages resource removal. But I wonder why syzkaller didn't find any crash while fuzzing the interface with upstream-usb.config, as they seem pretty straightforward to trigger. Configuring the kernel with CONFIG_DEBUG_OBJECTS, it emits a warning in debug_check_no_obj_freed, which makes it clear that device removal is freeing resources in use. KASAN detects them as use-after-free. I am attaching multiple patches for all the drivers I suspect the bug is present. The proposed patches unregister the LED controllers before removing the device itself. I attach the (partial for brevity) ODEBUG dumps: ```hid-bigbenff.c [ 37.803135][ T1170] usb 1-1: USB disconnect, device number 2 [ 37.827979][ T1170] ODEBUG: free active (active state 0) object type: work_struct hint: bigben_worker+0x0/0x860 [ 37.829634][ T1170] WARNING: CPU: 0 PID: 1170 at lib/debugobjects.c:505 debug_check_no_obj_freed+0x43a/0x630 [ 37.830904][ T1170] Modules linked in: [ 37.831413][ T1170] CPU: 0 PID: 1170 Comm: kworker/0:3 Not tainted 6.1.0-rc4-dirty #43 [ 37.832465][ T1170] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 [ 37.833751][ T1170] Workqueue: usb_hub_wq hub_event [ 37.834409][ T1170] RIP: 0010:debug_check_no_obj_freed+0x43a/0x630 [ 37.835218][ T1170] Code: 48 89 ef e8 28 82 58 ff 49 8b 14 24 4c 8b 45 00 48 c7 c7 40 5f 09 87 48 c7 c6 60 5b 09 87 89 d9 4d 89 f9 31 c0 e8 46 25 ef fe <0f> 0b 4c 8b 64 24 20 48 ba 00 00 00 00 00 fc ff df ff 05 4f 7c 17 [ 37.837667][ T1170] RSP: 0018:ffffc900006fee60 EFLAGS: 00010246 [ 37.838503][ T1170] RAX: 0d2d19ffcded3d00 RBX: 0000000000000000 RCX: ffff888117fc9b00 [ 37.839519][ T1170] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 [ 37.840570][ T1170] RBP: ffffffff86e88380 R08: ffffffff8130793b R09: fffff520000dfd85 [ 37.841618][ T1170] R10: fffff520000dfd85 R11: 0000000000000000 R12: ffffffff87095fb8 [ 37.842649][ T1170] R13: ffff888117770ad8 R14: ffff888117770acc R15: ffffffff852b7420 [ 37.843728][ T1170] FS: 0000000000000000(0000) GS:ffff8881f6600000(0000) knlGS:0000000000000000 [ 37.844877][ T1170] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 37.845749][ T1170] CR2: 00007f992eaab380 CR3: 000000011834b000 CR4: 00000000001006f0 [ 37.846794][ T1170] Call Trace: [ 37.847245][ T1170] <TASK> [ 37.847643][ T1170] slab_free_freelist_hook+0x89/0x160 [ 37.848409][ T1170] ? devres_release_all+0x262/0x350 [ 37.849156][ T1170] __kmem_cache_free+0x71/0x110 [ 37.849829][ T1170] devres_release_all+0x262/0x350 [ 37.850478][ T1170] ? devres_release+0x90/0x90 [ 37.851118][ T1170] device_release_driver_internal+0x5e5/0x8a0 [ 37.851944][ T1170] bus_remove_device+0x2ea/0x400 [ 37.852611][ T1170] device_del+0x64f/0xb40 [ 37.853212][ T1170] ? kill_device+0x150/0x150 [ 37.853831][ T1170] ? print_irqtrace_events+0x1f0/0x1f0 [ 37.854564][ T1170] hid_destroy_device+0x66/0x100 [ 37.855226][ T1170] usbhid_disconnect+0x9a/0xc0 [ 37.855887][ T1170] usb_unbind_interface+0x1e1/0x890 ``` ``` hid-asus.c [ 77.409878][ T1169] usb 1-1: USB disconnect, device number 2 [ 77.423606][ T1169] ODEBUG: free active (active state 0) object type: work_struct hint: asus_kbd_backlight_work+0x0/0x2c0 [ 77.425222][ T1169] WARNING: CPU: 0 PID: 1169 at lib/debugobjects.c:505 debug_check_no_obj_freed+0x43a/0x630 [ 77.426599][ T1169] Modules linked in: [ 77.427322][ T1169] CPU: 0 PID: 1169 Comm: kworker/0:3 Not tainted 6.1.0-rc4-dirty #43 [ 77.428404][ T1169] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 [ 77.429644][ T1169] Workqueue: usb_hub_wq hub_event [ 77.430296][ T1169] RIP: 0010:debug_check_no_obj_freed+0x43a/0x630 [ 77.431142][ T1169] Code: 48 89 ef e8 28 82 58 ff 49 8b 14 24 4c 8b 45 00 48 c7 c7 40 5f 09 87 48 c7 c6 60 5b 09 87 89 d9 4d 89 f9 31 c0 e8 46 25 ef fe <0f> 0b 4c 8b 64 24 20 48 ba 00 00 00 00 00 fc ff df ff 05 4f 7c 17 [ 77.433691][ T1169] RSP: 0018:ffffc9000069ee60 EFLAGS: 00010246 [ 77.434470][ T1169] RAX: b85d2b40c12d7600 RBX: 0000000000000000 RCX: ffff888117a78000 [ 77.435507][ T1169] RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000 [ 77.436521][ T1169] RBP: ffffffff86e88380 R08: ffffffff8130793b R09: ffffed103ecc4ed6 [ 77.437582][ T1169] R10: ffffed103ecc4ed6 R11: 0000000000000000 R12: ffffffff87095fb8 [ 77.438593][ T1169] R13: ffff88810e348fe0 R14: ffff88810e348fd4 R15: ffffffff852b5780 [ 77.439667][ T1169] FS: 0000000000000000(0000) GS:ffff8881f6600000(0000) knlGS:0000000000000000 [ 77.440842][ T1169] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 77.441688][ T1169] CR2: 00007ffc05495ff0 CR3: 000000010cdf0000 CR4: 00000000001006f0 [ 77.442720][ T1169] Call Trace: [ 77.443167][ T1169] <TASK> [ 77.443555][ T1169] slab_free_freelist_hook+0x89/0x160 [ 77.444302][ T1169] ? devres_release_all+0x262/0x350 [ 77.444990][ T1169] __kmem_cache_free+0x71/0x110 [ 77.445638][ T1169] devres_release_all+0x262/0x350 [ 77.446309][ T1169] ? devres_release+0x90/0x90 [ 77.446978][ T1169] device_release_driver_internal+0x5e5/0x8a0 [ 77.447748][ T1169] bus_remove_device+0x2ea/0x400 [ 77.448421][ T1169] device_del+0x64f/0xb40 [ 77.448976][ T1169] ? kill_device+0x150/0x150 [ 77.449577][ T1169] ? print_irqtrace_events+0x1f0/0x1f0 [ 77.450307][ T1169] hid_destroy_device+0x66/0x100 [ 77.450938][ T1169] usbhid_disconnect+0x9a/0xc0 ``` To: Jiri Kosina <jikos@xxxxxxxxxx> To: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx> To: Hanno Zulla <kontakt@xxxxxxxx> To: Pavel Machek <pavel@xxxxxx> To: Lee Jones <lee@xxxxxxxxxx> To: Roderick Colenbrander <roderick.colenbrander@xxxxxxxx> To: Sven Eckelmann <sven@xxxxxxxxxxxxx> Cc: linux-leds@xxxxxxxxxxxxxxx Cc: Cristiano Giuffrida <c.giuffrida@xxxxx> Cc: "Bos, H.J." <h.j.bos@xxxxx> Cc: Jakob Koschel <jkl820.git@xxxxxxxxx> Cc: linux-input@xxxxxxxxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx Cc: Jiri Kosina <jkosina@xxxxxxx> Cc: Roderick Colenbrander <roderick@xxxxxxxxxx> Signed-off-by: Pietro Borrello <borrello@xxxxxxxxxxxxxxxx> --- Changes in v2: - dualshock4: Clarify UAF - dualsense: Clarify UAF - dualsense: Unregister multicolor led controller - Link to v1: https://lore.kernel.org/r/20230125-hid-unregister-leds-v1-0-9a5192dcef16@xxxxxxxxxxxxxxxx --- Pietro Borrello (5): HID: bigben_remove: manually unregister leds HID: asus_remove: manually unregister led HID: dualsense_remove: manually unregister leds HID: dualshock4_remove: manually unregister leds HID: sony_remove: manually unregister leds drivers/hid/hid-asus.c | 1 + drivers/hid/hid-bigbenff.c | 5 +++++ drivers/hid/hid-playstation.c | 10 ++++++++++ drivers/hid/hid-sony.c | 8 ++++++++ 4 files changed, 24 insertions(+) --- base-commit: 2241ab53cbb5cdb08a6b2d4688feb13971058f65 change-id: 20230125-hid-unregister-leds-4cbf67099e1d Best regards, -- Pietro Borrello <borrello@xxxxxxxxxxxxxxxx>
