In appletb_kbd_probe an input handler is initialised and then registered with input core through input_register_handler(). When this happens input core will add the input handler (specifically its node) to the global input_handler_list. The input_handler_list is central to the functionality of input core and is traversed in various places in input core. An example of this is when a new input device is plugged in and gets registered with input core.

The input_handler in probe is allocated as device managed memory. If a probe failure occurs after input_register_handler() the input_handler memory is freed, yet it will remain in the input_handler_list. This effectively means the input_handler_list contains a dangling pointer to data belonging to a freed input handler.

This causes an issue when any other input device is plugged in - in my case I had an old PixArt HP USB optical mouse and I decided to plug it in after a failure occurred after input_register_handler(). This lead to the registration of this input device via input_register_device which involves traversing over every handler in the corrupted input_handler_list and calling input_attach_handler(), giving each handler a chance to bind to newly registered device.

The core of this bug is a UAF which causes memory corruption of input_handler_list and to fix it we must ensure the input handler is unregistered from input core, this is done through input_unregister_handler().

[ 63.191597] ================================================================== [ 63.192094] BUG: KASAN: slab-use-after-free in input_attach_handler.isra.0+0x1a9/0x1e0 [ 63.192094] Read of size 8 at addr ffff888105ea7c80 by task kworker/0:2/54 [ 63.192094] [ 63.192094] CPU: 0 UID: 0 PID: 54 Comm: kworker/0:2 Not tainted 6.16.0-rc2-00321-g2aa6621d [ 63.192094] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.164 [ 63.192094] Workqueue: usb_hub_wq hub_event [ 63.192094] Call Trace: [ 63.192094] <TASK> [ 63.192094] dump_stack_lvl+0x53/0x70 [ 63.192094] print_report+0xce/0x670 [ 63.192094] kasan_report+0xce/0x100 [ 63.192094] input_attach_handler.isra.0+0x1a9/0x1e0 [ 63.192094] input_register_device+0x76c/0xd00 [ 63.192094] hidinput_connect+0x686d/0xad60 [ 63.192094] hid_connect+0xf20/0x1b10 [ 63.192094] hid_hw_start+0x83/0x100 [ 63.192094] hid_device_probe+0x2d1/0x680 [ 63.192094] really_probe+0x1c3/0x690 [ 63.192094] __driver_probe_device+0x247/0x300 [ 63.192094] driver_probe_device+0x49/0x210 [ 63.192094] __device_attach_driver+0x160/0x320 [ 63.192094] bus_for_each_drv+0x10f/0x190 [ 63.192094] __device_attach+0x18e/0x370 [ 63.192094] bus_probe_device+0x123/0x170 [ 63.192094] device_add+0xd4d/0x1460 [ 63.192094] hid_add_device+0x30b/0x910 [ 63.192094] usbhid_probe+0x920/0xe00 [ 63.192094] usb_probe_interface+0x363/0x9a0 [ 63.192094] really_probe+0x1c3/0x690 [ 63.192094] __driver_probe_device+0x247/0x300 [ 63.192094] driver_probe_device+0x49/0x210 [ 63.192094] __device_attach_driver+0x160/0x320 [ 63.192094] bus_for_each_drv+0x10f/0x190 [ 63.192094] __device_attach+0x18e/0x370 [ 63.192094] bus_probe_device+0x123/0x170 [ 63.192094] device_add+0xd4d/0x1460 [ 63.192094] usb_set_configuration+0xd14/0x1880 [ 63.192094] usb_generic_driver_probe+0x78/0xb0 [ 63.192094] usb_probe_device+0xaa/0x2e0 [ 63.192094] really_probe+0x1c3/0x690 [ 63.192094] __driver_probe_device+0x247/0x300 [ 63.192094] driver_probe_device+0x49/0x210 [ 63.192094] __device_attach_driver+0x160/0x320 [ 63.192094] bus_for_each_drv+0x10f/0x190 [ 63.192094] __device_attach+0x18e/0x370 [ 63.192094] bus_probe_device+0x123/0x170 [ 63.192094] device_add+0xd4d/0x1460 [ 63.192094] usb_new_device+0x7b4/0x1000 [ 63.192094] hub_event+0x234d/0x3fa0 [ 63.192094] process_one_work+0x5bf/0xfe0 [ 63.192094] worker_thread+0x777/0x13a0 [ 63.192094] </TASK> [ 63.192094] [ 63.192094] Allocated by task 54: [ 63.192094] kasan_save_stack+0x33/0x60 [ 63.192094] kasan_save_track+0x14/0x30 [ 63.192094] __kasan_kmalloc+0x8f/0xa0 [ 63.192094] __kmalloc_node_track_caller_noprof+0x195/0x420 [ 63.192094] devm_kmalloc+0x74/0x1e0 [ 63.192094] appletb_kbd_probe+0x39/0x440 [ 63.192094] hid_device_probe+0x2d1/0x680 [ 63.192094] really_probe+0x1c3/0x690 [ 63.192094] __driver_probe_device+0x247/0x300 [ 63.192094] driver_probe_device+0x49/0x210 [ 63.192094] __device_attach_driver+0x160/0x320 [...] [ 63.192094] [ 63.192094] Freed by task 54: [ 63.192094] kasan_save_stack+0x33/0x60 [ 63.192094] kasan_save_track+0x14/0x30 [ 63.192094] kasan_save_free_info+0x3b/0x60 [ 63.192094] __kasan_slab_free+0x37/0x50 [ 63.192094] kfree+0xcf/0x360 [ 63.192094] devres_release_group+0x1f8/0x3c0 [ 63.192094] hid_device_probe+0x315/0x680 [ 63.192094] really_probe+0x1c3/0x690 [ 63.192094] __driver_probe_device+0x247/0x300 [ 63.192094] driver_probe_device+0x49/0x210 [ 63.192094] __device_attach_driver+0x160/0x320 [...]

Fixes: 7d62ba8deacf ("HID: hid-appletb-kbd: add support for fn toggle between media and function mode") Cc: stable@vger.kernel.org Reviewed-by: Aditya Garg gargaditya08@live.com Signed-off-by: Qasim Ijaz qasdev00@gmail.com --- v2: - Use correct "Fixes" tag - clean up backtrace by removing "?" entries and a few lower level calls

drivers/hid/hid-appletb-kbd.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-appletb-kbd.c b/drivers/hid/hid-appletb-kbd.c index d11c49665147..271d1b27b8dd 100644 --- a/drivers/hid/hid-appletb-kbd.c +++ b/drivers/hid/hid-appletb-kbd.c @@ -430,13 +430,15 @@ static int appletb_kbd_probe(struct hid_device *hdev, const struct hid_device_id ret = appletb_kbd_set_mode(kbd, appletb_tb_def_mode); if (ret) { dev_err_probe(dev, ret, "Failed to set touchbar mode\n"); - goto close_hw; + goto unregister_handler; }

hid_set_drvdata(hdev, kbd);

return 0;

+unregister_handler: + input_unregister_handler(&kbd->inp_handler); close_hw: if (kbd->backlight_dev) { put_device(&kbd->backlight_dev->dev);