[PATCH v2] HID: appletb-kbd: fix memory corruption of input_handler_list

[PATCH v2] HID: appletb-kbd: fix memory corruption of input_handler_list

[Qasim Ijaz]

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);
-- 
2.39.5

Re: [PATCH v2] HID: appletb-kbd: fix memory corruption of input_handler_list

[Jiri Kosina]

On Fri, 27 Jun 2025, Qasim Ijaz wrote:

> 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().

Applied to hid.git#for-6.16/upstream-fixes, thanks!

-- 
Jiri Kosina
SUSE Labs

Re: [PATCH v2] HID: appletb-kbd: fix memory corruption of input_handler_list

[Qasim Ijaz]

On Thu, Jul 03, 2025 at 09:38:27AM +0200, Jiri Kosina wrote:
> On Fri, 27 Jun 2025, Qasim Ijaz wrote:
> 
> > 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().
> 
> Applied to hid.git#for-6.16/upstream-fixes, thanks!

Thanks Jiri, would it also be possible to apply this one too: 
<https://lore.kernel.org/all/20250624125256.20473-1-qasdev00@gmail.com/>

Its a bug fix I sent before this a while back but I think it may have been buried
deep down in your inbox causing you to miss it.

Thanks,
Qasim
> 
> -- 
> Jiri Kosina
> SUSE Labs
>