Re: [PATCH] HID: magicmouse: do not keep a stale msc->input if no input is claimed

[Jiri Kosina]

On Tue, 28 Jul 2026, Jose Villaseñor Montfort wrote:

> magicmouse_input_mapping() caches the first hid_input's input_dev in
> msc->input while the report descriptor is parsed, and the rest of the
> driver treats a non-NULL msc->input as proof that an input device was
> registered.
> 
> That does not hold on the hid-input error path. If hidinput_connect()
> fails -- for instance because input_register_device() returns an error --
> it unwinds through hidinput_disconnect(), which frees every input_dev it
> created, including the one cached in msc->input.
> 
> The failure does not abort the probe. hid_connect() only skips the claim:
> 
> 	if ((connect_mask & HID_CONNECT_HIDINPUT) && !hidinput_connect(hdev,
> 				connect_mask & HID_CONNECT_HIDINPUT_FORCE))
> 		hdev->claimed |= HID_CLAIMED_INPUT;
> 
> and the "device has no listeners" bailout below it does not fire for this
> driver, which sets ->raw_event; on the USB Magic Mouse 2 / Magic Trackpad
> 2 paths hidraw and hiddev are claimed as well. hid_hw_start() therefore
> returns 0 and magicmouse_probe() continues with msc->input pointing at
> freed memory. Being non-NULL, it passes the "input not registered" check
> in probe and the NULL checks in ->raw_event and ->event, so the next
> input report dereferences freed memory.
> 
> Clear msc->input when the HID core did not claim an input device, so the
> existing NULL checks cover this case as well.
> 
> Fixes: f1a9a149abc8 ("HID: magicmouse: fix race between input_register() and probe()")
> Link: https://lore.kernel.org/linux-input/20260728185542.65F091F000E9@xxxxxxxxxxxxxxx/
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Jose Villaseñor Montfort <pepemontfort@xxxxxxxxx>

Applied, thanks.

-- 
Jiri Kosina
SUSE Labs