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

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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: f1a9a149ab ("HID: magicmouse: fix race between input_register() and probe()")
Link: https://lore.kernel.org/linux-input/20260728185542.65F091F000E9@smtp.kernel.org/
Cc: stable@vger.kernel.org
Signed-off-by: Jose Villaseñor Montfort <pepemontfort@gmail.com>
Reviewed-by: Alec Hall <signshop.alec@gmail.com>
Tested-by: Alec Hall <signshop.alec@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>
This commit is contained in:
Jose Villaseñor Montfort 2026-07-28 22:15:57 -06:00 committed by Jiri Kosina
parent 27b376b945
commit 0af3b89705
1 changed files with 10 additions and 0 deletions
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10
drivers/hid/hid-magicmouse.c
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@ -915,6 +915,16 @@ static int magicmouse_probe(struct hid_device *hdev,
return ret;
}
/*
* When hidinput_connect() fails it frees every input device it
* created, but that does not fail hid_hw_start(): the core simply
* does not claim an input. msc->input, cached in ->input_mapping
* while the report descriptor was parsed, would then be a dangling
* pointer that passes every NULL check. Trust the core's claim.
*/
if (!(hdev->claimed & HID_CLAIMED_INPUT))
msc->input = NULL;
if (is_usb_magicmouse2(id->vendor, id->product) ||
is_usb_magictrackpad2(id->vendor, id->product)) {
timer_setup(&msc->battery_timer, magicmouse_battery_timer_tick, 0);