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

Overview

In the Linux kernel, the following vulnerability has been resolved:

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

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.

Affected

• Linux >= f1a9a149abc86903e81dd1b2e720f3f89874384b < c3597923932bb90d4fc2186aef552f6677175e4a
• Linux >= f1a9a149abc86903e81dd1b2e720f3f89874384b < e0c224c93d10ee38854fdf24c815108aedd3dcb3
• Linux >= f1a9a149abc86903e81dd1b2e720f3f89874384b < 403cc9bd6ccb9fbe68d501c3236e5a6dd5504e14
• Linux >= f1a9a149abc86903e81dd1b2e720f3f89874384b < 3d7a7bac4c75f25b2513505a0ac5ba909588ed2b
• Linux >= f1a9a149abc86903e81dd1b2e720f3f89874384b < 9bdf8c7bfd79f1090e61d28f969b32880fd77bb3
• Linux >= f1a9a149abc86903e81dd1b2e720f3f89874384b < 15b60ade825c8ce9ec560048a4ae3747e4572be3
• Linux >= f1a9a149abc86903e81dd1b2e720f3f89874384b < 0bf253e9ac994cb5329bc87b00bb4eeca9136791
• Linux >= f1a9a149abc86903e81dd1b2e720f3f89874384b < 2ef16934e069d5f771e989d6ee5c3ece5042f3cd
• Linux >= f1a9a149abc86903e81dd1b2e720f3f89874384b < 0af3b89705688af01aa06025b84fa7a1e06ba6cc
• Linux 0e55072e7c63a6569cab1447e9025d160abd9dd9
• Linux >= 3.8.7 < 3.9
• Linux 3.9

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.