CVE-2025-39806

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

HID: multitouch: fix slab out-of-bounds access in mt_report_fixup()

A malicious HID device can trigger a slab out-of-bounds during

mt_report_fixup() by passing in report descriptor smaller than

607 bytes. mt_report_fixup() attempts to patch byte offset 607

of the descriptor with 0x25 by first checking if byte offset

607 is 0x15 however it lacks bounds checks to verify if the

descriptor is big enough before conducting this check. Fix

this bug by ensuring the descriptor size is at least 608

bytes before accessing it.

Below is the KASAN splat after the out of bounds access happens:

[ 13.671954] ==================================================================

[ 13.672667] BUG: KASAN: slab-out-of-bounds in mt_report_fixup+0x103/0x110

[ 13.673297] Read of size 1 at addr ffff888103df39df by task kworker/0:1/10

[ 13.673297]

[ 13.673297] CPU: 0 UID: 0 PID: 10 Comm: kworker/0:1 Not tainted 6.15.0-00005-gec5d573d83f4-dirty #3

[ 13.673297] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/04

[ 13.673297] Call Trace:

[ 13.673297] <TASK>

[ 13.673297] dump_stack_lvl+0x5f/0x80

[ 13.673297] print_report+0xd1/0x660

[ 13.673297] kasan_report+0xe5/0x120

[ 13.673297] __asan_report_load1_noabort+0x18/0x20

[ 13.673297] mt_report_fixup+0x103/0x110

[ 13.673297] hid_open_report+0x1ef/0x810

[ 13.673297] mt_probe+0x422/0x960

[ 13.673297] hid_device_probe+0x2e2/0x6f0

[ 13.673297] really_probe+0x1c6/0x6b0

[ 13.673297] __driver_probe_device+0x24f/0x310

[ 13.673297] driver_probe_device+0x4e/0x220

[ 13.673297] __device_attach_driver+0x169/0x320

[ 13.673297] bus_for_each_drv+0x11d/0x1b0

[ 13.673297] __device_attach+0x1b8/0x3e0

[ 13.673297] device_initial_probe+0x12/0x20

[ 13.673297] bus_probe_device+0x13d/0x180

[ 13.673297] device_add+0xe3a/0x1670

[ 13.673297] hid_add_device+0x31d/0xa40

[...]