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

commit 0379eb8691b9c4477da0277ae0832036ca4410b4 upstream.

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
[...]

Fixes: c8000deb6836 ("HID: multitouch: Add support for GT7868Q")
Cc: stable@vger.kernel.org
Signed-off-by: Qasim Ijaz <qasdev00@gmail.com>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Jiri Kosina <jkosina@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index a1c54ffe02b49739c23b27d09062e5cb83614fb6..4c22bd2ba170809cc972ee78361cc7979784a7b5 100644 (file)
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -1461,6 +1461,14 @@ static const __u8 *mt_report_fixup(struct hid_device *hdev, __u8 *rdesc,
        if (hdev->vendor == I2C_VENDOR_ID_GOODIX &&
            (hdev->product == I2C_DEVICE_ID_GOODIX_01E8 ||
             hdev->product == I2C_DEVICE_ID_GOODIX_01E9)) {
+               if (*size < 608) {
+                       dev_info(
+                               &hdev->dev,
+                               "GT7868Q fixup: report descriptor is only %u bytes, skipping\n",
+                               *size);
+                       return rdesc;
+               }
+
                if (rdesc[607] == 0x15) {
                        rdesc[607] = 0x25;
                        dev_info(