| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <1a2d0220-5862-4cba-8d0f-2eb7556c9620@kernel.org>
Date: Wed, 23 Jul 2025 06:40:52 +0200
From: Jiri Slaby <jirislaby@...nel.org>
To: Qasim Ijaz <qasdev00@...il.com>
Cc: jikos@...nel.org, bentiss@...nel.org, linux-input@...r.kernel.org,
linux-kernel@...r.kernel.org, stable@...r.kernel.org,
Dmitry Savin <envelsavinds@...il.com>
Subject: Re: [PATCH RESEND] HID: multitouch: fix slab out-of-bounds access in
mt_report_fixup()
On 22. 07. 25, 13:19, Qasim Ijaz wrote:
> On Tue, Jul 22, 2025 at 11:16:15AM +0200, Jiri Slaby wrote:
>> On 22. 07. 25, 10:00, Qasim Ijaz wrote:
>>> 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 vulnerability by ensuring the descriptor size is
>>> greater than or equal to 608 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@...r.kernel.org
>>> Signed-off-by: Qasim Ijaz <qasdev00@...il.com>
>>> Reviewed-by: Dmitry Savin <envelsavinds@...il.com>
>>> ---
>>> drivers/hid/hid-multitouch.c | 25 ++++++++++++++++---------
>>> 1 file changed, 16 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
>>> index 7ac8e16e6158..af4abe3ba410 100644
>>> --- a/drivers/hid/hid-multitouch.c
>>> +++ b/drivers/hid/hid-multitouch.c
>>> @@ -1461,18 +1461,25 @@ 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 (rdesc[607] == 0x15) {
>>> - rdesc[607] = 0x25;
>>> - dev_info(
>>> - &hdev->dev,
>>> - "GT7868Q report descriptor fixup is applied.\n");
>>> + if (*size >= 608) {
>>> + if (rdesc[607] == 0x15) {
>>> + rdesc[607] = 0x25;
>>> + dev_info(
>>> + &hdev->dev,
>>> + "GT7868Q report descriptor fixup is applied.\n");
>>> + } else {
>>> + dev_info(
>>> + &hdev->dev,
>>> + "The byte is not expected for fixing the report descriptor. \
>>> + It's possible that the touchpad firmware is not suitable for applying the fix. \
>>> + got: %x\n",
>>
>> This is wrong. You have all the spaces/tabs in the string now. Drop all the
>> backslashes, and open and close the string on every line.
>>
>>> + rdesc[607]);
>>> + }
>>
>> As this is superlong and superindented, perhaps introduce a new function for
>> these devices?
>>
>>> } else {
>>> dev_info(
>>> &hdev->dev,
>>> - "The byte is not expected for fixing the report descriptor. \
>>> -It's possible that the touchpad firmware is not suitable for applying the fix. \
>>> -got: %x\n",
>>
>> This was horrid too, yeah.
>>
>>> - rdesc[607]);
>>> + "GT7868Q fixup: report descriptor only %u bytes, skipping\n",
>>
>> A predicate missing. Eg. "has only", or "is only".
>>
>
> Thanks for the feedback Jiri, I took the advice on board, is something
> like this better?
Definitely.
> static const __u8 *mt_report_fixup(struct hid_device *hdev, __u8 *rdesc,
> unsigned int *size)
> {
> 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(
> &hdev->dev,
> "GT7868Q fixup: report descriptor fixup is applied.\n");
> } else {
> dev_info(&hdev->dev,
> "GT7868Q fixup: offset 607 is %x (expected 0x15), "
> "descriptor may be malformed, skipping\n",
> rdesc[607]);
> }
> }
>
> return rdesc;
> }
>
> the key changes I made are:
>
> - Move size check to the top, this way the indentation level is decent
> - get rid of message backslashes
> - shorten the fixup failure message when rdesc[607] is not 0x15 and make
> it a bit clearer since this message was the longest - just a minor
> cleanup
> - added "is only %u bytes" as you suggested
>
> if this is all good I can send v2.
I would invert the conditions. So the code would look like:
static bool goodix_needs_fixup(hdev)
{
if (hdev->vendor != I2C_VENDOR_ID_GOODIX)
return false;
return hdev->product == I2C_DEVICE_ID_GOODIX_01E8 ||
hdev->product == I2C_DEVICE_ID_GOODIX_01E9;
}
static const __u8 *mt_report_fixup(struct hid_device *hdev, __u8 *rdesc,
unsigned int *size)
{
if (!goodix_needs_fixup(hdev))
return rdesc;
if (*size < 608) {
dev_info(&hdev->dev,
"GT7868Q fixup: report descriptor is only %u bytes,
skipping\n",
*size);
return rdesc;
}
if (rdesc[607] != 0x15) {
dev_info(&hdev->dev,
"GT7868Q fixup: offset 607 is %x (expected 0x15), descriptor may be
malformed, skipping\n",
rdesc[607]);
return rdesc;
}
rdesc[607] = 0x25;
dev_info(&hdev->dev,
"GT7868Q fixup: report descriptor fixup is applied.\n");
return rdesc;
}
thanks,
--
js
suse labs
Powered by blists - more mailing lists