Re: [PATCH] HID: hid-steam: fix uninit-value access in steam_get_serial

[Vicki Pfau]

Hi Pei,

On 8/3/26 5:58 PM, Pei Xiao wrote:
> 
> 
> 在 2026/8/4 04:39, Vicki Pfau 写道:
>> Hi Jiri,
>>
>> On 8/3/26 12:34 PM, Jiri Kosina wrote:
>>> CCing Vicki Pfau here ... could you please give your Ack to this fix?
>>
>> This was already fixed in 9f8ee99f831b2711624ef81d0abba1d183f28b09 in the series I submitted earlier. I didn't realize there was an open bug report for it.
> Hi maintainer and Vicki,
> I took a look at this commit. In fact, my patch was nearly two months
> earlier than this commit. I had originally thought that this one-line
> patch, especially for an error-path case, had been ignored by the
> maintainer.

Yes, sorry, I wasn't marked as maintainer at the time and didn't notice it before I wrote my equivalent patch. Jiri just happened to merge mine first.

Vicki

> 
> thanks！
> Pei.
>>
>>>
>>> Thanks.
>>>
>>> On Wed, 10 Jun 2026, Pei Xiao wrote:
>>>
>>>> The reply buffer in steam_get_serial() is allocated on the stack without
>>>> initialization. In cases where steam_recv_report() returns a short read or
>>>> an error, not all bytes of the buffer are written, leading to subsequent
>>>> access of uninitialized memory when checking reply[0], reply[1], reply[2].
>>>>
>>>> Zero-initialize the reply array to prevent KMSAN uninit-value warnings.
>>>>
>>>> Logs:
>>>> hid-steam 0003:28DE:1102.0007: unknown main item tag 0x0
>>>> hid-steam 0003:28DE:1102.0007: unknown main item tag 0x0
>>>> hid-steam 0003:28DE:1102.0007: :
>>>> USB HID v7f.fd Device [HID 28de:1102] on usb-dummy_hcd.1-1/input0
>>>> =====================================================
>>>> BUG: KMSAN: uninit-value in steam_get_serial drivers/hid/hid-steam.c:457 [inline]
>>>> BUG: KMSAN: uninit-value in steam_register+0xd83/0x10e0 drivers/hid/hid-steam.c:965
>>>>  steam_get_serial drivers/hid/hid-steam.c:457 [inline]
>>>>  steam_register+0xd83/0x10e0 drivers/hid/hid-steam.c:965
>>>>  steam_probe+0x6f1/0x19b0 drivers/hid/hid-steam.c:1273
>>>>  __hid_device_probe drivers/hid/hid-core.c:2822 [inline]
>>>>  hid_device_probe+0x60d/0xb90 drivers/hid/hid-core.c:2859
>>>>  call_driver_probe drivers/base/dd.c:-1 [inline]
>>>>  really_probe+0x4d5/0xe40 drivers/base/dd.c:709
>>>>  ...
>>>>
>>>> Local variable reply.i created at:
>>>>  steam_get_serial drivers/hid/hid-steam.c:448 [inline]
>>>>  steam_register+0x180/0x10e0 drivers/hid/hid-steam.c:965
>>>>  steam_probe+0x6f1/0x19b0 drivers/hid/hid-steam.c:1273
>>>>
>>>> Reported-by: syzbot+75f3f9bff8c510602d36@xxxxxxxxxxxxxxxxxxxxxxxxx
>>>> Closes: https://lore.kernel.org/lkml/6a27d055.39669fcc.33b062.008d.GAE@xxxxxxxxxx/
>>>> Fixes: c164d6abf384 ("HID: add driver for Valve Steam Controller")
>>>> Signed-off-by: Pei Xiao <xiaopei01@xxxxxxxxxx>
>>>
>>>
>>>
>>>> ---
>>>>  drivers/hid/hid-steam.c | 2 +-
>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/hid/hid-steam.c b/drivers/hid/hid-steam.c
>>>> index 197126d6e081..f65ad1a21c01 100644
>>>> --- a/drivers/hid/hid-steam.c
>>>> +++ b/drivers/hid/hid-steam.c
>>>> @@ -445,7 +445,7 @@ static int steam_get_serial(struct steam_device *steam)
>>>>  	 */
>>>>  	int ret = 0;
>>>>  	u8 cmd[] = {ID_GET_STRING_ATTRIBUTE, sizeof(steam->serial_no), ATTRIB_STR_UNIT_SERIAL};
>>>> -	u8 reply[3 + STEAM_SERIAL_LEN + 1];
>>>> +	u8 reply[3 + STEAM_SERIAL_LEN + 1] = { 0 };
>>>>  
>>>>  	mutex_lock(&steam->report_mutex);
>>>>  	ret = steam_send_report(steam, cmd, sizeof(cmd));
>>>> -- 
>>>> 2.25.1
>>>>
>>>
>>
>> Vicki
>