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

[Vicki Pfau <vi@endrift.com>]

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.

> 
> 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@syzkaller.appspotmail.com
>> Closes: https://lore.kernel.org/lkml/6a27d055.39669fcc.33b062.008d.GAE@google.com/
>> Fixes: c164d6abf384 ("HID: add driver for Valve Steam Controller")
>> Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>
> 
> 
> 
>> ---
>>  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