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

[Jiri Kosina]

CCing Vicki Pfau here ... could you please give your Ack to this fix?

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
> 

-- 
Jiri Kosina
SUSE Labs