Re: [PATCH 2/8] usb: typec: altmodes/displayport: validate count before reading Status Update VDO

[Heikki Krogerus <heikki.krogerus@linux.intel.com>]

On Wed, May 13, 2026 at 05:52:49PM +0200, Greg Kroah-Hartman wrote:
> A broken/malicious device can send the incorrect count for a status
> update VDO, which will cause the kernel to read uninitialized stack data
> and send it off elsewhere.
> 
> Fix this up by correctly verifying the count for the update object.
> 
> Assisted-by: gkh_clanker_t1000
> Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> Cc: stable <stable@kernel.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>

> ---
>  drivers/usb/typec/altmodes/displayport.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/usb/typec/altmodes/displayport.c b/drivers/usb/typec/altmodes/displayport.c
> index 35d9c3086990..263a89c5f324 100644
> --- a/drivers/usb/typec/altmodes/displayport.c
> +++ b/drivers/usb/typec/altmodes/displayport.c
> @@ -405,6 +405,8 @@ static int dp_altmode_vdm(struct typec_altmode *alt,
>  				dp->state = DP_STATE_EXIT_PRIME;
>  			break;
>  		case DP_CMD_STATUS_UPDATE:
> +			if (count < 2)
> +				break;
>  			dp->data.status = *vdo;
>  			ret = dp_altmode_status_update(dp);
>  			break;
> -- 
> 2.54.0

-- 
heikki