Re: [PATCH] drm/gud: NUL-terminate TV mode names read from the device

[Ruben Wauters <rubenru09@aol.com>]

[-- Attachment #1: Type: text/plain, Size: 1826 bytes --]

On Sun, 2026-08-16 at 14:22 +0530, Deepanshu Kartikey wrote:
> gud_connector_add_tv_mode() reads a buffer of fixed-size mode names from
> the USB device and passes pointers into it to
> drm_mode_create_tv_properties_legacy(), which calls strlen() on each one.
> Nothing guarantees the device NUL-terminates a name, so strlen() can run
> past the end of a slot and, for the last mode, past the end of the
> allocation.
> 
> Terminate each name at the end of its slot before use.
> 
> Fixes: 40e1a70b4aed ("drm: Add GUD USB Display driver")
> Reported-by: syzbot+916c888ba5f1a54c9526@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=916c888ba5f1a54c9526
> Tested-by: syzbot+916c888ba5f1a54c9526@syzkaller.appspotmail.com
> Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
Acked-by: Ruben Wauters <rubenru09@aol.com>
> ---
>  drivers/gpu/drm/gud/gud_connector.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/gud/gud_connector.c b/drivers/gpu/drm/gud/gud_connector.c
> index ea0cca58b7c8..5c0065c876a7 100644
> --- a/drivers/gpu/drm/gud/gud_connector.c
> +++ b/drivers/gpu/drm/gud/gud_connector.c
> @@ -396,8 +396,13 @@ static int gud_connector_add_tv_mode(struct gud_device *gdrm, struct drm_connect
>  	}
>  
>  	num_modes = ret / GUD_CONNECTOR_TV_MODE_NAME_LEN;
> -	for (i = 0; i < num_modes; i++)
> -		modes[i] = &buf[i * GUD_CONNECTOR_TV_MODE_NAME_LEN];
> +	for (i = 0; i < num_modes; i++) {
> +		char *mode = &buf[i * GUD_CONNECTOR_TV_MODE_NAME_LEN];
> +
> +		/* The device is not trusted to NUL-terminate the name */
> +		mode[GUD_CONNECTOR_TV_MODE_NAME_LEN - 1] = '\0';
> +		modes[i] = mode;
> +	}
>  
>  	ret = drm_mode_create_tv_properties_legacy(connector->dev, num_modes, modes);
>  free:

[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 870 bytes --]