Re: [Qemu-devel] [PATCH for-3.1 2/2] usb-mtp: outlaw slashes in filenames

[Bandan Das <bsd@redhat.com>]

Gerd Hoffmann <kraxel@redhat.com> writes:

> Slash is unix directory separator, so they are not allowed in filenames.
> Note this also stops the classic escape via "../".
>
> Fixes: CVE-2018-16867
> Reported-by: Michael Hanselmann (hansmi.ch)
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  hw/usb/dev-mtp.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/hw/usb/dev-mtp.c b/hw/usb/dev-mtp.c
> index fbe1ace035..87eeac1084 100644
> --- a/hw/usb/dev-mtp.c
> +++ b/hw/usb/dev-mtp.c
> @@ -1718,6 +1718,12 @@ static void usb_mtp_write_metadata(MTPState *s)
>  
>      filename = utf16_to_str(dataset->length, dataset->filename);
>  
> +    if (strchr(filename, '/')) {
> +        usb_mtp_queue_result(s, RES_INVALID_PARAMETER, d->trans,
> +                             0, 0, 0, 0);
> +        return;
> +    }
> +
>      o = usb_mtp_object_lookup_name(p, filename, dataset->length);
>      if (o != NULL) {
>          next_handle = o->handle;

Should we return PARAMETER_NOT_SUPPORTED instead of INVALID_PARAMETER ?
That's a valid response code for SendObjectInfo acc to the spec.

Bandan