Re: [Xen-devel] Fix PVFB backend to validate frontend's frame buffer description

[Yosuke Iwamatsu <y-iwamatsu@xxxxxxxxxxxxx>]

Hi,

Sorry for late reply.
I found that with this patch applied, qemu-dm got stuck while creating
a domain that had vfb but no 'videoram' parameter in its configuration.
It seems when no 'videoram' is specified, videoram is set to 0 and
xenfb_configure_fb() fails. It results in qemu-dm abort.
Is this an expected behavior? I think we should allow guest domains to
use at least a few MBs of videoram by default.

Thanks,
--Yosuke

Markus Armbruster wrote:
> @@ -745,29 +807,18 @@ static int xenfb_read_frontend_fb_config
>          xenfb_xs_printf(xenfb->xsh, xenfb->fb.nodename, "request-update", "1");
>          xenfb->refresh_period = -1;
>  
> -        /* TODO check for permitted ranges */
> -        fb_page = xenfb->fb.page;
> -        xenfb->depth = fb_page->depth;
> -        xenfb->width = fb_page->width;
> -        xenfb->height = fb_page->height;
> -        /* TODO check for consistency with the above */
> -        xenfb->fb_len = fb_page->mem_length;
> -        xenfb->row_stride = fb_page->line_length;
> -
> -        /* Protect against hostile frontend, limit fb_len to max allowed */
>          if (xenfb_xs_scanf1(xenfb->xsh, xenfb->fb.nodename, "videoram", "%d",
>                              &videoram) < 0)
>                  videoram = 0;
> -        videoram = videoram * 1024 * 1024;
> -        if (videoram && xenfb->fb_len > videoram) {
> -                fprintf(stderr, "Framebuffer requested length of %zd exceeded 
> allowed %d\n",
> -                        xenfb->fb_len, videoram);
> -                xenfb->fb_len = videoram;
> -                if (xenfb->row_stride * xenfb->height > xenfb->fb_len)
> -                        xenfb->height = xenfb->fb_len / xenfb->row_stride;
> -        }
> -        fprintf(stderr, "Framebuffer depth %d width %d height %d line %d\n",
> -                fb_page->depth, fb_page->width, fb_page->height, 
> fb_page->line_length);
> +       fb_page = xenfb->fb.page;
> +       if (xenfb_configure_fb(xenfb, videoram * 1024 * 1024U,
> +                              fb_page->width, fb_page->height, fb_page->depth,
> +                              fb_page->mem_length, 0, fb_page->line_length)
> +           < 0) {
> +               errno = EINVAL;
> +               return -1;
> +       }
> +
>          if (xenfb_map_fb(xenfb, xenfb->fb.otherend_id) < 0)
>                 return -1;
>  
>
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