drm: Validate requested virtual size against allocated fb size

commit 62fb376e214d3c1bfdf6fbb77dac162f6da04d7e upstream.

mplayer -vo fbdev tries to create a screen that is twice as tall as the
allocated framebuffer for "doublebuffering". By default, and all in-tree
users, only sufficient memory is allocated and mapped to satisfy the
smallest framebuffer and the virtual size is no larger than the actual.
For these users, we should therefore reject any userspace request to
create a screen that requires a buffer larger than the framebuffer
originally allocated.

References: https://bugs.freedesktop.org/show_bug.cgi?id=38138
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index aada26f63decc7a91d2803079dc9795d053ecdc2..7432e724ecbb9e0dd379ed03ff52b3ab75de9a4d 100644 (file)
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -617,9 +617,13 @@ int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
                return -EINVAL;
 
        /* Need to resize the fb object !!! */
-       if (var->bits_per_pixel > fb->bits_per_pixel || var->xres > fb->width || var->yres > fb->height) {
+       if (var->bits_per_pixel > fb->bits_per_pixel ||
+           var->xres > fb->width || var->yres > fb->height ||
+           var->xres_virtual > fb->width || var->yres_virtual > fb->height) {
                DRM_DEBUG("fb userspace requested width/height/bpp is greater than current fb "
-                         "object %dx%d-%d > %dx%d-%d\n", var->xres, var->yres, var->bits_per_pixel,
+                         "request %dx%d-%d (virtual %dx%d) > %dx%d-%d\n",
+                         var->xres, var->yres, var->bits_per_pixel,
+                         var->xres_virtual, var->yres_virtual,
                          fb->width, fb->height, fb->bits_per_pixel);
                return -EINVAL;
        }