fbmem: Check virtual screen sizes in fb_set_var()

Verify that the fbdev or drm driver correctly adjusted the virtual
screen sizes. On failure report the failing driver and reject the screen
size change.

Signed-off-by: Helge Deller <deller@gmx.de>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: stable@vger.kernel.org # v5.4+

diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index 7dc6848a96bb9d1a73e6db61b802da744e78c0b1..7ee6eb2fa715179b4548316ac6c680e795094cb0 100644 (file)
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -1017,6 +1017,16 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var)
        if (ret)
                return ret;
 
+       /* verify that virtual resolution >= physical resolution */
+       if (var->xres_virtual < var->xres ||
+           var->yres_virtual < var->yres) {
+               pr_warn("WARNING: fbcon: Driver '%s' missed to adjust virtual screen size (%ux%u vs. %ux%u)\n",
+                       info->fix.id,
+                       var->xres_virtual, var->yres_virtual,
+                       var->xres, var->yres);
+               return -EINVAL;
+       }
+
        if ((var->activate & FB_ACTIVATE_MASK) != FB_ACTIVATE_NOW)
                return 0;