[PATCH 5.15 160/230] fbmem: Check virtual screen sizes in fb_set_var()

Greg Kroah-Hartman
2022-07-11T09:56:49Z

From: Helge Deller <deller@gmx.de>

commit 6c11df58fd1ac0aefcb3b227f72769272b939e56 upstream.

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+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/video/fbdev/core/fbmem.c | 10 ++++++++++
1 file changed, 10 insertions(+)

--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -1020,6 +1020,16 @@ fb_set_var(struct fb_info *info, struct
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;