Add virtual screen size check to drm_fb_helper_check_var() in
order to validate userspace input.
Found by Linux Verification Center (linuxtesting.org) with syzkaller.
Signed-off-by: Andrey Strachuk <strochuk@xxxxxxxxx>
Fixes: 6c11df58fd1a ("fbmem: Check virtual screen sizes in fb_set_var()")
---
drivers/gpu/drm/drm_fb_helper.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 2d4cee6a10ff..d21fe89358af 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -1355,6 +1355,16 @@ int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
(drm_format_info_block_height(fb->format, 0) > 1))
return -EINVAL;
+ /* verify that virtual resolution >= physical resolution */
+ if (var->xres_virtual < var->xres ||
+ var->yres_virtual < var->yres) {
+ drm_dbg_kms(dev, "requested virtual screen size that is "
+ "below the physical size(%ux%u vs. %ux%u)\n",
+ var->xres_virtual, var->yres_virtual,
+ var->xres, var->yres);
+ return -EINVAL;
+ }
+
/*
* Changes struct fb_var_screeninfo are currently not pushed back
* to KMS, hence fail if different settings are requested.
--
2.25.1
