On Tue, Apr 11, 2023 at 04:03:24PM +0200, Javier Martinez Canillas wrote:
Daniel Vetter daniel.vetter@ffwll.ch writes:
This is an oversight from dc5bdb68b5b3 ("drm/fb-helper: Fix vt restore") - I failed to realize that nasty userspace could set this.
It's not pretty to mix up kernel-internal and userspace uapi flags like this, but since the entire fb_var_screeninfo structure is uapi we'd need to either add a new parameter to the ->fb_set_par callback and fb_set_par() function, which has a _lot_ of users. Or some other fairly ugly side-channel int fb_info. Neither is a pretty prospect.
Instead just correct the issue at hand by filtering out this kernel-internal flag in the ioctl handling code.
Signed-off-by: Daniel Vetter daniel.vetter@intel.com Fixes: dc5bdb68b5b3 ("drm/fb-helper: Fix vt restore")
[..]
diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index 875541ff185b..3fd95a79e4c3 100644 --- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c @@ -1116,6 +1116,8 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd, case FBIOPUT_VSCREENINFO: if (copy_from_user(&var, argp, sizeof(var))) return -EFAULT;
/* only for kernel-internal use */var.activate &= ~FB_ACTIVATE_KD_TEXT;I don't have a better idea on how to fix this and as you said the whole struct fb_var_screeninfo is an uAPI anyways...
Reviewed-by: Javier Martinez Canillas javierm@redhat.com
Thanks for taking a look, merged to drm-misc-fixes.
-- Best regards,
Javier Martinez Canillas Core Platforms Red Hat