On Tue, Apr 04, 2023 at 09:39:34PM +0200, Daniel Vetter wrote:
> 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.vet...@intel.com>
> Fixes: dc5bdb68b5b3 ("drm/fb-helper: Fix vt restore")
> Cc: Alex Deucher <alexander.deuc...@amd.com>
> Cc: shl...@fastmail.com
> Cc: Michel Dänzer <mic...@daenzer.net>
> Cc: Noralf Trønnes <nor...@tronnes.org>
> Cc: Thomas Zimmermann <tzimmerm...@suse.de>
> Cc: Daniel Vetter <daniel.vet...@intel.com>
> Cc: Maarten Lankhorst <maarten.lankho...@linux.intel.com>
> Cc: Maxime Ripard <mrip...@kernel.org>
> Cc: David Airlie <airl...@linux.ie>
> Cc: Daniel Vetter <dan...@ffwll.ch>
> Cc: dri-de...@lists.freedesktop.org
> Cc: <sta...@vger.kernel.org> # v5.7+
> Cc: Bartlomiej Zolnierkiewicz <b.zolnier...@samsung.com>
> Cc: Geert Uytterhoeven <ge...@linux-m68k.org>
> Cc: Nathan Chancellor <natechancel...@gmail.com>
> Cc: Qiujun Huang <hqjag...@gmail.com>
> Cc: Peter Rosin <p...@axentia.se>
> Cc: linux-fb...@vger.kernel.org
> Cc: Helge Deller <del...@gmx.de>
> Cc: Sam Ravnborg <s...@ravnborg.org>
> Cc: Geert Uytterhoeven <geert+rene...@glider.be>
> Cc: Samuel Thibault <samuel.thiba...@ens-lyon.org>
> Cc: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp>
> Cc: Shigeru Yoshida <syosh...@redhat.com>
An Ack on this (or a better idea) would be great, so I can stuff it into
-fixes.
Thanks, Daniel
> ---
> drivers/video/fbdev/core/fbmem.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> 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;
> console_lock();
> lock_fb_info(info);
> ret = fbcon_modechange_possible(info, &var);
> --
> 2.40.0
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
