[PATCH v3 3/4] fbmem: Check screen resolution change against font size

[Daniel Vetter]

On Sun, Jun 26, 2022 at 01:56:18AM +0200, Helge Deller wrote:
> On 6/26/22 01:12, Helge Deller wrote:
> > On 6/26/22 00:37, Daniel Vetter wrote:
> >> On Sun, Jun 26, 2022 at 12:33:53AM +0200, Daniel Vetter wrote:
> >>> On Sun, Jun 26, 2022 at 12:06:29AM +0200, Helge Deller wrote:
> >>>> Enhance the check in the FBIOPUT_VSCREENINFO ioctl handler to verify if the
> >>>> user-provided new screen size is bigger than the current font size.
> >>>>
> >>>> Signed-off-by: Helge Deller <deller at gmx.de>
> >>>> Cc: stable at vger.kernel.org # v5.4+
> >>>
> >>> Please squash with previous patch. You might also want to add a note there
> >>> that on older kernels backporters need to open-code
> >>> fbcon_info_from_console instead, since it only exists since
> >>> 409d6c95f9c6 ("fbcon: Introduce wrapper for console->fb_info lookup")
> >>
> >> Maybe easier would be to include that patch in the backports instead of
> >> open coding.
> >
> > I was afraid that WARN_CONSOLE_UNLOCKED() hadn't been backported.
> > But it seems it's in v4.19+ (from patch 56e6c104e4f15), so that's ok.
> >
> > So, yes, it seems pushing 409d6c95f9c6 backwards is probably best.
> 
> It would be the best solution, but sadly 409d6c95f9c6 can't easily be backported.
> So, probably my other approach (fix up afterwards with extra patch) is
> the way to go.

Ah right there's some conflicts with the restoration/removal of scroll
accel.

> What's your thought on this ?

I guess just open code in a separate backport is simplest.
-Daniel

> 
> Helge
> 
> 
> 
> > Will try that approach now.
> >
> > Helge
> >
> >  I think that's what Greg generally prefers at least, less
> >> divergence between stable kernels.
> >> -Daniel
> >>
> >>>
> >>> With these two nits: Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> >>>
> >>>> ---
> >>>>  drivers/video/fbdev/core/fbmem.c | 4 +++-
> >>>>  1 file changed, 3 insertions(+), 1 deletion(-)
> >>>>
> >>>> diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
> >>>> index afa2863670f3..160389365a36 100644
> >>>> --- a/drivers/video/fbdev/core/fbmem.c
> >>>> +++ b/drivers/video/fbdev/core/fbmem.c
> >>>> @@ -1106,7 +1106,9 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd,
> >>>>  			return -EFAULT;
> >>>>  		console_lock();
> >>>>  		lock_fb_info(info);
> >>>> -		ret = fb_set_var(info, &var);
> >>>> +		ret = fbcon_modechange_possible(info, &var);
> >>>> +		if (!ret)
> >>>> +			ret = fb_set_var(info, &var);
> >>>>  		if (!ret)
> >>>>  			fbcon_update_vcs(info, var.activate & FB_ACTIVATE_ALL);
> >>>>  		unlock_fb_info(info);
> >>>> --
> >>>> 2.35.3
> >>>>
> >>>
> >>> --
> >>> Daniel Vetter
> >>> Software Engineer, Intel Corporation
> >>> http://blog.ffwll.ch
> >>
> >
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch