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

[Helge Deller]

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.

What's your thought on this ?

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
>>
>