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

[Helge Deller]

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.

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
>