[PATCH v2 3/4] fbmem: Fix input parameter checks for user-provided screen resolution changes

[Daniel Vetter]

On Sat, Jun 25, 2022 at 02:25:01PM +0200, Helge Deller wrote:
> Enhance the checks in the FBIOPUT_VSCREENINFO ioctl handler to verify
> the user-provided new screen size for:
> 
> a) virtual screen size >= physical screen size, and
> 
> b) new screen size is bigger than currently configured console font size.
> 
> Return -EINVAL on invalid input.
> 
> Signed-off-by: Helge Deller <deller at gmx.de>
> Cc: stable at vger.kernel.org # v5.4+

Imo squash this into the previous one please. Doesn't make sense to split
the patch which adds a function from it's callsite.
-Daniel

> ---
>  drivers/video/fbdev/core/fbmem.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
> index afa2863670f3..50fb66b954d6 100644
> --- a/drivers/video/fbdev/core/fbmem.c
> +++ b/drivers/video/fbdev/core/fbmem.c
> @@ -1106,7 +1106,13 @@ 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);
> +		if (var.xres_virtual < var.xres ||
> +		    var.yres_virtual < var.yres)
> +			ret = -EINVAL;
> +		if (!ret)
> +			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