[PATCH] fbdev: tgafb: Fix potential divide by zero

[Wei Chen]

Dear Helge,

Thank you for the kind words. My real name is Wei Chen.

Please apply this patch to fbdev git tree if it is correct.

Best,
Wei

On Thu, 9 Mar 2023 at 06:05, Helge Deller <deller at gmx.de> wrote:
>
> On 3/7/23 14:08, harperchen wrote:
> > fb_set_var would by called when user invokes ioctl with cmd
> > FBIOPUT_VSCREENINFO. User-provided data would finally reach
> > tgafb_check_var. In case var->pixclock is assigned to zero,
> > divide by zero would occur when checking whether reciprocal
> > of var->pixclock is too high.
> >
> > Similar crashes have happened in other fbdev drivers. There
> > is no check and modification on var->pixclock along the call
> > chain to tgafb_check_var. We believe it could also be triggered
> > in driver tgafb from user site.
> >
> > Signed-off-by: harperchen <harperchen1110 at gmail.com>
>
> Could you provide a real name?
> Otherwise applied to fbdev git tree.
>
> Thanks!
> Helge
>
> > ---
> >   drivers/video/fbdev/tgafb.c | 3 +++
> >   1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/video/fbdev/tgafb.c b/drivers/video/fbdev/tgafb.c
> > index 14d37c49633c..b44004880f0d 100644
> > --- a/drivers/video/fbdev/tgafb.c
> > +++ b/drivers/video/fbdev/tgafb.c
> > @@ -173,6 +173,9 @@ tgafb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
> >   {
> >       struct tga_par *par = (struct tga_par *)info->par;
> >
> > +     if (!var->pixclock)
> > +             return -EINVAL;
> > +
> >       if (par->tga_type == TGA_TYPE_8PLANE) {
> >               if (var->bits_per_pixel != 8)
> >                       return -EINVAL;
>