Re: [PATCH v5 02/15] drm/edid: Break out reading block 0 of the EDID

[Doug Anderson]

Hi,

On Mon, Oct 4, 2021 at 8:42 AM Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote:
>
> > -       if ((edid = kmalloc(EDID_LENGTH, GFP_KERNEL)) == NULL)
> > +       edid = (u8 *)drm_do_get_edid_base_block(get_edid_block, data,
> > +                                               &connector->edid_corrupt,
> > +                                               &connector->null_edid_counter);
> > +       if (IS_ERR_OR_NULL(edid)) {
> > +               if (IS_ERR(edid))
>
> So edid is an error code, not a valid pointer...
>
> > +                       connector_bad_edid(connector, edid, 1);
>
> ... while connector_bad_edid() expects edid to be a valid pointer,
> causing a crash:
>
> Unable to handle kernel NULL pointer dereference at virtual address

Sigh. Thanks for the report and analysis. I guess I don't have any
displays reporting invalid EDIDs to test with. Hopefully this will
help:

https://lore.kernel.org/r/20211004092100.1.Ic90a5ebd44c75db963112be167a03cc96f9fb249@changeid/

-Doug