Hi Doug,

On Mon, Oct 4, 2021 at 6:26 PM Doug Anderson [off-list ref] wrote:

On Mon, Oct 4, 2021 at 8:42 AM Geert Uytterhoeven [off-list ref] wrote:

quoted

quoted

-       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...

quoted

+                       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:

It doesn't happen all the time.  Looks like my EDID is only invalid after
a reset needed to resolve an s2ram crash in the adv7511 driver...

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

Thanks for the quick fix!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds