CVE-2026-68247: drm/i915/bios: range check LFP Data Block panel_type2

From: Greg Kroah-Hartman <[email protected]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

drm/i915/bios: range check LFP Data Block panel_type2

While the panel_type from LFP Data Block is range checked, panel_type2
is not. Add a few helpers for range checking, and use them to not only
check panel_type2, but also improve clarity and correctness in the panel
type selection.

Discovered using AI-assisted static analysis confirmed by Intel Product
Security.

v2:
- Fix commit message typo (Michał)
- Add is_panel_type_pnp() (Ville)

(cherry picked from commit c9ebe5d2f25729d6cfbbb1235d640bf67f9275df)

The Linux kernel CVE team has assigned CVE-2026-68247 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.0 with commit 6434cf630086eea2d091f122f5802582a05d9d1c and fixed in 6.12.101 with commit e7b5694645b03e80830dc141b59fc65aac693c70
	Issue introduced in 6.0 with commit 6434cf630086eea2d091f122f5802582a05d9d1c and fixed in 6.18.42 with commit 8b2da44446f9dce2ae50fee78bac2734d4277143
	Issue introduced in 6.0 with commit 6434cf630086eea2d091f122f5802582a05d9d1c and fixed in 7.1.6 with commit 8887b94d2fc93071bf6ff09c39d474510e6f582f
	Issue introduced in 6.0 with commit 6434cf630086eea2d091f122f5802582a05d9d1c and fixed in 7.2-rc2 with commit 2084503f2d087bf956198e7f6eb25b03a7049cb2

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-68247
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/gpu/drm/i915/display/intel_bios.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/e7b5694645b03e80830dc141b59fc65aac693c70
	https://git.kernel.org/stable/c/8b2da44446f9dce2ae50fee78bac2734d4277143
	https://git.kernel.org/stable/c/8887b94d2fc93071bf6ff09c39d474510e6f582f
	https://git.kernel.org/stable/c/2084503f2d087bf956198e7f6eb25b03a7049cb2