CVE-2026-68253: drm/i915/hdcp: check streams[] bounds before overflow

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

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

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

drm/i915/hdcp: check streams[] bounds before overflow

The data->streams[] overflow check is done after the buffer overflow has
already happened. Move the overflow check before the write.

Side note, emitting a warning splat with a backtrace might be overkill
here, but prefer not changing the behaviour other than not doing the
overrun.

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

(cherry picked from commit 9284ab3b6e776c315883ac2611283d263c9460fd)

The Linux kernel CVE team has assigned CVE-2026-68253 to this issue.


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

	Issue introduced in 5.12 with commit e03187e12cae57c09b521b6f7dd7c7f9aa2b62e9 and fixed in 6.6.151 with commit 84351f12390349ba010920fc247e1a0b12e41eb3
	Issue introduced in 5.12 with commit e03187e12cae57c09b521b6f7dd7c7f9aa2b62e9 and fixed in 6.12.103 with commit 2106fb490b2c6003e23ad6ff36ce823a2170e138
	Issue introduced in 5.12 with commit e03187e12cae57c09b521b6f7dd7c7f9aa2b62e9 and fixed in 6.18.42 with commit 3d2ef8d389495e7889c6062d8bddc46d2a5fbdef
	Issue introduced in 5.12 with commit e03187e12cae57c09b521b6f7dd7c7f9aa2b62e9 and fixed in 7.1.6 with commit 984085c5b53572e2e03fd5fc4817e86ef1effc6e
	Issue introduced in 5.12 with commit e03187e12cae57c09b521b6f7dd7c7f9aa2b62e9 and fixed in 7.2-rc2 with commit bbb15a6b042d02e5508a02b4847e02d2579ee7bc

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-2026-68253
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_hdcp.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/84351f12390349ba010920fc247e1a0b12e41eb3
	https://git.kernel.org/stable/c/2106fb490b2c6003e23ad6ff36ce823a2170e138
	https://git.kernel.org/stable/c/3d2ef8d389495e7889c6062d8bddc46d2a5fbdef
	https://git.kernel.org/stable/c/984085c5b53572e2e03fd5fc4817e86ef1effc6e
	https://git.kernel.org/stable/c/bbb15a6b042d02e5508a02b4847e02d2579ee7bc