CVE-2026-74421: drm/rockchip: dw_dp: Switch to drmm_kzalloc()

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

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

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

drm/rockchip: dw_dp: Switch to drmm_kzalloc()

Driver makes use of drmm_encoder_init() to initialize the encoder and
automatically handle the cleanup by registering drm_encoder_cleanup()
with drmm_add_action().

However, the internal structure containing the encoder part gets
allocated with devm_kzalloc(), which happens while component_bind_all()
is being called from Rockchip DRM driver.  The component framework
further ensures it is deallocated as part of releasing all the resources
claimed during bind, which is triggered from component_unbind_all().

When the reference to the DRM device gets eventually dropped via
drm_dev_put() in rockchip_drm_unbind(), drmm_encoder_alloc_release()
attempts to access the now released encoder structure, leading to
use-after-free.

Ensure driver's internal structure is still reachable on encoder cleanup
by switching from a device-managed allocation to a drm-managed one.

The Linux kernel CVE team has assigned CVE-2026-74421 to this issue.


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

	Issue introduced in 6.18 with commit d68ba7bac9555d05e2f5b310c898b2a5c7eff174 and fixed in 6.18.40 with commit 0d60b835bca42f0f790689dd47819ed881a92ccc
	Issue introduced in 6.18 with commit d68ba7bac9555d05e2f5b310c898b2a5c7eff174 and fixed in 7.1.5 with commit 6b0b92d1110eccccbd5ba2949bd2b9fb6ea5fc12
	Issue introduced in 6.18 with commit d68ba7bac9555d05e2f5b310c898b2a5c7eff174 and fixed in 7.2-rc1 with commit ed9da8d23020352ad24c528db09b5acdd78b81fd

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-2026-74421
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/rockchip/dw_dp-rockchip.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/0d60b835bca42f0f790689dd47819ed881a92ccc
	https://git.kernel.org/stable/c/6b0b92d1110eccccbd5ba2949bd2b9fb6ea5fc12
	https://git.kernel.org/stable/c/ed9da8d23020352ad24c528db09b5acdd78b81fd