CVE-2026-46245: drm/amd/display: Fix dc_link NULL handling in HPD init

CVE-2026-46245: drm/amd/display: Fix dc_link NULL handling in HPD init

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

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

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

drm/amd/display: Fix dc_link NULL handling in HPD init

amdgpu_dm_hpd_init() may see connectors without a valid dc_link.

The code already checks dc_link for the polling decision, but later
unconditionally dereferences it when setting up HPD interrupts.

Assign dc_link early and skip connectors where it is NULL.

Fixes the below:
drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm_irq.c:940 amdgpu_dm_hpd_init()
error: we previously assumed 'dc_link' could be null (see line 931)

drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm_irq.c
    923                 /*
    924                  * Analog connectors may be hot-plugged unlike other connector
    925                  * types that don't support HPD. Only poll analog connectors.
    926                  */
    927                 use_polling |=
    928                         amdgpu_dm_connector->dc_link &&
                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The patch adds this NULL check but hopefully it can be removed

    929                         dc_connector_supports_analog(amdgpu_dm_connector->dc_link->link_id.id);
    930
    931                 dc_link = amdgpu_dm_connector->dc_link;

dc_link assigned here.

    932
    933                 /*
    934                  * Get a base driver irq reference for hpd ints for the lifetime
    935                  * of dm. Note that only hpd interrupt types are registered with
    936                  * base driver; hpd_rx types aren't. IOW, amdgpu_irq_get/put on
    937                  * hpd_rx isn't available. DM currently controls hpd_rx
    938                  * explicitly with dc_interrupt_set()
    939                  */
--> 940                 if (dc_link->irq_source_hpd != DC_IRQ_SOURCE_INVALID) {
                            ^^^^^^^^^^^^^^^^^^^^^^^ If it's NULL then we are trouble because we dereference it here.

    941                         irq_type = dc_link->irq_source_hpd - DC_IRQ_SOURCE_HPD1;
    942                         /*
    943                          * TODO: There's a mismatch between mode_info.num_hpd
    944                          * and what bios reports as the # of connectors with hpd

The Linux kernel CVE team has assigned CVE-2026-46245 to this issue.


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

	Issue introduced in 4.15 with commit 4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c and fixed in 6.19.4 with commit a490e4d3c9fed1e690c8de348416eea3a9f054ff
	Issue introduced in 4.15 with commit 4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c and fixed in 7.0 with commit 226a40c06a183abaeb7529a4f54d6c203bd14407

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-2026-46245
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/amd/display/amdgpu_dm/amdgpu_dm_irq.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/a490e4d3c9fed1e690c8de348416eea3a9f054ff
	https://git.kernel.org/stable/c/226a40c06a183abaeb7529a4f54d6c203bd14407