CVE-2026-72359: drm/xe: fix NPD in bo_meminfo()

CVE-2026-72359: drm/xe: fix NPD in bo_meminfo()

[Greg Kroah-Hartman]

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

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

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

drm/xe: fix NPD in bo_meminfo()

When a buffer object is purged, its ttm.resource is set to NULL via the
TTM pipeline gutting flow. However, the BO remains in the client's
object list until userspace explicitly closes the GEM handle. If memory
stats are queried during this time, accessing bo->ttm.resource->mem_type
will result in a NULL pointer dereference.

Fix this by safely skipping purged BOs in bo_meminfo, as they no longer
consume any memory.

User is getting NPD on device resume, and possible theory is that in
bo_move(), if we need to evict something to SYSTEM to save the CCS state,
but the BO is marked as dontneed, this won't trigger a move but will
nuke the pages, leaving us with a NULL bo resource. And the meminfo()
doesn't look ready to handle a NULL resource.

v2 (Sashiko):
 - There could potentially be other cases where we might end up with a
   NULL resource, so make this a general NULL check for now.

(cherry picked from commit c9a8e7daa0afe3161111e27fd92176e608c7f186)

The Linux kernel CVE team has assigned CVE-2026-72359 to this issue.


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

	Issue introduced in 7.1 with commit ad9843aac91a1eda12912a4922042ea04cfc29dc and fixed in 7.1.5 with commit 5ff2212f0e0779b0b0cbf91fbf970144107c4257
	Issue introduced in 7.1 with commit ad9843aac91a1eda12912a4922042ea04cfc29dc and fixed in 7.2-rc2 with commit b5c55015d4164a0f206bcdcf2985da948b3c7837

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-2026-72359
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/xe/xe_drm_client.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/5ff2212f0e0779b0b0cbf91fbf970144107c4257
	https://git.kernel.org/stable/c/b5c55015d4164a0f206bcdcf2985da948b3c7837