CVE-2026-72358: drm/xe/pt: prevent invalid cursor access for purged BOs

CVE-2026-72358: drm/xe/pt: prevent invalid cursor access for purged BOs

[Greg Kroah-Hartman]

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

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

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

drm/xe/pt: prevent invalid cursor access for purged BOs

During a page table walk for binding, xe_pt_stage_bind() explicitly
skips initializing the xe_res_cursor for purged BOs, treating them
similarly to NULL VMAs by only setting the cursor size.

However, xe_pt_hugepte_possible() and xe_pt_scan_64K() did not check
if the BO was purged before attempting to walk the cursor using
xe_res_dma() and xe_res_next(). Because the cursor was left
uninitialized for purged BOs, this falls through and triggers
warnings like:

  WARNING: drivers/gpu/drm/xe/xe_res_cursor.h:274 at xe_res_next

Fix this by explicitly checking if the BO is purged in both
xe_pt_hugepte_possible() and xe_pt_scan_64K(), returning early just
as we do for NULL VMAs, avoiding the invalid cursor accesses entirely.

As a precaution, also zero-initialize the cursor in xe_pt_stage_bind()
to ensure we don't pass garbage data into the page table walkers
if we ever hit a similar edge case in the future.

(cherry picked from commit 4c7b9c6ece32440e5a435a92076d049450cd2d2e)

The Linux kernel CVE team has assigned CVE-2026-72358 to this issue.


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

	Issue introduced in 7.1 with commit ad9843aac91a1eda12912a4922042ea04cfc29dc and fixed in 7.1.5 with commit 2b6b3f98d0e93856bee38699b783c71cb0e9d67f
	Issue introduced in 7.1 with commit ad9843aac91a1eda12912a4922042ea04cfc29dc and fixed in 7.2-rc2 with commit 8a0fb57675be578c4db19deb4298ed08a70f0f1a

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-2026-72358
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_pt.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/2b6b3f98d0e93856bee38699b783c71cb0e9d67f
	https://git.kernel.org/stable/c/8a0fb57675be578c4db19deb4298ed08a70f0f1a