linux-cve-announce - CVE-2022-49963: drm/i915/ttm: fix CCS handling

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Message-ID: <2025061814-CVE-2022-49963-1a09@gregkh>
Date: Wed, 18 Jun 2025 13:00:28 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2022-49963: drm/i915/ttm: fix CCS handling

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

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

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

drm/i915/ttm: fix CCS handling

Crucible + recent Mesa seems to sometimes hit:

GEM_BUG_ON(num_ccs_blks > NUM_CCS_BLKS_PER_XFER)

And it looks like we can also trigger this with gem_lmem_swapping, if we
modify the test to use slightly larger object sizes.

Looking closer it looks like we have the following issues in
migrate_copy():

  - We are using plain integer in various places, which we can easily
    overflow with a large object.

  - We pass the entire object size (when the src is lmem) into
    emit_pte() and then try to copy it, which doesn't work, since we
    only have a few fixed sized windows in which to map the pages and
    perform the copy. With an object > 8M we therefore aren't properly
    copying the pages. And then with an object > 64M we trigger the
    GEM_BUG_ON(num_ccs_blks > NUM_CCS_BLKS_PER_XFER).

So it looks like our copy handling for any object > 8M (which is our
CHUNK_SZ) is currently broken on DG2.

Testcase: igt@..._lmem_swapping
(cherry picked from commit 8676145eb2f53a9940ff70910caf0125bd8a4bc2)

The Linux kernel CVE team has assigned CVE-2022-49963 to this issue.


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

	Issue introduced in 5.19 with commit da0595ae91da837929a00470ab40546090e5b9ae and fixed in 5.19.8 with commit 97434cb55bd884bd268626ec41489f79b261b2d4
	Issue introduced in 5.19 with commit da0595ae91da837929a00470ab40546090e5b9ae and fixed in 6.0 with commit 8d905254162965c8e6be697d82c7dbf5d08f574d

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-2022-49963
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/gt/intel_migrate.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/97434cb55bd884bd268626ec41489f79b261b2d4
	https://git.kernel.org/stable/c/8d905254162965c8e6be697d82c7dbf5d08f574d