CVE-2026-68272: drm/amdgpu: validate CP_GFX_SHADOW chunk size in CS pass1

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

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

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

drm/amdgpu: validate CP_GFX_SHADOW chunk size in CS pass1

Add a minimum-length check for the AMDGPU_CHUNK_ID_CP_GFX_SHADOW chunk in
amdgpu_cs_pass1(), matching the gate already present for the IB, FENCE and
BO_HANDLES chunk types.

The CP_GFX_SHADOW case previously shared a bare break with the dependency
and syncobj chunk types, which do not dereference a fixed-size struct. When
userspace submits this chunk with length_dw == 0, vmemdup_array_user() is
called with size 0 and returns ZERO_SIZE_PTR, which passes the IS_ERR()
check. amdgpu_cs_p2_shadow() then dereferences chunk->kdata as a struct
drm_amdgpu_cs_chunk_cp_gfx_shadow (reading shadow->flags), faulting on the
ZERO_SIZE_PTR and causing a NULL-pointer dereference.

This is reachable by an unprivileged process in the render group. Reject
undersized chunks with -EINVAL during pass1 so the bad submission is
rejected before pass2 ever dereferences the data.

(cherry picked from commit 7f61b2eef7415eccdb40850aca0de94211948657)

The Linux kernel CVE team has assigned CVE-2026-68272 to this issue.


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

	Issue introduced in 6.5 with commit ac9287055ff16a092416c76a19006764e4c6a978 and fixed in 6.6.148 with commit 3f190956404da55560056ce20606010e18bc059c
	Issue introduced in 6.5 with commit ac9287055ff16a092416c76a19006764e4c6a978 and fixed in 6.12.101 with commit 2aa9ea2bd5146d237c8cc16d8737d878b0298a94
	Issue introduced in 6.5 with commit ac9287055ff16a092416c76a19006764e4c6a978 and fixed in 6.18.42 with commit 315d2e5741a81b0be763e80413a2677e22b7e596
	Issue introduced in 6.5 with commit ac9287055ff16a092416c76a19006764e4c6a978 and fixed in 7.1.6 with commit 24668ca3ec19434d7a9574bf9112f2b0614c3a4e
	Issue introduced in 6.5 with commit ac9287055ff16a092416c76a19006764e4c6a978 and fixed in 7.2-rc1 with commit 84c4c36acd5c4b2558b5069f869a165b2c655c84

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-2026-68272
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/amdgpu/amdgpu_cs.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/3f190956404da55560056ce20606010e18bc059c
	https://git.kernel.org/stable/c/2aa9ea2bd5146d237c8cc16d8737d878b0298a94
	https://git.kernel.org/stable/c/315d2e5741a81b0be763e80413a2677e22b7e596
	https://git.kernel.org/stable/c/24668ca3ec19434d7a9574bf9112f2b0614c3a4e
	https://git.kernel.org/stable/c/84c4c36acd5c4b2558b5069f869a165b2c655c84