CVE-2026-80887: drm/vmwgfx: use check_add_overflow for shader size+offset bound

CVE-2026-80887: drm/vmwgfx: use check_add_overflow for shader size+offset bound

[Greg Kroah-Hartman]

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

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

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

drm/vmwgfx: use check_add_overflow for shader size+offset bound

vmw_shader_define() validates the user-supplied shader window against
its backing buffer with

	(u64)buffer->tbo.base.size < (u64)size + (u64)offset

drm_vmw_shader_create_arg::offset is __u64 in the uapi; when it is
near U64_MAX the unsigned addition wraps and the resulting tiny value
passes the check.  The unbounded offset is then stored in
res->guest_memory_offset and forwarded to host SVGA shader-create
commands.

Use check_add_overflow() to detect the wrap and compare the resulting
endpoint against the buffer size.

The Linux kernel CVE team has assigned CVE-2026-80887 to this issue.


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

	Issue introduced in 6.4 with commit 668b206601c5f5063e03b76784a0d3024fa2b249 and fixed in 6.6.151 with commit 1bbe7751f5ebac383405ef29a66622d65bd505d3
	Issue introduced in 6.4 with commit 668b206601c5f5063e03b76784a0d3024fa2b249 and fixed in 6.12.103 with commit d3f44438aa805270aaead3b6840ccaea0f4c11f9
	Issue introduced in 6.4 with commit 668b206601c5f5063e03b76784a0d3024fa2b249 and fixed in 6.18.44 with commit cfd163169af3be56eaef113c680ea251f0d09189
	Issue introduced in 6.4 with commit 668b206601c5f5063e03b76784a0d3024fa2b249 and fixed in 7.1.8 with commit 5c725901908eb1e52a16fc0e2373cb761df42d21
	Issue introduced in 6.4 with commit 668b206601c5f5063e03b76784a0d3024fa2b249 and fixed in 7.2 with commit 54d56d5b42d2e4c72ba6e365e9774da90698aa22

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-2026-80887
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/vmwgfx/vmwgfx_shader.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/1bbe7751f5ebac383405ef29a66622d65bd505d3
	https://git.kernel.org/stable/c/d3f44438aa805270aaead3b6840ccaea0f4c11f9
	https://git.kernel.org/stable/c/cfd163169af3be56eaef113c680ea251f0d09189
	https://git.kernel.org/stable/c/5c725901908eb1e52a16fc0e2373cb761df42d21
	https://git.kernel.org/stable/c/54d56d5b42d2e4c72ba6e365e9774da90698aa22