CVE-2026-74444: drm/vmwgfx: validate DRAW_PRIMITIVES header size before division

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

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

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

drm/vmwgfx: validate DRAW_PRIMITIVES header size before division

vmw_cmd_draw() computes

	maxnum = (header->size - sizeof(cmd->body)) / sizeof(*decl);

where header->size is u32 and is taken straight from the user-supplied
command stream.  When header->size is less than sizeof(cmd->body) the
unsigned subtraction wraps to nearly 4 GiB, producing a huge maxnum.
Any user-controlled cmd->body.numVertexDecls then passes the bound and
the loop dereferences decl[i] far past the end of the kernel command
bounce buffer, producing an out-of-bounds read of kernel memory.

Reject undersized headers up front.

The Linux kernel CVE team has assigned CVE-2026-74444 to this issue.


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

	Issue introduced in 2.6.33 with commit 7a73ba7469cbea631050094fd14f73acebb97cf9 and fixed in 6.6.151 with commit 2666cddf0dd218aa9bd1f99db688d1b532eac21a
	Issue introduced in 2.6.33 with commit 7a73ba7469cbea631050094fd14f73acebb97cf9 and fixed in 6.12.103 with commit fc0c02f510e41650df3479f96e257acf87d8a20a
	Issue introduced in 2.6.33 with commit 7a73ba7469cbea631050094fd14f73acebb97cf9 and fixed in 6.18.44 with commit dc0be7662b7b0ce28cb5eea864737793ed7b9e70
	Issue introduced in 2.6.33 with commit 7a73ba7469cbea631050094fd14f73acebb97cf9 and fixed in 7.1.8 with commit c77cf8edae2bd3a1599115301cc7c98d0c78e731
	Issue introduced in 2.6.33 with commit 7a73ba7469cbea631050094fd14f73acebb97cf9 and fixed in 7.2-rc6 with commit 85891d174707d8bddcec7a888fb4e1d17def34f3

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-2026-74444
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_execbuf.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/2666cddf0dd218aa9bd1f99db688d1b532eac21a
	https://git.kernel.org/stable/c/fc0c02f510e41650df3479f96e257acf87d8a20a
	https://git.kernel.org/stable/c/dc0be7662b7b0ce28cb5eea864737793ed7b9e70
	https://git.kernel.org/stable/c/c77cf8edae2bd3a1599115301cc7c98d0c78e731
	https://git.kernel.org/stable/c/85891d174707d8bddcec7a888fb4e1d17def34f3