linux-cve-announce - CVE-2026-23215: x86/vmware: Fix hypercall clobbers

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Message-ID: <2026021800-CVE-2026-23215-3294@gregkh>
Date: Wed, 18 Feb 2026 15:22:06 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2026-23215: x86/vmware: Fix hypercall clobbers

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

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

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

x86/vmware: Fix hypercall clobbers

Fedora QA reported the following panic:

  BUG: unable to handle page fault for address: 0000000040003e54
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS edk2-20251119-3.fc43 11/19/2025
  RIP: 0010:vmware_hypercall4.constprop.0+0x52/0x90
  ..
  Call Trace:
   vmmouse_report_events+0x13e/0x1b0
   psmouse_handle_byte+0x15/0x60
   ps2_interrupt+0x8a/0xd0
   ...

because the QEMU VMware mouse emulation is buggy, and clears the top 32
bits of %rdi that the kernel kept a pointer in.

The QEMU vmmouse driver saves and restores the register state in a
"uint32_t data[6];" and as a result restores the state with the high
bits all cleared.

RDI originally contained the value of a valid kernel stack address
(0xff5eeb3240003e54).  After the vmware hypercall it now contains
0x40003e54, and we get a page fault as a result when it is dereferenced.

The proper fix would be in QEMU, but this works around the issue in the
kernel to keep old setups working, when old kernels had not happened to
keep any state in %rdi over the hypercall.

In theory this same issue exists for all the hypercalls in the vmmouse
driver; in practice it has only been seen with vmware_hypercall3() and
vmware_hypercall4().  For now, just mark RDI/RSI as clobbered for those
two calls.  This should have a minimal effect on code generation overall
as it should be rare for the compiler to want to make RDI/RSI live
across hypercalls.

The Linux kernel CVE team has assigned CVE-2026-23215 to this issue.

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

	Fixed in 6.12.70 with commit 2f467a92df61eb516a4ec36ee16234dd4e5ccf00
	Fixed in 6.18.10 with commit feb603a69f830acb58f78d604f0c29e63cd38f87
	Fixed in 6.19 with commit 2687c848e57820651b9f69d30c4710f4219f7dbf

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-2026-23215
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:
	arch/x86/include/asm/vmware.h

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/2f467a92df61eb516a4ec36ee16234dd4e5ccf00
	https://git.kernel.org/stable/c/feb603a69f830acb58f78d604f0c29e63cd38f87
	https://git.kernel.org/stable/c/2687c848e57820651b9f69d30c4710f4219f7dbf