linux-cve-announce - CVE-2022-49932: KVM: VMX: Do _all_ initialization before exposing /dev/kvm to userspace

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Message-ID: <2025050257-CVE-2022-49932-17ac@gregkh>
Date: Fri,  2 May 2025 17:54:58 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2022-49932: KVM: VMX: Do _all_ initialization before exposing /dev/kvm to userspace

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

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

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

KVM: VMX: Do _all_ initialization before exposing /dev/kvm to userspace

Call kvm_init() only after _all_ setup is complete, as kvm_init() exposes
/dev/kvm to userspace and thus allows userspace to create VMs (and call
other ioctls).  E.g. KVM will encounter a NULL pointer when attempting to
add a vCPU to the per-CPU loaded_vmcss_on_cpu list if userspace is able to
create a VM before vmx_init() configures said list.

 BUG: kernel NULL pointer dereference, address: 0000000000000008
 #PF: supervisor write access in kernel mode
 #PF: error_code(0x0002) - not-present page
 PGD 0 P4D 0
 Oops: 0002 [#1] SMP
 CPU: 6 PID: 1143 Comm: stable Not tainted 6.0.0-rc7+ #988
 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
 RIP: 0010:vmx_vcpu_load_vmcs+0x68/0x230 [kvm_intel]
  <TASK>
  vmx_vcpu_load+0x16/0x60 [kvm_intel]
  kvm_arch_vcpu_load+0x32/0x1f0 [kvm]
  vcpu_load+0x2f/0x40 [kvm]
  kvm_arch_vcpu_create+0x231/0x310 [kvm]
  kvm_vm_ioctl+0x79f/0xe10 [kvm]
  ? handle_mm_fault+0xb1/0x220
  __x64_sys_ioctl+0x80/0xb0
  do_syscall_64+0x2b/0x50
  entry_SYSCALL_64_after_hwframe+0x46/0xb0
 RIP: 0033:0x7f5a6b05743b
  </TASK>
 Modules linked in: vhost_net vhost vhost_iotlb tap kvm_intel(+) kvm irqbypass

The Linux kernel CVE team has assigned CVE-2022-49932 to this issue.

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

	Fixed in 6.1.20 with commit e136e969d268b9b89329c816c002e53f60e82985
	Fixed in 6.2.7 with commit e28533c08023c4b319b7f2cd77f3f7c9204eb517
	Fixed in 6.3 with commit e32b120071ea114efc0b4ddd439547750b85f618

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-2022-49932
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/kvm/vmx/vmx.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/e136e969d268b9b89329c816c002e53f60e82985
	https://git.kernel.org/stable/c/e28533c08023c4b319b7f2cd77f3f7c9204eb517
	https://git.kernel.org/stable/c/e32b120071ea114efc0b4ddd439547750b85f618