Subject: CVE-2021-46907: KVM: VMX: Don't use vcpu->run->internal.ndata as an array index

From: [email-masked]

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

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

KVM: VMX: Don't use vcpu->run->internal.ndata as an array index

__vmx_handle_exit() uses vcpu->run->internal.ndata as an index for
an array access.  Since vcpu->run is (can be) mapped to a user address
space with a writer permission, the 'ndata' could be updated by the
user process at anytime (the user process can set it to outside the
bounds of the array).
So, it is not safe that __vmx_handle_exit() uses the 'ndata' that way.

The Linux kernel CVE team has assigned CVE-2021-46907 to this issue.

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

	Issue introduced in 5.9 with commit 1aa561b1a4c0 and fixed in 5.10.32 with commit 7f64753835a7
	Issue introduced in 5.9 with commit 1aa561b1a4c0 and fixed in 5.11.16 with commit ce541d7b5956
	Issue introduced in 5.9 with commit 1aa561b1a4c0 and fixed in 5.12 with commit 04c4f2ee3f68

Please see https://www.kernel.org or 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-2021-46907
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/7f64753835a78c7d2cc2932a5808ef3b7fd4c050
	https://git.kernel.org/stable/c/ce541d7b59566a0d94c7c99bfb5d34b050e6af70
	https://git.kernel.org/stable/c/04c4f2ee3f68c9a4bf1653d15f1a9a435ae33f7a