linux-cve-announce - CVE-2022-49886: x86/tdx: Panic on bad configs that #VE on "private" memory access

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Message-ID: <2025050156-CVE-2022-49886-3c97@gregkh>
Date: Thu,  1 May 2025 16:11:16 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2022-49886: x86/tdx: Panic on bad configs that #VE on "private" memory access

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

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

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

x86/tdx: Panic on bad configs that #VE on "private" memory access

All normal kernel memory is "TDX private memory".  This includes
everything from kernel stacks to kernel text.  Handling
exceptions on arbitrary accesses to kernel memory is essentially
impossible because they can happen in horribly nasty places like
kernel entry/exit.  But, TDX hardware can theoretically _deliver_
a virtualization exception (#VE) on any access to private memory.

But, it's not as bad as it sounds.  TDX can be configured to never
deliver these exceptions on private memory with a "TD attribute"
called ATTR_SEPT_VE_DISABLE.  The guest has no way to *set* this
attribute, but it can check it.

Ensure ATTR_SEPT_VE_DISABLE is set in early boot.  panic() if it
is unset.  There is no sane way for Linux to run with this
attribute clear so a panic() is appropriate.

There's small window during boot before the check where kernel
has an early #VE handler. But the handler is only for port I/O
and will also panic() as soon as it sees any other #VE, such as
a one generated by a private memory access.

[ dhansen: Rewrite changelog and rebase on new tdx_parse_tdinfo().
	   Add Kirill's tested-by because I made changes since
	   he wrote this. ]

The Linux kernel CVE team has assigned CVE-2022-49886 to this issue.

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

	Issue introduced in 5.19 with commit 9a22bf6debbf5169f750af53c7f86eb4e3cd6712 and fixed in 6.0.8 with commit 895c168c8f78079f21ad50fead7593ffa352f795
	Issue introduced in 5.19 with commit 9a22bf6debbf5169f750af53c7f86eb4e3cd6712 and fixed in 6.1 with commit 373e715e31bf4e0f129befe87613a278fac228d3

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-2022-49886
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/coco/tdx/tdx.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/895c168c8f78079f21ad50fead7593ffa352f795
	https://git.kernel.org/stable/c/373e715e31bf4e0f129befe87613a278fac228d3