cve/published/2024/CVE-2024-53196.mbox

From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: <linux-cve-announce@vger.kernel.org>
Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org>
Subject: CVE-2024-53196: KVM: arm64: Don't retire aborted MMIO instruction

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

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

KVM: arm64: Don't retire aborted MMIO instruction

Returning an abort to the guest for an unsupported MMIO access is a
documented feature of the KVM UAPI. Nevertheless, it's clear that this
plumbing has seen limited testing, since userspace can trivially cause a
WARN in the MMIO return:

  WARNING: CPU: 0 PID: 30558 at arch/arm64/include/asm/kvm_emulate.h:536 kvm_handle_mmio_return+0x46c/0x5c4 arch/arm64/include/asm/kvm_emulate.h:536
  Call trace:
   kvm_handle_mmio_return+0x46c/0x5c4 arch/arm64/include/asm/kvm_emulate.h:536
   kvm_arch_vcpu_ioctl_run+0x98/0x15b4 arch/arm64/kvm/arm.c:1133
   kvm_vcpu_ioctl+0x75c/0xa78 virt/kvm/kvm_main.c:4487
   __do_sys_ioctl fs/ioctl.c:51 [inline]
   __se_sys_ioctl fs/ioctl.c:893 [inline]
   __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:893
   __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
   invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
   el0_svc_common+0x1e0/0x23c arch/arm64/kernel/syscall.c:132
   do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
   el0_svc+0x38/0x68 arch/arm64/kernel/entry-common.c:712
   el0t_64_sync_handler+0x90/0xfc arch/arm64/kernel/entry-common.c:730
   el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598

The splat is complaining that KVM is advancing PC while an exception is
pending, i.e. that KVM is retiring the MMIO instruction despite a
pending synchronous external abort. Womp womp.

Fix the glaring UAPI bug by skipping over all the MMIO emulation in
case there is a pending synchronous exception. Note that while userspace
is capable of pending an asynchronous exception (SError, IRQ, or FIQ),
it is still safe to retire the MMIO instruction in this case as (1) they
are by definition asynchronous, and (2) KVM relies on hardware support
for pending/delivering these exceptions instead of the software state
machine for advancing PC.

The Linux kernel CVE team has assigned CVE-2024-53196 to this issue.


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

	Issue introduced in 5.5 with commit da345174ceca052469e4775e4ae263b5f27a9355 and fixed in 6.1.120 with commit 6af853cf5f897d55f42e9166f4db50e84e404fb3
	Issue introduced in 5.5 with commit da345174ceca052469e4775e4ae263b5f27a9355 and fixed in 6.6.66 with commit ea6b5d98fea4ee8cb443ea98fda520909e90d30e
	Issue introduced in 5.5 with commit da345174ceca052469e4775e4ae263b5f27a9355 and fixed in 6.11.11 with commit 1e46460efe1ef9a31748de7675ff8fe0d8601af2
	Issue introduced in 5.5 with commit da345174ceca052469e4775e4ae263b5f27a9355 and fixed in 6.12.2 with commit d0571c3add987bcb69c2ffd7a70c998bf8ce60fb
	Issue introduced in 5.5 with commit da345174ceca052469e4775e4ae263b5f27a9355 and fixed in 6.13 with commit e735a5da64420a86be370b216c269b5dd8e830e2

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-2024-53196
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/arm64/kvm/mmio.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/6af853cf5f897d55f42e9166f4db50e84e404fb3
	https://git.kernel.org/stable/c/ea6b5d98fea4ee8cb443ea98fda520909e90d30e
	https://git.kernel.org/stable/c/1e46460efe1ef9a31748de7675ff8fe0d8601af2
	https://git.kernel.org/stable/c/d0571c3add987bcb69c2ffd7a70c998bf8ce60fb
	https://git.kernel.org/stable/c/e735a5da64420a86be370b216c269b5dd8e830e2