Subject: CVE-2024-38610: drivers/virt/acrn: fix PFNMAP PTE checks in acrn_vm_ram_map()

From: Greg Kroah-Hartman <[email-masked]>

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

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

drivers/virt/acrn: fix PFNMAP PTE checks in acrn_vm_ram_map()

Patch series "mm: follow_pte() improvements and acrn follow_pte() fixes".

Patch #1 fixes a bunch of issues I spotted in the acrn driver.  It
compiles, that's all I know.  I'll appreciate some review and testing from
acrn folks.

Patch #2+#3 improve follow_pte(), passing a VMA instead of the MM, adding
more sanity checks, and improving the documentation.  Gave it a quick test
on x86-64 using VM_PAT that ends up using follow_pte().

This patch (of 3):

We currently miss handling various cases, resulting in a dangerous
follow_pte() (previously follow_pfn()) usage.

(1) We're not checking PTE write permissions.

Maybe we should simply always require pte_write() like we do for
pin_user_pages_fast(FOLL_WRITE)? Hard to tell, so let's check for
ACRN_MEM_ACCESS_WRITE for now.

(2) We're not rejecting refcounted pages.

As we are not using MMU notifiers, messing with refcounted pages is
dangerous and can result in use-after-free. Let's make sure to reject them.

(3) We are only looking at the first PTE of a bigger range.

We only lookup a single PTE, but memmap->len may span a larger area.
Let's loop over all involved PTEs and make sure the PFN range is
actually contiguous. Reject everything else: it couldn't have worked
either way, and rather made use access PFNs we shouldn't be accessing.

The Linux kernel CVE team has assigned CVE-2024-38610 to this issue.

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

	Issue introduced in 5.15.33 with commit b9c43aa0b18d and fixed in 5.15.161 with commit 5c6705aa47b5
	Issue introduced in 5.18 with commit 8a6e85f75a83 and fixed in 6.1.93 with commit afeb0e696276
	Issue introduced in 5.18 with commit 8a6e85f75a83 and fixed in 6.6.33 with commit e873f36ec890
	Issue introduced in 5.18 with commit 8a6e85f75a83 and fixed in 6.8.12 with commit 4c4ba3cf3a15
	Issue introduced in 5.18 with commit 8a6e85f75a83 and fixed in 6.9.3 with commit 2c8d6e24930b
	Issue introduced in 5.18 with commit 8a6e85f75a83 and fixed in 6.10 with commit 3d6586008f7b
	Issue introduced in 5.16.19 with commit 149d5fb7e012
	Issue introduced in 5.17.2 with commit 02098ac42b7f

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-2024-38610
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:
	drivers/virt/acrn/mm.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/5c6705aa47b5b78d7ad36fea832bb69caa5bf49a
	https://git.kernel.org/stable/c/afeb0e69627695f759fc73c39c1640dbf8649b32
	https://git.kernel.org/stable/c/e873f36ec890bece26ecce850e969917bceebbb6
	https://git.kernel.org/stable/c/4c4ba3cf3a15ccfbaf787d0296fa42cdb00da9b4
	https://git.kernel.org/stable/c/2c8d6e24930b8ef7d4a81787627c559ae0e0d3bb
	https://git.kernel.org/stable/c/3d6586008f7b638f91f3332602592caa8b00b559