Subject: CVE-2023-52455: iommu: Don't reserve 0-length IOVA region

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

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

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

iommu: Don't reserve 0-length IOVA region

When the bootloader/firmware doesn't setup the framebuffers, their
address and size are 0 in "iommu-addresses" property. If IOVA region is
reserved with 0 length, then it ends up corrupting the IOVA rbtree with
an entry which has pfn_hi < pfn_lo.
If we intend to use display driver in kernel without framebuffer then
it's causing the display IOMMU mappings to fail as entire valid IOVA
space is reserved when address and length are passed as 0.
An ideal solution would be firmware removing the "iommu-addresses"
property and corresponding "memory-region" if display is not present.
But the kernel should be able to handle this by checking for size of
IOVA region and skipping the IOVA reservation if size is 0. Also, add
a warning if firmware is requesting 0-length IOVA region reservation.

The Linux kernel CVE team has assigned CVE-2023-52455 to this issue.

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

	Issue introduced in 6.3 with commit a5bf3cfce8cb and fixed in 6.6.14 with commit 98b8a550da83
	Issue introduced in 6.3 with commit a5bf3cfce8cb and fixed in 6.7.2 with commit 5e23e283910c
	Issue introduced in 6.3 with commit a5bf3cfce8cb and fixed in 6.8 with commit bb57f6705960

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-2023-52455
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/iommu/of_iommu.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/98b8a550da83cc392a14298c4b3eaaf0332ae6ad
	https://git.kernel.org/stable/c/5e23e283910c9f30248732ae0770bcb0c9438abf
	https://git.kernel.org/stable/c/bb57f6705960bebeb832142ce9abf43220c3eab1