CVE-2026-74355: iommu/vt-d: Fix RB-tree corruption in probe error path

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

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

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

iommu/vt-d: Fix RB-tree corruption in probe error path

The info->node RB-tree member is zero-initialized via kzalloc. If
a device does not support ATS, the device_rbtree_insert() call is
skipped. If a subsequent probe step fails, the error path jumps to
device_rbtree_remove(), which misinterprets the zeroed node as
a tree root and corrupts the device RB-tree.

Fix this by explicitly initializing the RB-node as empty using
RB_CLEAR_NODE() during initialization and guarding the removal with
RB_EMPTY_NODE().

The Linux kernel CVE team has assigned CVE-2026-74355 to this issue.


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

	Issue introduced in 6.15 with commit 4f1492efb495bcef34c9ee8a94af81e6cea5abf4 and fixed in 6.18.40 with commit f5102e0fc3c6dc8685549891a96e4589fdb3e211
	Issue introduced in 6.15 with commit 4f1492efb495bcef34c9ee8a94af81e6cea5abf4 and fixed in 7.1.5 with commit d16923a45d4d08367650fdc3451c89299ab6ac5a
	Issue introduced in 6.15 with commit 4f1492efb495bcef34c9ee8a94af81e6cea5abf4 and fixed in 7.2-rc1 with commit 43bd9e6d5513cb1edbafdeef146a1edc3aaced56

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-2026-74355
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/intel/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/f5102e0fc3c6dc8685549891a96e4589fdb3e211
	https://git.kernel.org/stable/c/d16923a45d4d08367650fdc3451c89299ab6ac5a
	https://git.kernel.org/stable/c/43bd9e6d5513cb1edbafdeef146a1edc3aaced56