CVE-2026-89447: iommufd: Avoid locking internal accesses during unmap

CVE-2026-89447: iommufd: Avoid locking internal accesses during unmap

[Greg Kroah-Hartman]

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

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

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

iommufd: Avoid locking internal accesses during unmap

iommufd_access_notify_unmap() skips internal accesses because they do
not have an external unmap callback to invoke.

However, the current test calls iommufd_lock_obj() before checking
whether the access is internal. If iommufd_lock_obj() succeeds, the loop
then sees the internal access and continues, bypassing the matching
iommufd_put_object() used by the normal unmap path. This leaks the
object reference taken by iommufd_lock_obj().

Check for internal accesses first so skipped entries are never locked.

The Linux kernel CVE team has assigned CVE-2026-89447 to this issue.


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

	Issue introduced in 6.17 with commit 27b77ea5feaa8fcf385ea99ce757982b0ac9d1f0 and fixed in 6.18.50 with commit 436189ee4bb2c7c993b945d68570dd38c3e4349e
	Issue introduced in 6.17 with commit 27b77ea5feaa8fcf385ea99ce757982b0ac9d1f0 and fixed in 7.2.4 with commit 50a66a63d1c841ae6b28a4551f642c1bba4c9529
	Issue introduced in 6.17 with commit 27b77ea5feaa8fcf385ea99ce757982b0ac9d1f0 and fixed in 7.3-rc1 with commit 0dbcdf4473a614adbd732d567c9b39ac0e040e0c

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-2026-89447
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/iommufd/device.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/436189ee4bb2c7c993b945d68570dd38c3e4349e
	https://git.kernel.org/stable/c/50a66a63d1c841ae6b28a4551f642c1bba4c9529
	https://git.kernel.org/stable/c/0dbcdf4473a614adbd732d567c9b39ac0e040e0c