CVE-2026-80894: iommufd: Fix wrong hwpt passed to iommufd_auto_response_faults on replace

CVE-2026-80894: iommufd: Fix wrong hwpt passed to iommufd_auto_response_faults on replace

[Greg Kroah-Hartman]

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

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

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

iommufd: Fix wrong hwpt passed to iommufd_auto_response_faults on replace

iommufd_hwpt_replace_device() calls:

	iommufd_auto_response_faults(hwpt, old_handle);

passing the *new* hwpt together with the handle of
the device's *old* domain. This should be a parameter mismatch:

1. Semantically, iommufd_auto_response_faults(x, handle) scans
   x->fault's deliver list and response xarray for groups matching
   "handle". A group is queued under the hwpt that was attached at
   fault-delivery time. old_handle is fetched *before* the domain switch,
   so its group lives on old->fault, not on the new hwpt->fault.

2. Historically, the first argument was "old". The routine was
   introduced by commit b7d8833677ba ("iommufd: Fault-capable hwpt
   attach/detach/replace") as __fault_domain_replace_dev() in
   fault.c, correctly calling iommufd_auto_response_faults(old, curr).
   Commit fb21b1568ada ("iommufd: Make attach_handle generic than
   fault specific") moved this into iommufd_hwpt_replace_device() in
   device.c and swapped it to "hwpt". This should be a refactor regression,
   not an intentional change.

Fix this by passing "old" instead.

The Linux kernel CVE team has assigned CVE-2026-80894 to this issue.


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

	Issue introduced in 6.12.24 with commit 6d11543bf37abdf60b8e6022a62fccfb82a5fe2e and fixed in 6.12.105 with commit adb87155b67f9759ff010c0a99559f5bffa45dcf
	Issue introduced in 6.15 with commit fb21b1568adaa76af7a8c853f37c60fba8b28661 and fixed in 6.18.44 with commit 564ac339c0f8bada4e77a57a92bab9d3df635e07
	Issue introduced in 6.15 with commit fb21b1568adaa76af7a8c853f37c60fba8b28661 and fixed in 7.1.8 with commit 8eb077025279304268bd58657f0af3d388822b21
	Issue introduced in 6.15 with commit fb21b1568adaa76af7a8c853f37c60fba8b28661 and fixed in 7.2 with commit ba5c0f28a26e7d9be1e0997f8920dd638e2782fd
	Issue introduced in 6.13.12 with commit 1e0216b6a58c79b5ee91c78706d5f560e4d1f56f
	Issue introduced in 6.14.3 with commit 4b23c4b991eb90cc7bca42e9f81142feedd4bb56

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-2026-80894
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/adb87155b67f9759ff010c0a99559f5bffa45dcf
	https://git.kernel.org/stable/c/564ac339c0f8bada4e77a57a92bab9d3df635e07
	https://git.kernel.org/stable/c/8eb077025279304268bd58657f0af3d388822b21
	https://git.kernel.org/stable/c/ba5c0f28a26e7d9be1e0997f8920dd638e2782fd