CVE-2026-64473: vfio: Remove device debugfs before releasing devres

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

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

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

vfio: Remove device debugfs before releasing devres

VFIO device debugfs files created with debugfs_create_devm_seqfile()
store a devres allocated debugfs_devm_entry as inode private data.
vfio_unregister_group_dev() currently calls vfio_device_del() before
vfio_device_debugfs_exit(), but device_del() releases devres.  This can
leave debugfs entries visible with stale inode private data while
unregister waits for userspace references to drain.

Remove the per-device debugfs tree before vfio_device_del().  The debugfs
view is diagnostic only, so losing it at the start of unregister is
preferable to preserving entries whose backing storage may already have
been released.

Complete the teardown by clearing the per-device debugfs root after
removal.  This matches the global debugfs root cleanup and prevents
future users from mistaking a removed dentry for a live debugfs tree
during the remainder of unregister.

The Linux kernel CVE team has assigned CVE-2026-64473 to this issue.


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

	Issue introduced in 6.8 with commit 2202844e4468c7539dba0c0b06577c93735af952 and fixed in 6.12.96 with commit 6cc60b41d61657dc469893d14e8e55d160056ff1
	Issue introduced in 6.8 with commit 2202844e4468c7539dba0c0b06577c93735af952 and fixed in 6.18.39 with commit a53109ffb6b5148e11a27fb7670355b92db12dd3
	Issue introduced in 6.8 with commit 2202844e4468c7539dba0c0b06577c93735af952 and fixed in 7.1.4 with commit a5df401dc84f091e20b045560569f0736758fea7
	Issue introduced in 6.8 with commit 2202844e4468c7539dba0c0b06577c93735af952 and fixed in 7.2-rc2 with commit dc7fe87de492ea7f33a72b78d26650b75bf37f4f

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-2026-64473
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/vfio/debugfs.c
	drivers/vfio/vfio_main.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/6cc60b41d61657dc469893d14e8e55d160056ff1
	https://git.kernel.org/stable/c/a53109ffb6b5148e11a27fb7670355b92db12dd3
	https://git.kernel.org/stable/c/a5df401dc84f091e20b045560569f0736758fea7
	https://git.kernel.org/stable/c/dc7fe87de492ea7f33a72b78d26650b75bf37f4f