CVE-2026-97946: x86/amd_node: Fix PCI device reference counting in amd_smn_init()

CVE-2026-97946: x86/amd_node: Fix PCI device reference counting in amd_smn_init()

[Greg Kroah-Hartman]

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

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

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

x86/amd_node: Fix PCI device reference counting in amd_smn_init()

The local "root" pointer is a temporary variable used during the device
search. Therefore, refcount related to the search iterators should be cleaned
up after the search is complete.

Use the __free() cleanup macro to ensure the refcount is decremented when the
temporary pointer goes out of scope.

Additionally, increment the refcount when caching a root pointer. This ensures
the in-use refcount is separate from the temporary search refcounting.

Finally, drop the redundant "root = NULL" before the second search loop. The
pci_get_class() iterator always decrements the refcount of its "from"
argument, so the first loop can only fall through with "root" already NULL.

The Linux kernel CVE team has assigned CVE-2026-97946 to this issue.


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

	Issue introduced in 6.18 with commit 0a4b61d9c2e496b5f0a10e29e355a1465c8738bb and fixed in 6.18.53 with commit 84e3a71d11d8593c127b468d75b2653af5074f81
	Issue introduced in 6.18 with commit 0a4b61d9c2e496b5f0a10e29e355a1465c8738bb and fixed in 7.2.7 with commit aa2a4277ad42fd8f918c6dc652473946a253f7b0
	Issue introduced in 6.18 with commit 0a4b61d9c2e496b5f0a10e29e355a1465c8738bb and fixed in 7.3-rc4 with commit 27600805e62f800bacf990354632eae4e487d34c
	Issue introduced in 6.17.8 with commit c4ad899a33198ab6335732c769835d035e66894a

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-2026-97946
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:
	arch/x86/kernel/amd_node.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/84e3a71d11d8593c127b468d75b2653af5074f81
	https://git.kernel.org/stable/c/aa2a4277ad42fd8f918c6dc652473946a253f7b0
	https://git.kernel.org/stable/c/27600805e62f800bacf990354632eae4e487d34c