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

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.

Fixes: 0a4b61d9c2e4 ("x86/amd_node: Fix AMD root device caching")
Closes: https://sashiko.dev/#/patchset/20260806160159.230453-1-jason.andryuk%40amd.com
Reported-by: Sashiko <sashiko-bot@kernel.org>
Assisted-by: LLM
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/20260903154325.74343-1-yazen.ghannam@amd.com

1 files changed, 51 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-uevent b/Documentation/ABI/testing/sysfs-uevent
new file mode 100644
index 000000000..c15e18c47
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-uevent
@@ -0,0 +1,51 @@
+What:           /sys/.../uevent
+Date:           May 2017
+KernelVersion:  4.13
+Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
+Description:
+                Enable passing additional variables for synthetic uevents that
+                are generated by writing /sys/.../uevent file.
+
+                Recognized extended format is::
+
+			ACTION [UUID [KEY=VALUE ...]]
+
+                The ACTION is compulsory - it is the name of the uevent
+                action (``add``, ``change``, ``remove``). There is no change
+                compared to previous functionality here. The rest of the
+                extended format is optional.
+
+                You need to pass UUID first before any KEY=VALUE pairs.
+                The UUID must be in ``xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx``
+                format where 'x' is a hex digit. The UUID is considered to be
+                a transaction identifier so it's possible to use the same UUID
+                value for one or more synthetic uevents in which case we
+                logically group these uevents together for any userspace
+                listeners. The UUID value appears in uevent as
+                ``SYNTH_UUID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx`` environment
+                variable.
+
+                If UUID is not passed in, the generated synthetic uevent gains
+                ``SYNTH_UUID=0`` environment variable automatically.
+
+                The KEY=VALUE pairs can contain alphanumeric characters only.
+
+                It's possible to define zero or more pairs - each pair is then
+                delimited by a space character ' '. Each pair appears in
+                synthetic uevent as ``SYNTH_ARG_KEY=VALUE``. That means the KEY
+                name gains ``SYNTH_ARG_`` prefix to avoid possible collisions
+                with existing variables.
+
+                Example of valid sequence written to the uevent file::
+
+                    add fe4d7c9d-b8c6-4a70-9ef1-3d8a58d18eed A=1 B=abc
+
+                This generates synthetic uevent including these variables::
+
+                    ACTION=add
+                    SYNTH_ARG_A=1
+                    SYNTH_ARG_B=abc
+                    SYNTH_UUID=fe4d7c9d-b8c6-4a70-9ef1-3d8a58d18eed
+
+Users:
+                udev, userspace tools generating synthetic uevents