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, 32 insertions, 0 deletions

diff --git a/rust/helpers/device.c b/rust/helpers/device.c
new file mode 100644
index 000000000..3be4ee590
--- /dev/null
+++ b/rust/helpers/device.c
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/device.h>
+
+__rust_helper int rust_helper_devm_add_action(struct device *dev,
+					      void (*action)(void *),
+					      void *data)
+{
+	return devm_add_action(dev, action, data);
+}
+
+__rust_helper int rust_helper_devm_add_action_or_reset(struct device *dev,
+						       void (*action)(void *),
+						       void *data)
+{
+	return devm_add_action_or_reset(dev, action, data);
+}
+
+__rust_helper void *rust_helper_dev_get_drvdata(const struct device *dev)
+{
+	return dev_get_drvdata(dev);
+}
+
+__rust_helper void rust_helper_dev_set_drvdata(struct device *dev, void *data)
+{
+	dev_set_drvdata(dev, data);
+}
+
+__rust_helper const char *rust_helper_dev_name(const struct device *dev)
+{
+	return dev_name(dev);
+}