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, 138 insertions, 0 deletions

diff --git a/samples/hid/hid_mouse.c b/samples/hid/hid_mouse.c
new file mode 100644
index 000000000..4b80d4e4c
--- /dev/null
+++ b/samples/hid/hid_mouse.c
@@ -0,0 +1,138 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (c) 2022 Benjamin Tissoires
+ *
+ * This is a pure HID-BPF example, and should be considered as such:
+ * on the Etekcity Scroll 6E, the X and Y axes will be swapped and
+ * inverted. On any other device... Not sure what this will do.
+ *
+ * This C main file is generic though. To adapt the code and test, users
+ * must amend only the .bpf.c file, which this program will load any
+ * eBPF program it finds.
+ */
+
+#include <assert.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <libgen.h>
+#include <signal.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/resource.h>
+#include <unistd.h>
+
+#include <linux/bpf.h>
+#include <linux/errno.h>
+
+#include <bpf/bpf.h>
+#include <bpf/libbpf.h>
+
+#include "hid_mouse.skel.h"
+
+static bool running = true;
+
+static void int_exit(int sig)
+{
+	running = false;
+	exit(0);
+}
+
+static void usage(const char *prog)
+{
+	fprintf(stderr,
+		"%s: %s /sys/bus/hid/devices/0BUS:0VID:0PID:00ID\n\n",
+		__func__, prog);
+	fprintf(stderr,
+		"This program will upload and attach a HID-BPF program to the given device.\n"
+		"On the Etekcity Scroll 6E, the X and Y axis will be inverted, but on any other\n"
+		"device, chances are high that the device will not be working anymore\n\n"
+		"consider this as a demo and adapt the eBPF program to your needs\n"
+		"Hit Ctrl-C to unbind the program and reset the device\n");
+}
+
+static int get_hid_id(const char *path)
+{
+	const char *str_id, *dir;
+	char uevent[1024];
+	int fd;
+
+	memset(uevent, 0, sizeof(uevent));
+	snprintf(uevent, sizeof(uevent) - 1, "%s/uevent", path);
+
+	fd = open(uevent, O_RDONLY | O_NONBLOCK);
+	if (fd < 0)
+		return -ENOENT;
+
+	close(fd);
+
+	dir = basename((char *)path);
+
+	str_id = dir + sizeof("0003:0001:0A37.");
+	return (int)strtol(str_id, NULL, 16);
+}
+
+int main(int argc, char **argv)
+{
+	struct hid_mouse *skel;
+	struct bpf_link *link;
+	int err;
+	const char *optstr = "";
+	const char *sysfs_path;
+	int opt, hid_id;
+
+	while ((opt = getopt(argc, argv, optstr)) != -1) {
+		switch (opt) {
+		default:
+			usage(basename(argv[0]));
+			return 1;
+		}
+	}
+
+	if (optind == argc) {
+		usage(basename(argv[0]));
+		return 1;
+	}
+
+	sysfs_path = argv[optind];
+	if (!sysfs_path) {
+		perror("sysfs");
+		return 1;
+	}
+
+	skel = hid_mouse__open();
+	if (!skel) {
+		fprintf(stderr, "%s  %s:%d", __func__, __FILE__, __LINE__);
+		return -1;
+	}
+
+	hid_id = get_hid_id(sysfs_path);
+
+	if (hid_id < 0) {
+		fprintf(stderr, "can not open HID device: %m\n");
+		return 1;
+	}
+	skel->struct_ops.mouse_invert->hid_id = hid_id;
+
+	err = hid_mouse__load(skel);
+	if (err < 0) {
+		fprintf(stderr, "can not load HID-BPF program: %m\n");
+		return 1;
+	}
+
+	link = bpf_map__attach_struct_ops(skel->maps.mouse_invert);
+	if (!link) {
+		fprintf(stderr, "can not attach HID-BPF program: %m\n");
+		return 1;
+	}
+
+	signal(SIGINT, int_exit);
+	signal(SIGTERM, int_exit);
+
+	while (running)
+		sleep(1);
+
+	hid_mouse__destroy(skel);
+
+	return 0;
+}