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, 90 insertions, 0 deletions

diff --git a/net/ipv4/metrics.c b/net/ipv4/metrics.c
new file mode 100644
index 000000000..ad40762a8
--- /dev/null
+++ b/net/ipv4/metrics.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/netlink.h>
+#include <linux/nospec.h>
+#include <linux/rtnetlink.h>
+#include <linux/types.h>
+#include <net/ip.h>
+#include <net/net_namespace.h>
+#include <net/tcp.h>
+
+static int ip_metrics_convert(struct nlattr *fc_mx,
+			      int fc_mx_len, u32 *metrics,
+			      struct netlink_ext_ack *extack)
+{
+	bool ecn_ca = false;
+	struct nlattr *nla;
+	int remaining;
+
+	nla_for_each_attr(nla, fc_mx, fc_mx_len, remaining) {
+		int type = nla_type(nla);
+		u32 val;
+
+		if (!type)
+			continue;
+		if (type > RTAX_MAX) {
+			NL_SET_ERR_MSG(extack, "Invalid metric type");
+			return -EINVAL;
+		}
+
+		type = array_index_nospec(type, RTAX_MAX + 1);
+		if (type == RTAX_CC_ALGO) {
+			char tmp[TCP_CA_NAME_MAX];
+
+			nla_strscpy(tmp, nla, sizeof(tmp));
+			val = tcp_ca_get_key_by_name(tmp, &ecn_ca);
+			if (val == TCP_CA_UNSPEC) {
+				NL_SET_ERR_MSG(extack, "Unknown tcp congestion algorithm");
+				return -EINVAL;
+			}
+		} else {
+			if (nla_len(nla) != sizeof(u32)) {
+				NL_SET_ERR_MSG_ATTR(extack, nla,
+						    "Invalid attribute in metrics");
+				return -EINVAL;
+			}
+			val = nla_get_u32(nla);
+		}
+		if (type == RTAX_ADVMSS && val > 65535 - 40)
+			val = 65535 - 40;
+		if (type == RTAX_MTU && val > 65535 - 15)
+			val = 65535 - 15;
+		if (type == RTAX_HOPLIMIT && val > 255)
+			val = 255;
+		if (type == RTAX_FEATURES && (val & ~RTAX_FEATURE_MASK)) {
+			NL_SET_ERR_MSG(extack, "Unknown flag set in feature mask in metrics attribute");
+			return -EINVAL;
+		}
+		metrics[type - 1] = val;
+	}
+
+	if (ecn_ca)
+		metrics[RTAX_FEATURES - 1] |= DST_FEATURE_ECN_CA;
+
+	return 0;
+}
+
+struct dst_metrics *ip_fib_metrics_init(struct nlattr *fc_mx,
+					int fc_mx_len,
+					struct netlink_ext_ack *extack)
+{
+	struct dst_metrics *fib_metrics;
+	int err;
+
+	if (!fc_mx)
+		return (struct dst_metrics *)&dst_default_metrics;
+
+	fib_metrics = kzalloc_obj(*fib_metrics);
+	if (unlikely(!fib_metrics))
+		return ERR_PTR(-ENOMEM);
+
+	err = ip_metrics_convert(fc_mx, fc_mx_len, fib_metrics->metrics,
+				 extack);
+	if (!err) {
+		refcount_set(&fib_metrics->refcnt, 1);
+	} else {
+		kfree(fib_metrics);
+		fib_metrics = ERR_PTR(err);
+	}
+
+	return fib_metrics;
+}