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, 82 insertions, 0 deletions

diff --git a/lib/crypto/nh.c b/lib/crypto/nh.c
new file mode 100644
index 000000000..e1d0095b5
--- /dev/null
+++ b/lib/crypto/nh.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2018 Google LLC
+ */
+
+/*
+ * Implementation of the NH almost-universal hash function, specifically the
+ * variant of NH used in Adiantum.  This is *not* a cryptographic hash function.
+ *
+ * Reference: section 6.3 of "Adiantum: length-preserving encryption for
+ * entry-level processors" (https://eprint.iacr.org/2018/720.pdf).
+ */
+
+#include <crypto/nh.h>
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/unaligned.h>
+
+#ifdef CONFIG_CRYPTO_LIB_NH_ARCH
+#include "nh.h" /* $(SRCARCH)/nh.h */
+#else
+static bool nh_arch(const u32 *key, const u8 *message, size_t message_len,
+		    __le64 hash[NH_NUM_PASSES])
+{
+	return false;
+}
+#endif
+
+void nh(const u32 *key, const u8 *message, size_t message_len,
+	__le64 hash[NH_NUM_PASSES])
+{
+	u64 sums[4] = { 0, 0, 0, 0 };
+
+	if (nh_arch(key, message, message_len, hash))
+		return;
+
+	static_assert(NH_PAIR_STRIDE == 2);
+	static_assert(NH_NUM_PASSES == 4);
+
+	while (message_len) {
+		u32 m0 = get_unaligned_le32(message + 0);
+		u32 m1 = get_unaligned_le32(message + 4);
+		u32 m2 = get_unaligned_le32(message + 8);
+		u32 m3 = get_unaligned_le32(message + 12);
+
+		sums[0] += (u64)(u32)(m0 + key[0]) * (u32)(m2 + key[2]);
+		sums[1] += (u64)(u32)(m0 + key[4]) * (u32)(m2 + key[6]);
+		sums[2] += (u64)(u32)(m0 + key[8]) * (u32)(m2 + key[10]);
+		sums[3] += (u64)(u32)(m0 + key[12]) * (u32)(m2 + key[14]);
+		sums[0] += (u64)(u32)(m1 + key[1]) * (u32)(m3 + key[3]);
+		sums[1] += (u64)(u32)(m1 + key[5]) * (u32)(m3 + key[7]);
+		sums[2] += (u64)(u32)(m1 + key[9]) * (u32)(m3 + key[11]);
+		sums[3] += (u64)(u32)(m1 + key[13]) * (u32)(m3 + key[15]);
+		key += NH_MESSAGE_UNIT / sizeof(key[0]);
+		message += NH_MESSAGE_UNIT;
+		message_len -= NH_MESSAGE_UNIT;
+	}
+
+	hash[0] = cpu_to_le64(sums[0]);
+	hash[1] = cpu_to_le64(sums[1]);
+	hash[2] = cpu_to_le64(sums[2]);
+	hash[3] = cpu_to_le64(sums[3]);
+}
+EXPORT_SYMBOL_GPL(nh);
+
+#ifdef nh_mod_init_arch
+static int __init nh_mod_init(void)
+{
+	nh_mod_init_arch();
+	return 0;
+}
+subsys_initcall(nh_mod_init);
+
+static void __exit nh_mod_exit(void)
+{
+}
+module_exit(nh_mod_exit);
+#endif
+
+MODULE_DESCRIPTION("NH almost-universal hash function");
+MODULE_LICENSE("GPL");