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, 78 insertions, 0 deletions

diff --git a/lib/crypto/curve25519.c b/lib/crypto/curve25519.c
new file mode 100644
index 000000000..01e265dfb
--- /dev/null
+++ b/lib/crypto/curve25519.c
@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+/*
+ * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ *
+ * This is an implementation of the Curve25519 ECDH algorithm, using either an
+ * architecture-optimized implementation or a generic implementation. The
+ * generic implementation is either 32-bit, or 64-bit with 128-bit integers,
+ * depending on what is supported by the target compiler.
+ *
+ * Information: https://cr.yp.to/ecdh.html
+ */
+
+#include <crypto/curve25519.h>
+#include <crypto/utils.h>
+#include <linux/export.h>
+#include <linux/init.h>
+#include <linux/module.h>
+
+static const u8 curve25519_null_point[CURVE25519_KEY_SIZE] __aligned(32) = { 0 };
+static const u8 curve25519_base_point[CURVE25519_KEY_SIZE] __aligned(32) = { 9 };
+
+#ifdef CONFIG_CRYPTO_LIB_CURVE25519_ARCH
+#include "curve25519.h" /* $(SRCARCH)/curve25519.h */
+#else
+static void curve25519_arch(u8 mypublic[CURVE25519_KEY_SIZE],
+			    const u8 secret[CURVE25519_KEY_SIZE],
+			    const u8 basepoint[CURVE25519_KEY_SIZE])
+{
+	curve25519_generic(mypublic, secret, basepoint);
+}
+
+static void curve25519_base_arch(u8 pub[CURVE25519_KEY_SIZE],
+				 const u8 secret[CURVE25519_KEY_SIZE])
+{
+	curve25519_generic(pub, secret, curve25519_base_point);
+}
+#endif
+
+bool __must_check
+curve25519(u8 mypublic[CURVE25519_KEY_SIZE],
+	   const u8 secret[CURVE25519_KEY_SIZE],
+	   const u8 basepoint[CURVE25519_KEY_SIZE])
+{
+	curve25519_arch(mypublic, secret, basepoint);
+	return crypto_memneq(mypublic, curve25519_null_point,
+			     CURVE25519_KEY_SIZE);
+}
+EXPORT_SYMBOL(curve25519);
+
+bool __must_check
+curve25519_generate_public(u8 pub[CURVE25519_KEY_SIZE],
+			   const u8 secret[CURVE25519_KEY_SIZE])
+{
+	if (unlikely(!crypto_memneq(secret, curve25519_null_point,
+				    CURVE25519_KEY_SIZE)))
+		return false;
+	curve25519_base_arch(pub, secret);
+	return crypto_memneq(pub, curve25519_null_point, CURVE25519_KEY_SIZE);
+}
+EXPORT_SYMBOL(curve25519_generate_public);
+
+#ifdef curve25519_mod_init_arch
+static int __init curve25519_mod_init(void)
+{
+	curve25519_mod_init_arch();
+	return 0;
+}
+subsys_initcall(curve25519_mod_init);
+
+static void __exit curve25519_mod_exit(void)
+{
+}
+module_exit(curve25519_mod_exit);
+#endif
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Curve25519 algorithm");
+MODULE_AUTHOR("Jason A. Donenfeld <Jason@zx2c4.com>");