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, 43 insertions, 0 deletions

diff --git a/include/crypto/curve25519.h b/include/crypto/curve25519.h
new file mode 100644
index 000000000..2362b48f8
--- /dev/null
+++ b/include/crypto/curve25519.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
+/*
+ * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+#ifndef CURVE25519_H
+#define CURVE25519_H
+
+#include <linux/types.h>
+#include <linux/random.h>
+
+enum curve25519_lengths {
+	CURVE25519_KEY_SIZE = 32
+};
+
+void curve25519_generic(u8 out[at_least CURVE25519_KEY_SIZE],
+			const u8 scalar[at_least CURVE25519_KEY_SIZE],
+			const u8 point[at_least CURVE25519_KEY_SIZE]);
+
+bool __must_check
+curve25519(u8 mypublic[at_least CURVE25519_KEY_SIZE],
+	   const u8 secret[at_least CURVE25519_KEY_SIZE],
+	   const u8 basepoint[at_least CURVE25519_KEY_SIZE]);
+
+bool __must_check
+curve25519_generate_public(u8 pub[at_least CURVE25519_KEY_SIZE],
+			   const u8 secret[at_least CURVE25519_KEY_SIZE]);
+
+static inline void
+curve25519_clamp_secret(u8 secret[at_least CURVE25519_KEY_SIZE])
+{
+	secret[0] &= 248;
+	secret[31] = (secret[31] & 127) | 64;
+}
+
+static inline void
+curve25519_generate_secret(u8 secret[at_least CURVE25519_KEY_SIZE])
+{
+	get_random_bytes_wait(secret, CURVE25519_KEY_SIZE);
+	curve25519_clamp_secret(secret);
+}
+
+#endif /* CURVE25519_H */