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, 94 insertions, 0 deletions

diff --git a/include/crypto/aes-xts.h b/include/crypto/aes-xts.h
new file mode 100644
index 000000000..b9e828265
--- /dev/null
+++ b/include/crypto/aes-xts.h
@@ -0,0 +1,94 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * AES-XTS unauthenticated encryption and decryption
+ *
+ * Copyright 2026 Google LLC
+ */
+#ifndef _CRYPTO_AES_XTS_H
+#define _CRYPTO_AES_XTS_H
+
+#include <crypto/aes.h>
+#include <crypto/xts.h>
+
+/**
+ * struct aes_xts_key - A key prepared for AES-XTS encryption and decryption
+ *
+ * Note that (depending on the architecture) this typically is around 768 bytes,
+ * which makes it a bit too large to allocate on the stack in most cases.
+ */
+struct aes_xts_key {
+	/* private: */
+	struct aes_key main_key;
+	struct aes_enckey tweak_key;
+};
+
+/**
+ * aes_xts_preparekey() - Prepare a key for AES-XTS encryption and decryption
+ * @key: (output) The key structure to initialize
+ * @in_key: The raw AES-XTS key
+ * @key_len: Length of the raw key in bytes
+ * @flags: Optional flag XTS_FORBID_WEAK_KEYS to forbid keys whose two halves
+ *	   are the same.
+ *
+ * Users should use memzero_explicit() to zeroize the key struct at the end of
+ * its lifetime.  (But if this function fails, zeroization is unnecessary.)
+ *
+ * Context: Any context.
+ * Return:
+ * * 0 on success
+ * * -EINVAL if the key is rejected because its length isn't 32, 64, or (when
+ *   FIPS mode isn't enabled) 48; or because its two halves are the same and
+ *   either XTS_FORBID_WEAK_KEYS is given or FIPS mode is enabled.
+ */
+int __must_check aes_xts_preparekey(struct aes_xts_key *key, const u8 *in_key,
+				    size_t key_len, int flags);
+
+/**
+ * aes_xts_encrypt() - Encrypt data using AES-XTS
+ * @dst: The destination buffer.  Can be in-place or out-of-place.  For other
+ *	 overlaps the behavior is unspecified.
+ * @src: The source data
+ * @len: Number of bytes to encrypt.  On non-final calls it must be a nonzero
+ *	 multiple of AES_BLOCK_SIZE.  On the final call it can be any value >=
+ *	 AES_BLOCK_SIZE, i.e. ciphertext stealing is supported.
+ * @tweak: The tweak.  It is updated with the next value, unless @len isn't a
+ *	   multiple of AES_BLOCK_SIZE in which case the value is unspecified.
+ * @key: The key, already prepared using aes_xts_preparekey()
+ * @cont: %false to begin encrypting a new message (do the tweak encryption);
+ *	  %true to continue encrypting a message (skip tweak encryption)
+ *
+ * This supports both one-shot and incremental encryption.  On the first call,
+ * pass @cont = %false.  On any later calls, pass @cont = %true and the updated
+ * @tweak; all earlier @len must have been multiples of AES_BLOCK_SIZE.
+ *
+ * Context: Any context.
+ */
+void aes_xts_encrypt(u8 *dst, const u8 *src, size_t len,
+		     u8 tweak[at_least AES_BLOCK_SIZE],
+		     const struct aes_xts_key *key, bool cont);
+
+/**
+ * aes_xts_decrypt() - Decrypt data using AES-XTS
+ * @dst: The destination buffer.  Can be in-place or out-of-place.  For other
+ *	 overlaps the behavior is unspecified.
+ * @src: The source data
+ * @len: Number of bytes to decrypt.  On non-final calls it must be a nonzero
+ *	 multiple of AES_BLOCK_SIZE.  On the final call it can be any value >=
+ *	 AES_BLOCK_SIZE, i.e. ciphertext stealing is supported.
+ * @tweak: The tweak.  It is updated with the next value, unless @len isn't a
+ *	   multiple of AES_BLOCK_SIZE in which case the value is unspecified.
+ * @key: The key, already prepared using aes_xts_preparekey()
+ * @cont: %false to begin decrypting a new message (do the tweak encryption);
+ *	  %true to continue decrypting a message (skip tweak encryption)
+ *
+ * This supports both one-shot and incremental decryption.  On the first call,
+ * pass @cont = %false.  On any later calls, pass @cont = %true and the updated
+ * @tweak; all earlier @len must have been multiples of AES_BLOCK_SIZE.
+ *
+ * Context: Any context.
+ */
+void aes_xts_decrypt(u8 *dst, const u8 *src, size_t len,
+		     u8 tweak[at_least AES_BLOCK_SIZE],
+		     const struct aes_xts_key *key, bool cont);
+
+#endif /* _CRYPTO_AES_XTS_H */