From dd05add7b2b6004c5fa3a1f276f56d8668f86b65 Mon Sep 17 00:00:00 2001 From: Paulo Alcantara Date: Sat, 26 Sep 2026 19:20:30 -0300 Subject: netfs: zero the tail of a short DIO/unbuffered read The buffered read collector zero-fills the tail of a short read that stops below the inode's i_size (netfs_clear_unread()), so a read that races an extending write still returns the expected number of bytes. The non-buffered collector path does no such thing: it just records how much was transferred. Add the same zero-fill for the non-buffered case, gated on NETFS_SREQ_CLEAR_TAIL: a subreq's source sets that flag when a short result from it is known to be safe to treat as a hole, as opposed to NETFS_SREQ_HIT_EOF, which means the read genuinely ran off the end of the file and should be reported short as-is. Only CLEAR_TAIL should zero-fill here; a real EOF must stay a real short read. No source currently sets CLEAR_TAIL on an unbuffered/DIO subrequest, so this is inert on its own -- a following change teaches cifs to set it in the one case that needs it. Fixes: e2d46f2ec332 ("netfs: Change the read result collector to only use one work item") Reviewed-by: David Howells Reviewed-by: Namjae Jeon Signed-off-by: Paulo Alcantara Cc: Christian Brauner Cc: Matthew Wilcox Cc: Ronnie Sahlberg Cc: Shyam Prasad N Cc: Tom Talpey Cc: Bharath SM Cc: stable@vger.kernel.org --- include/crypto/aes-ctr.h | 65 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 65 insertions(+) create mode 100644 include/crypto/aes-ctr.h (limited to 'include/crypto/aes-ctr.h') diff --git a/include/crypto/aes-ctr.h b/include/crypto/aes-ctr.h new file mode 100644 index 000000000..8e214a857 --- /dev/null +++ b/include/crypto/aes-ctr.h @@ -0,0 +1,65 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * AES-CTR and AES-XCTR stream ciphers + * + * Copyright 2026 Google LLC + */ +#ifndef _CRYPTO_AES_CTR_H +#define _CRYPTO_AES_CTR_H + +#include + +/** + * aes_ctr() - AES-CTR en/decryption + * @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 en/decrypt + * @ctr: The counter. It will be incremented by ceil(@len / AES_BLOCK_SIZE). + * @key: The key, already prepared using aes_preparekey() or aes_prepareenckey() + * + * This implements AES in counter mode with a 128-bit big endian counter. + * + * This exists only for use by the implementation of modes built on top of CTR + * (e.g., GCM and CCM) and some legacy protocols that use CTR mode directly. + * Callers are expected to know how to use CTR mode appropriately, including + * choosing (key, counter) pairs appropriately to avoid keystream reuse. + * + * This supports incremental en/decryption. The length of each non-final chunk + * must be a multiple of AES_BLOCK_SIZE, and the updated @ctr must be passed in + * each time. + * + * Context: Any context. + */ +void aes_ctr(u8 *dst, const u8 *src, size_t len, + u8 ctr[at_least AES_BLOCK_SIZE], aes_encrypt_arg key); + +/** + * aes_xctr() - AES-XCTR en/decryption + * @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 en/decrypt + * @ctr: The block counter (in host endianness). For the first call, set it to + * 1. It will be incremented by ceil(@len / AES_BLOCK_SIZE). + * @iv: The initialization vector + * @key: The key, already prepared using aes_preparekey() or aes_prepareenckey() + * + * This implements AES in XOR Counter mode, as specified in the paper + * "Length-preserving encryption with HCTR2" + * (https://eprint.iacr.org/2021/1441.pdf). + * + * This exists only for use by the implementation of modes built on top of XCTR. + * Callers are expected to know how to use XCTR mode appropriately, including + * choosing (key, IV) pairs appropriately to avoid keystream reuse. + * + * This supports incremental en/decryption. The length of each non-final chunk + * must be a multiple of AES_BLOCK_SIZE, and the updated @ctr must be passed in + * each time. + * + * Context: Any context. + */ +void aes_xctr(u8 *dst, const u8 *src, size_t len, u64 *ctr, + const u8 iv[at_least AES_BLOCK_SIZE], aes_encrypt_arg key); + +#endif /* _CRYPTO_AES_CTR_H */ -- cgit v1.3.1