From patchwork Thu Jan 20 07:12:11 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 12718346 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 63911C433F5 for ; Thu, 20 Jan 2022 07:16:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1358951AbiATHQT (ORCPT ); Thu, 20 Jan 2022 02:16:19 -0500 Received: from ams.source.kernel.org ([145.40.68.75]:52854 "EHLO ams.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229496AbiATHQR (ORCPT ); Thu, 20 Jan 2022 02:16:17 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id E0500B81902; Thu, 20 Jan 2022 07:16:15 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3B7C0C340E9; Thu, 20 Jan 2022 07:16:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1642662974; bh=AisQShPpFV3Eliyeb/P+Zfoyyi9GVLa7kPFiEZALl0g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=IHAvIpo1+755z5fv7ooM7Nesr4mQJSyaBUqw8X6GRahDTVAr1bAMg5yTVoE+3z8Xq Eb2PU+2Mq4r6EUCZayEIC7VKcw/9UJovPV8pt1f/K2jRVa2KGSTYVmzUdS/RZw7mdX NDUz3XkTnhsSfwHJWuuctR3i9DPzzEd9x8KhMwD9b/uerU6kCSD5NO/RN8satfzmQ6 u+NF61eQFHva2iPADFlVLnjoSQ1G4/z1HBfUexL8UPjIuDC7xcj4zFcSAeBoxbdTN8 YeNlqI95xW6mPlzucXxAdGclB62r0wc/TyJSDNeyawGapMu4LwmbAIwBl8qA1x60fI ZFUpTsHtfOIGA== From: Eric Biggers To: linux-fscrypt@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-xfs@vger.kernel.org, Christoph Hellwig , Dave Chinner , "Darrick J . Wong" , Theodore Ts'o , Jaegeuk Kim , Chao Yu , Satya Tangirala Subject: [PATCH v10 1/5] fscrypt: add functions for direct I/O support Date: Wed, 19 Jan 2022 23:12:11 -0800 Message-Id: <20220120071215.123274-2-ebiggers@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220120071215.123274-1-ebiggers@kernel.org> References: <20220120071215.123274-1-ebiggers@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org From: Eric Biggers Encrypted files traditionally haven't supported DIO, due to the need to encrypt/decrypt the data. However, when the encryption is implemented using inline encryption (blk-crypto) instead of the traditional filesystem-layer encryption, it is straightforward to support DIO. In preparation for supporting this, add the following functions: - fscrypt_dio_unsupported() checks whether a DIO request is unsupported due to encryption constraints. Encrypted files will only support DIO when inline encryption is used and the I/O request is properly aligned; this function checks these preconditions. - fscrypt_limit_io_blocks() limits the length of a bio to avoid crossing a place in the file that a bio with an encryption context cannot cross due to a DUN discontiguity. This function is needed by filesystems that use the iomap DIO implementation (which operates directly on logical ranges, so it won't use fscrypt_mergeable_bio()) and that support FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32. Co-developed-by: Satya Tangirala Signed-off-by: Satya Tangirala Signed-off-by: Eric Biggers --- fs/crypto/crypto.c | 8 ++++ fs/crypto/inline_crypt.c | 90 ++++++++++++++++++++++++++++++++++++++++ include/linux/fscrypt.h | 18 ++++++++ 3 files changed, 116 insertions(+) diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c index 4ef3f714046aa..4fcca79f39aeb 100644 --- a/fs/crypto/crypto.c +++ b/fs/crypto/crypto.c @@ -69,6 +69,14 @@ void fscrypt_free_bounce_page(struct page *bounce_page) } EXPORT_SYMBOL(fscrypt_free_bounce_page); +/* + * Generate the IV for the given logical block number within the given file. + * For filenames encryption, lblk_num == 0. + * + * Keep this in sync with fscrypt_limit_io_blocks(). fscrypt_limit_io_blocks() + * needs to know about any IV generation methods where the low bits of IV don't + * simply contain the lblk_num (e.g., IV_INO_LBLK_32). + */ void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num, const struct fscrypt_info *ci) { diff --git a/fs/crypto/inline_crypt.c b/fs/crypto/inline_crypt.c index c57bebfa48fea..304ae414cbbf2 100644 --- a/fs/crypto/inline_crypt.c +++ b/fs/crypto/inline_crypt.c @@ -17,6 +17,7 @@ #include #include #include +#include #include "fscrypt_private.h" @@ -315,6 +316,10 @@ EXPORT_SYMBOL_GPL(fscrypt_set_bio_crypt_ctx_bh); * * fscrypt_set_bio_crypt_ctx() must have already been called on the bio. * + * This function isn't required in cases where crypto-mergeability is ensured in + * another way, such as I/O targeting only a single file (and thus a single key) + * combined with fscrypt_limit_io_blocks() to ensure DUN contiguity. + * * Return: true iff the I/O is mergeable */ bool fscrypt_mergeable_bio(struct bio *bio, const struct inode *inode, @@ -363,3 +368,88 @@ bool fscrypt_mergeable_bio_bh(struct bio *bio, return fscrypt_mergeable_bio(bio, inode, next_lblk); } EXPORT_SYMBOL_GPL(fscrypt_mergeable_bio_bh); + +/** + * fscrypt_dio_unsupported() - check whether a DIO (direct I/O) request is + * unsupported due to encryption constraints + * @iocb: the file and position the I/O is targeting + * @iter: the I/O data segment(s) + * + * Return: true if DIO is unsupported + */ +bool fscrypt_dio_unsupported(struct kiocb *iocb, struct iov_iter *iter) +{ + const struct inode *inode = file_inode(iocb->ki_filp); + const unsigned int blocksize = i_blocksize(inode); + + /* If the file is unencrypted, no veto from us. */ + if (!fscrypt_needs_contents_encryption(inode)) + return false; + + /* We only support DIO with inline crypto, not fs-layer crypto. */ + if (!fscrypt_inode_uses_inline_crypto(inode)) + return true; + + /* + * Since the granularity of encryption is filesystem blocks, the file + * position and total I/O length must be aligned to the filesystem block + * size -- not just to the block device's logical block size as is + * traditionally the case for DIO on many filesystems (not including + * f2fs, which only allows filesystem block aligned DIO anyway). + * + * We also require that the user-provided memory buffers be block + * aligned too. It is simpler to have a single alignment value required + * for all properties of the I/O, as is normally the case for DIO. + * Also, allowing less aligned buffers would also imply that a data unit + * could cross bvecs, which would greatly complicate the I/O stack, + * which assumes that bios can be split at any bvec boundary. + */ + if (!IS_ALIGNED(iocb->ki_pos | iov_iter_alignment(iter), blocksize)) + return true; + + return false; +} +EXPORT_SYMBOL_GPL(fscrypt_dio_unsupported); + +/** + * fscrypt_limit_io_blocks() - limit I/O blocks to avoid discontiguous DUNs + * @inode: the file on which I/O is being done + * @lblk: the block at which the I/O is being started from + * @nr_blocks: the number of blocks we want to submit starting at @lblk + * + * Determine the limit to the number of blocks that can be submitted in a bio + * targeting @lblk without causing a data unit number (DUN) discontiguity. + * + * This is normally just @nr_blocks, as normally the DUNs just increment along + * with the logical blocks. (Or the file is not encrypted.) + * + * In rare cases, fscrypt can be using an IV generation method that allows the + * DUN to wrap around within logically contiguous blocks, and that wraparound + * will occur. If this happens, a value less than @nr_blocks will be returned + * so that the wraparound doesn't occur in the middle of a bio, which would + * cause encryption/decryption to produce the wrong results. + * + * Return: the actual number of blocks that can be submitted + */ +u64 fscrypt_limit_io_blocks(const struct inode *inode, u64 lblk, u64 nr_blocks) +{ + const struct fscrypt_info *ci = inode->i_crypt_info; + u32 dun; + + if (!fscrypt_inode_uses_inline_crypto(inode)) + return nr_blocks; + + if (nr_blocks <= 1) + return nr_blocks; + + if (!(fscrypt_policy_flags(&ci->ci_policy) & + FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32)) + return nr_blocks; + + /* With IV_INO_LBLK_32, the DUN can wrap around from U32_MAX to 0. */ + + dun = ci->ci_hashed_ino + lblk; + + return min_t(u64, nr_blocks, (u64)U32_MAX + 1 - dun); +} +EXPORT_SYMBOL_GPL(fscrypt_limit_io_blocks); diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h index 91ea9477e9bd2..87ec5f63b0a82 100644 --- a/include/linux/fscrypt.h +++ b/include/linux/fscrypt.h @@ -714,6 +714,10 @@ bool fscrypt_mergeable_bio(struct bio *bio, const struct inode *inode, bool fscrypt_mergeable_bio_bh(struct bio *bio, const struct buffer_head *next_bh); +bool fscrypt_dio_unsupported(struct kiocb *iocb, struct iov_iter *iter); + +u64 fscrypt_limit_io_blocks(const struct inode *inode, u64 lblk, u64 nr_blocks); + #else /* CONFIG_FS_ENCRYPTION_INLINE_CRYPT */ static inline bool __fscrypt_inode_uses_inline_crypto(const struct inode *inode) @@ -742,6 +746,20 @@ static inline bool fscrypt_mergeable_bio_bh(struct bio *bio, { return true; } + +static inline bool fscrypt_dio_unsupported(struct kiocb *iocb, + struct iov_iter *iter) +{ + const struct inode *inode = file_inode(iocb->ki_filp); + + return fscrypt_needs_contents_encryption(inode); +} + +static inline u64 fscrypt_limit_io_blocks(const struct inode *inode, u64 lblk, + u64 nr_blocks) +{ + return nr_blocks; +} #endif /* !CONFIG_FS_ENCRYPTION_INLINE_CRYPT */ /**