diff options
Diffstat (limited to 'fs/crypto')
| -rw-r--r-- | fs/crypto/crypto.c | 8 | ||||
| -rw-r--r-- | fs/crypto/inline_crypt.c | 93 |
2 files changed, 101 insertions, 0 deletions
diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c index 4ef3f714046a..4fcca79f39ae 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 c57bebfa48fe..93c2ca858092 100644 --- a/fs/crypto/inline_crypt.c +++ b/fs/crypto/inline_crypt.c @@ -17,6 +17,7 @@ #include <linux/buffer_head.h> #include <linux/sched/mm.h> #include <linux/slab.h> +#include <linux/uio.h> #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 +368,91 @@ 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_supported() - check whether a DIO (direct I/O) request is + * supported as far as encryption is concerned + * @iocb: the file and position the I/O is targeting + * @iter: the I/O data segment(s) + * + * Return: %true if there are no encryption constraints that prevent DIO from + * being supported; %false if DIO is unsupported. (Note that in the + * %true case, the filesystem might have other, non-encryption-related + * constraints that prevent DIO from actually being supported.) + */ +bool fscrypt_dio_supported(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 true; + + /* We only support DIO with inline crypto, not fs-layer crypto. */ + if (!fscrypt_inode_uses_inline_crypto(inode)) + return false; + + /* + * 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. + * + * We require that the user-provided memory buffers be filesystem 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 imply that data units 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 false; + + return true; +} +EXPORT_SYMBOL_GPL(fscrypt_dio_supported); + +/** + * 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 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; + u32 dun; + + if (!fscrypt_inode_uses_inline_crypto(inode)) + return nr_blocks; + + if (nr_blocks <= 1) + return nr_blocks; + + ci = inode->i_crypt_info; + 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); |