// SPDX-License-Identifier: GPL-2.0 /* * Utility functions for file contents encryption/decryption on * block device-based filesystems. * * Copyright (C) 2015, Google, Inc. * Copyright (C) 2015, Motorola Mobility */ #include <linux/pagemap.h> #include <linux/module.h> #include <linux/bio.h> #include <linux/namei.h> #include "fscrypt_private.h" /** * fscrypt_decrypt_bio() - decrypt the contents of a bio * @bio: the bio to decrypt * * Decrypt the contents of a "read" bio following successful completion of the * underlying disk read. The bio must be reading a whole number of blocks of an * encrypted file directly into the page cache. If the bio is reading the * ciphertext into bounce pages instead of the page cache (for example, because * the file is also compressed, so decompression is required after decryption), * then this function isn't applicable. This function may sleep, so it must be * called from a workqueue rather than from the bio's bi_end_io callback. * * This function sets PG_error on any pages that contain any blocks that failed * to be decrypted. The filesystem must not mark such pages uptodate. */ void fscrypt_decrypt_bio(struct bio *bio) { struct bio_vec *bv; struct bvec_iter_all iter_all; bio_for_each_segment_all(bv, bio, iter_all) { struct page *page = bv->bv_page; int ret = fscrypt_decrypt_pagecache_blocks(page, bv->bv_len, bv->bv_offset); if (ret) SetPageError(page); } } EXPORT_SYMBOL(fscrypt_decrypt_bio); static int fscrypt_zeroout_range_inline_crypt(const struct inode *inode, pgoff_t lblk, sector_t pblk, unsigned int len) { const unsigned int blockbits = inode->i_blkbits; const unsigned int blocks_per_page = 1 << (PAGE_SHIFT - blockbits); struct bio *bio; int ret, err = 0; int num_pages = 0; /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */ bio = bio_alloc(inode->i_sb->s_bdev, BIO_MAX_VECS, REQ_OP_WRITE, GFP_NOFS); while (len) { unsigned int blocks_this_page = min(len, blocks_per_page); unsigned int bytes_this_page = blocks_this_page << blockbits; if (num_pages == 0) { fscrypt_set_bio_crypt_ctx(bio, inode, lblk, GFP_NOFS); bio->bi_iter.bi_sector = pblk << (blockbits - SECTOR_SHIFT); } ret = bio_add_page(bio, ZERO_PAGE(0), bytes_this_page, 0); if (WARN_ON(ret != bytes_this_page)) { err = -EIO; goto out; } num_pages++; len -= blocks_this_page; lblk += blocks_this_page; pblk += blocks_this_page; if (num_pages == BIO_MAX_VECS || !len || !fscrypt_mergeable_bio(bio, inode, lblk)) { err = submit_bio_wait(bio); if (err) goto out; bio_reset(bio, inode->i_sb->s_bdev, REQ_OP_WRITE); num_pages = 0; } } out: bio_put(bio); return err; } /** * fscrypt_zeroout_range() - zero out a range of blocks in an encrypted file * @inode: the file's inode * @lblk: the first file logical block to zero out * @pblk: the first filesystem physical block to zero out * @len: number of blocks to zero out * * Zero out filesystem blocks in an encrypted regular file on-disk, i.e. write * ciphertext blocks which decrypt to the all-zeroes block. The blocks must be * both logically and physically contiguous. It's also assumed that the * filesystem only uses a single block device, ->s_bdev. * * Note that since each block uses a different IV, this involves writing a * different ciphertext to each block; we can't simply reuse the same one. * * Return: 0 on success; -errno on failure. */ int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk, sector_t pblk, unsigned int len) { const unsigned int blockbits = inode->i_blkbits; const unsigned int blocksize = 1 << blockbits; const unsigned int blocks_per_page_bits = PAGE_SHIFT - blockbits; const unsigned int blocks_per_page = 1 << blocks_per_page_bits; struct page *pages[16]; /* write up to 16 pages at a time */ unsigned int nr_pages; unsigned int i; unsigned int offset; struct bio *bio; int ret, err; if (len == 0) return 0; if (fscrypt_inode_uses_inline_crypto(inode)) return fscrypt_zeroout_range_inline_crypt(inode, lblk, pblk, len); BUILD_BUG_ON(ARRAY_SIZE(pages) > BIO_MAX_VECS); nr_pages = min_t(unsigned int, ARRAY_SIZE(pages), (len + blocks_per_page - 1) >> blocks_per_page_bits); /* * We need at least one page for ciphertext. Allocate the first one * from a mempool, with __GFP_DIRECT_RECLAIM set so that it can't fail. * * Any additional page allocations are allowed to fail, as they only * help performance, and waiting on the mempool for them could deadlock. */ for (i = 0; i < nr_pages; i++) { pages[i] = fscrypt_alloc_bounce_page(i == 0 ? GFP_NOFS : GFP_NOWAIT | __GFP_NOWARN); if (!pages[i]) break; } nr_pages = i; if (WARN_ON(nr_pages <= 0)) return -EINVAL; /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */ bio = bio_alloc(inode->i_sb->s_bdev, nr_pages, REQ_OP_WRITE, GFP_NOFS); do { bio->bi_iter.bi_sector = pblk << (blockbits - 9); i = 0; offset = 0; do { err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk, ZERO_PAGE(0), pages[i], blocksize, offset, GFP_NOFS); if (err) goto out; lblk++; pblk++; len--; offset += blocksize; if (offset == PAGE_SIZE || len == 0) { ret = bio_add_page(bio, pages[i++], offset, 0); if (WARN_ON(ret != offset)) { err = -EIO; goto out; } offset = 0; } } while (i != nr_pages && len != 0); err = submit_bio_wait(bio); if (err) goto out; bio_reset(bio, inode->i_sb->s_bdev, REQ_OP_WRITE); } while (len != 0); err = 0; out: bio_put(bio); for (i = 0; i < nr_pages; i++) fscrypt_free_bounce_page(pages[i]); return err; } EXPORT_SYMBOL(fscrypt_zeroout_range);