1 files changed, 193 insertions, 0 deletions
diff --git a/fs/crypto/bio.c b/fs/crypto/bio.c
new file mode 100644
index 0000000000..62e1a3dd83
--- /dev/null
+++ b/fs/crypto/bio.c
@@ -0,0 +1,193 @@
+// 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.
+ *
+ * Return: %true on success; %false on failure.  On failure, bio->bi_status is
+ *	   also set to an error status.
+ */
+bool fscrypt_decrypt_bio(struct bio *bio)
+{
+	struct folio_iter fi;
+
+	bio_for_each_folio_all(fi, bio) {
+		int err = fscrypt_decrypt_pagecache_blocks(fi.folio, fi.length,
+							   fi.offset);
+
+		if (err) {
+			bio->bi_status = errno_to_blk_status(err);
+			return false;
+		}
+	}
+	return true;
+}
+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_ONCE(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_ONCE(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_ONCE(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);