1 files changed, 216 insertions, 0 deletions
diff --git a/fs/crypto/bio.c b/fs/crypto/bio.c
new file mode 100644
index 000000000..d07740680
--- /dev/null
+++ b/fs/crypto/bio.c
@@ -0,0 +1,216 @@
+// 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/bio.h>
+#include <linux/export.h>
+#include <linux/module.h>
+#include <linux/namei.h>
+#include <linux/pagemap.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);
+
+struct fscrypt_zero_done {
+	atomic_t		pending;
+	blk_status_t		status;
+	struct completion	done;
+};
+
+static void fscrypt_zeroout_range_done(struct fscrypt_zero_done *done)
+{
+	if (atomic_dec_and_test(&done->pending))
+		complete(&done->done);
+}
+
+static void fscrypt_zeroout_range_end_io(struct bio *bio)
+{
+	struct fscrypt_zero_done *done = bio->bi_private;
+
+	if (bio->bi_status)
+		cmpxchg(&done->status, 0, bio->bi_status);
+	fscrypt_zeroout_range_done(done);
+	bio_put(bio);
+}
+
+static int fscrypt_zeroout_range_inline_crypt(const struct inode *inode,
+					      loff_t pos, sector_t sector,
+					      u64 len)
+{
+	struct fscrypt_zero_done done = {
+		.pending	= ATOMIC_INIT(1),
+		.done		= COMPLETION_INITIALIZER_ONSTACK(done.done),
+	};
+
+	while (len) {
+		struct bio *bio;
+		unsigned int n;
+
+		bio = bio_alloc(inode->i_sb->s_bdev, BIO_MAX_VECS, REQ_OP_WRITE,
+				GFP_NOFS);
+		bio->bi_iter.bi_sector = sector;
+		bio->bi_private = &done;
+		bio->bi_end_io = fscrypt_zeroout_range_end_io;
+		fscrypt_set_bio_crypt_ctx(bio, inode, pos, GFP_NOFS);
+
+		for (n = 0; n < BIO_MAX_VECS; n++) {
+			unsigned int bytes_this_page = min(len, PAGE_SIZE);
+
+			__bio_add_page(bio, ZERO_PAGE(0), bytes_this_page, 0);
+			len -= bytes_this_page;
+			pos += bytes_this_page;
+			sector += (bytes_this_page >> SECTOR_SHIFT);
+			if (!len || !fscrypt_mergeable_bio(bio, inode, pos))
+				break;
+		}
+
+		atomic_inc(&done.pending);
+		blk_crypto_submit_bio(bio);
+	}
+
+	fscrypt_zeroout_range_done(&done);
+
+	wait_for_completion(&done.done);
+	return blk_status_to_errno(done.status);
+}
+
+/**
+ * fscrypt_zeroout_range() - zero out a range of blocks in an encrypted file
+ * @inode: the file's inode
+ * @pos: the first file position (in bytes) to zero out
+ * @sector: the first sector to zero out
+ * @len: bytes 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.  @len must be a
+ * multiple of the file system logical block size.
+ *
+ * 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, loff_t pos,
+			  sector_t sector, u64 len)
+{
+	const struct fscrypt_inode_info *ci = fscrypt_get_inode_info_raw(inode);
+	const unsigned int du_bits = ci->ci_data_unit_bits;
+	const unsigned int du_size = 1U << du_bits;
+	const unsigned int du_per_page_bits = PAGE_SHIFT - du_bits;
+	const unsigned int du_per_page = 1U << du_per_page_bits;
+	u64 du_index = pos >> du_bits;
+	u64 du_remaining = len >> du_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, pos, sector,
+							  len);
+
+	BUILD_BUG_ON(ARRAY_SIZE(pages) > BIO_MAX_VECS);
+	nr_pages = min_t(u64, ARRAY_SIZE(pages),
+			 (du_remaining + du_per_page - 1) >> du_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);
+		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 = sector;
+
+		i = 0;
+		offset = 0;
+		do {
+			err = fscrypt_crypt_data_unit(ci, FS_ENCRYPT, du_index,
+						      ZERO_PAGE(0), pages[i],
+						      du_size, offset);
+			if (err)
+				goto out;
+			du_index++;
+			sector += 1U << (du_bits - SECTOR_SHIFT);
+			du_remaining--;
+			offset += du_size;
+			if (offset == PAGE_SIZE || du_remaining == 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 && du_remaining != 0);
+
+		err = submit_bio_wait(bio);
+		if (err)
+			goto out;
+		bio_reset(bio, inode->i_sb->s_bdev, REQ_OP_WRITE);
+	} while (du_remaining != 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);