Re: [PATCH v6 9/9] ext4: add inline encryption support

Eric Biggers
2019-12-19T00:12:45Z

[+Cc linux-ext4]

On Wed, Dec 18, 2019 at 06:51:36AM -0800, Satya Tangirala wrote:
> Wire up ext4 to support inline encryption via the helper functions which
> fs/crypto/ now provides. This includes:
>
> - Adding a mount option 'inlinecrypt' which enables inline encryption
> on encrypted files where it can be used.
>
> - Setting the bio_crypt_ctx on bios that will be submitted to an
> inline-encrypted file.
>
> Note: submit_bh_wbc() in fs/buffer.c also needed to be patched for
> this part, since ext4 sometimes uses ll_rw_block() on file data.
>
> - Not adding logically discontiguous data to bios that will be submitted
> to an inline-encrypted file.
>
> - Not doing filesystem-layer crypto on inline-encrypted files.
>
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> Signed-off-by: Satya Tangirala <satyat@google.com>

In the next version can you please add linux-ext4 to Cc for the series?

> ---
> fs/buffer.c | 2 ++
> fs/ext4/ext4.h | 1 +
> fs/ext4/inode.c | 4 ++--
> fs/ext4/page-io.c | 6 ++++--
> fs/ext4/readpage.c | 11 ++++++++---
> fs/ext4/super.c | 13 +++++++++++++
> 6 files changed, 30 insertions(+), 7 deletions(-)
>
> diff --git a/fs/buffer.c b/fs/buffer.c
> index d8c7242426bb..3ad000db4a19 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -3108,6 +3108,8 @@ static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh,
> */
> bio = bio_alloc(GFP_NOIO, 1);
>
> + fscrypt_set_bio_crypt_ctx_bh(bio, bh, GFP_NOIO);
> +
> bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
> bio_set_dev(bio, bh->b_bdev);
> bio->bi_write_hint = write_hint;

In 5.5, there was some decryption code added to fs/buffer.c in order to support
ext4 encryption with blocksize < PAGE_SIZE:

static void end_buffer_async_read_io(struct buffer_head *bh, int uptodate)
{
/* Decrypt if needed */
if (uptodate && IS_ENABLED(CONFIG_FS_ENCRYPTION) &&
IS_ENCRYPTED(bh->b_page->mapping->host) &&
S_ISREG(bh->b_page->mapping->host->i_mode)) {
...

This needs to be updated to use fscrypt_inode_uses_fs_layer_crypto() instead, so
that the filesystem-layer decryption is not done when the file is already using
inline decryption.

> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index f8578caba40d..aeaa01724d7c 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -1153,6 +1153,7 @@ struct ext4_inode_info {
> #define EXT4_MOUNT_JOURNAL_CHECKSUM 0x800000 /* Journal checksums */
> #define EXT4_MOUNT_JOURNAL_ASYNC_COMMIT 0x1000000 /* Journal Async Commit */
> #define EXT4_MOUNT_WARN_ON_ERROR 0x2000000 /* Trigger WARN_ON on error */
> +#define EXT4_MOUNT_INLINECRYPT 0x4000000 /* Inline encryption support */
> #define EXT4_MOUNT_DELALLOC 0x8000000 /* Delalloc support */
> #define EXT4_MOUNT_DATA_ERR_ABORT 0x10000000 /* Abort on file data write */
> #define EXT4_MOUNT_BLOCK_VALIDITY 0x20000000 /* Block validity checking */
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 28f28de0c1b6..44d9651b8638 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -1090,7 +1090,7 @@ static int ext4_block_write_begin(struct page *page, loff_t pos, unsigned len,
> }
> if (unlikely(err)) {
> page_zero_new_buffers(page, from, to);
> - } else if (IS_ENCRYPTED(inode) && S_ISREG(inode->i_mode)) {
> + } else if (fscrypt_inode_uses_fs_layer_crypto(inode)) {
> for (i = 0; i < nr_wait; i++) {
> int err2;
>
> @@ -3698,7 +3698,7 @@ static int __ext4_block_zero_page_range(handle_t *handle,
> /* Uhhuh. Read error. Complain and punt. */
> if (!buffer_uptodate(bh))
> goto unlock;
> - if (S_ISREG(inode->i_mode) && IS_ENCRYPTED(inode)) {
> + if (fscrypt_inode_uses_fs_layer_crypto(inode)) {
> /* We expect the key to be set. */
> BUG_ON(!fscrypt_has_encryption_key(inode));
> WARN_ON_ONCE(fscrypt_decrypt_pagecache_blocks(
> diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
> index 24aeedb8fc75..acde754cc5ca 100644
> --- a/fs/ext4/page-io.c
> +++ b/fs/ext4/page-io.c
> @@ -404,6 +404,7 @@ static void io_submit_init_bio(struct ext4_io_submit *io,
> * __GFP_DIRECT_RECLAIM is set, see comments for bio_alloc_bioset().
> */
> bio = bio_alloc(GFP_NOIO, BIO_MAX_PAGES);
> + fscrypt_set_bio_crypt_ctx_bh(bio, bh, GFP_NOIO);
> bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
> bio_set_dev(bio, bh->b_bdev);
> bio->bi_end_io = ext4_end_bio;
> @@ -420,7 +421,8 @@ static void io_submit_add_bh(struct ext4_io_submit *io,
> {
> int ret;
>
> - if (io->io_bio && bh->b_blocknr != io->io_next_block) {
> + if (io->io_bio && (bh->b_blocknr != io->io_next_block ||
> + !fscrypt_mergeable_bio_bh(io->io_bio, bh))) {
> submit_and_retry:
> ext4_io_submit(io);
> }
> @@ -508,7 +510,7 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
> * (e.g. holes) to be unnecessarily encrypted, but this is rare and
> * can't happen in the common case of blocksize == PAGE_SIZE.
> */
> - if (IS_ENCRYPTED(inode) && S_ISREG(inode->i_mode) && nr_to_submit) {
> + if (fscrypt_inode_uses_fs_layer_crypto(inode) && nr_to_submit) {
> gfp_t gfp_flags = GFP_NOFS;
> unsigned int enc_bytes = round_up(len, i_blocksize(inode));
>
> diff --git a/fs/ext4/readpage.c b/fs/ext4/readpage.c
> index fef7755300c3..7844e27518b4 100644
> --- a/fs/ext4/readpage.c
> +++ b/fs/ext4/readpage.c
> @@ -183,7 +183,7 @@ static struct bio_post_read_ctx *get_bio_post_read_ctx(struct inode *inode,
> unsigned int post_read_steps = 0;
> struct bio_post_read_ctx *ctx = NULL;
>
> - if (IS_ENCRYPTED(inode) && S_ISREG(inode->i_mode))
> + if (fscrypt_inode_uses_fs_layer_crypto(inode))
> post_read_steps |= 1 << STEP_DECRYPT;
>
> if (ext4_need_verity(inode, first_idx))
> @@ -220,6 +220,7 @@ int ext4_mpage_readpages(struct address_space *mapping,
> const unsigned blkbits = inode->i_blkbits;
> const unsigned blocks_per_page = PAGE_SIZE >> blkbits;
> const unsigned blocksize = 1 << blkbits;
> + sector_t next_block;
> sector_t block_in_file;
> sector_t last_block;
> sector_t last_block_in_file;
> @@ -252,7 +253,8 @@ int ext4_mpage_readpages(struct address_space *mapping,
> if (page_has_buffers(page))
> goto confused;
>
> - block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);
> + block_in_file = next_block =
> + (sector_t)page->index << (PAGE_SHIFT - blkbits);
> last_block = block_in_file + nr_pages * blocks_per_page;
> last_block_in_file = (ext4_readpage_limit(inode) +
> blocksize - 1) >> blkbits;
> @@ -352,7 +354,8 @@ int ext4_mpage_readpages(struct address_space *mapping,
> * This page will go to BIO. Do we need to send this
> * BIO off first?
> */
> - if (bio && (last_block_in_bio != blocks[0] - 1)) {
> + if (bio && (last_block_in_bio != blocks[0] - 1 ||
> + !fscrypt_mergeable_bio(bio, inode, next_block))) {
> submit_and_realloc:
> submit_bio(bio);
> bio = NULL;
> @@ -366,6 +369,8 @@ int ext4_mpage_readpages(struct address_space *mapping,
> */
> bio = bio_alloc(GFP_KERNEL,
> min_t(int, nr_pages, BIO_MAX_PAGES));
> + fscrypt_set_bio_crypt_ctx(bio, inode, next_block,
> + GFP_KERNEL);
> ctx = get_bio_post_read_ctx(inode, bio, page->index);
> if (IS_ERR(ctx)) {
> bio_put(bio);
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 1d82b56d9b11..0a6b60620942 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -1357,6 +1357,11 @@ static void ext4_get_ino_and_lblk_bits(struct super_block *sb,
> *lblk_bits_ret = 8 * sizeof(ext4_lblk_t);
> }
>
> +static bool ext4_inline_crypt_enabled(struct super_block *sb)
> +{
> + return test_opt(sb, INLINECRYPT);
> +}
> +
> static const struct fscrypt_operations ext4_cryptops = {
> .key_prefix = "ext4:",
> .get_context = ext4_get_context,
> @@ -1366,6 +1371,7 @@ static const struct fscrypt_operations ext4_cryptops = {
> .max_namelen = EXT4_NAME_LEN,
> .has_stable_inodes = ext4_has_stable_inodes,
> .get_ino_and_lblk_bits = ext4_get_ino_and_lblk_bits,
> + .inline_crypt_enabled = ext4_inline_crypt_enabled,
> };
> #endif
>
> @@ -1460,6 +1466,7 @@ enum {
> Opt_journal_path, Opt_journal_checksum, Opt_journal_async_commit,
> Opt_abort, Opt_data_journal, Opt_data_ordered, Opt_data_writeback,
> Opt_data_err_abort, Opt_data_err_ignore, Opt_test_dummy_encryption,
> + Opt_inlinecrypt,
> Opt_usrjquota, Opt_grpjquota, Opt_offusrjquota, Opt_offgrpjquota,
> Opt_jqfmt_vfsold, Opt_jqfmt_vfsv0, Opt_jqfmt_vfsv1, Opt_quota,
> Opt_noquota, Opt_barrier, Opt_nobarrier, Opt_err,
> @@ -1556,6 +1563,7 @@ static const match_table_t tokens = {
> {Opt_noinit_itable, "noinit_itable"},
> {Opt_max_dir_size_kb, "max_dir_size_kb=%u"},
> {Opt_test_dummy_encryption, "test_dummy_encryption"},
> + {Opt_inlinecrypt, "inlinecrypt"},
> {Opt_nombcache, "nombcache"},
> {Opt_nombcache, "no_mbcache"}, /* for backward compatibility */
> {Opt_removed, "check=none"}, /* mount option from ext2/3 */
> @@ -1767,6 +1775,11 @@ static const struct mount_opts {
> {Opt_jqfmt_vfsv1, QFMT_VFS_V1, MOPT_QFMT},
> {Opt_max_dir_size_kb, 0, MOPT_GTE0},
> {Opt_test_dummy_encryption, 0, MOPT_GTE0},
> +#ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
> + {Opt_inlinecrypt, EXT4_MOUNT_INLINECRYPT, MOPT_SET},
> +#else
> + {Opt_inlinecrypt, EXT4_MOUNT_INLINECRYPT, MOPT_NOSUPPORT},
> +#endif
> {Opt_nombcache, EXT4_MOUNT_NO_MBCACHE, MOPT_SET},
> {Opt_err, 0, 0}
> };

On v5 there was a discussion about using a flag like SB_INLINECRYPT to replace
the ->inline_crypt_enabled() function. Was this considered?

- Eric