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

Satya Tangirala
2019-12-19T00:32:06Z

I messed up while using git and managed to overwrite the author field in
the patch - it should read "Eric Biggers <ebiggers@google.com>" instead.
I'll fix that in the next patch version, sorry.

On Wed, Dec 18, 2019 at 04:12:41PM -0800, Eric Biggers wrote:

> [+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?
>
Ok, I will.
> > ---
> > 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.
>
Will fix in the next version.
> > 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?
>
Right, I'll add this change to the next version too.
> - Eric