fscrypt only uses SHA-256 for AES-128-CBC-ESSIV, which isn't the default
and is only recommended on platforms that have hardware accelerated
AES-CBC but not AES-XTS.  There's no link-time dependency, since SHA-256
is requested via the crypto API on first use.

To reduce bloat, we should limit FS_ENCRYPTION to selecting the default
algorithms only.  SHA-256 by itself isn't that much bloat, but it's
being discussed to move ESSIV into a crypto API template, which would
incidentally bring in other things like "authenc" support, which would
all end up being built-in since FS_ENCRYPTION is now a bool.

For Adiantum encryption we already just document that users who want to
use it have to enable CONFIG_CRYPTO_ADIANTUM themselves.  So, let's do
the same for AES-128-CBC-ESSIV and CONFIG_CRYPTO_SHA256.

Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Eric Biggers <ebiggers@google.com>

These should have been removed during commit 544d08fde258 ("fscrypt: use
a common logging function"), but I missed them.

Signed-off-by: Eric Biggers <ebiggers@google.com>

The directory may have been removed when entering
fscrypt_ioctl_set_policy().  If so, the empty_dir() check will return
error for ext4 file system.

ext4_rmdir() sets i_size = 0, then ext4_empty_dir() reports an error
because 'inode->i_size < EXT4_DIR_REC_LEN(1) + EXT4_DIR_REC_LEN(2)'.  If
the fs is mounted with errors=panic, it will trigger a panic issue.

Add the check IS_DEADDIR() to fix this problem.

Fixes: 9bd8212f981e ("ext4 crypto: add encryption policy and password salt support")
Cc: <stable@vger.kernel.org> # v4.1+
Signed-off-by: Hongjie Fang <hongjiefang@asrmicro.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>

In __fscrypt_decrypt_bio(), only decrypt the blocks that actually
comprise the bio, rather than assuming blocksize == PAGE_SIZE and
decrypting the entirety of every page used in the bio.

This is in preparation for allowing encryption on ext4 filesystems with
blocksize != PAGE_SIZE.

This is based on work by Chandan Rajendra.

Reviewed-by: Chandan Rajendra <chandan@linux.ibm.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>

Rename fscrypt_decrypt_page() to fscrypt_decrypt_pagecache_blocks() and
redefine its behavior to decrypt all filesystem blocks in the given
region of the given page, rather than assuming that the region consists
of just one filesystem block.  Also remove the 'inode' and 'lblk_num'
parameters, since they can be retrieved from the page as it's already
assumed to be a pagecache page.

This is in preparation for allowing encryption on ext4 filesystems with
blocksize != PAGE_SIZE.

This is based on work by Chandan Rajendra.

Reviewed-by: Chandan Rajendra <chandan@linux.ibm.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>

Currently fscrypt_decrypt_page() does one of two logically distinct
things depending on whether FS_CFLG_OWN_PAGES is set in the filesystem's
fscrypt_operations: decrypt a pagecache page in-place, or decrypt a
filesystem block in-place in any page.  Currently these happen to share
the same implementation, but this conflates the notion of blocks and
pages.  It also makes it so that all callers have to provide inode and
lblk_num, when fscrypt could determine these itself for pagecache pages.

Therefore, move the FS_CFLG_OWN_PAGES behavior into a new function
fscrypt_decrypt_block_inplace().  This mirrors
fscrypt_encrypt_block_inplace().

This is in preparation for allowing encryption on ext4 filesystems with
blocksize != PAGE_SIZE.

Reviewed-by: Chandan Rajendra <chandan@linux.ibm.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>

Adjust fscrypt_zeroout_range() to encrypt a block at a time rather than
a page at a time, so that it works when blocksize < PAGE_SIZE.

This isn't optimized for performance, but then again this function
already wasn't optimized for performance.  As a future optimization, we
could submit much larger bios here.

This is in preparation for allowing encryption on ext4 filesystems with
blocksize != PAGE_SIZE.

This is based on work by Chandan Rajendra.

Reviewed-by: Chandan Rajendra <chandan@linux.ibm.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>

Rename fscrypt_encrypt_page() to fscrypt_encrypt_pagecache_blocks() and
redefine its behavior to encrypt all filesystem blocks from the given
region of the given page, rather than assuming that the region consists
of just one filesystem block.  Also remove the 'inode' and 'lblk_num'
parameters, since they can be retrieved from the page as it's already
assumed to be a pagecache page.

This is in preparation for allowing encryption on ext4 filesystems with
blocksize != PAGE_SIZE.

This is based on work by Chandan Rajendra.

Reviewed-by: Chandan Rajendra <chandan@linux.ibm.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>

fscrypt_encrypt_page() behaves very differently depending on whether the
filesystem set FS_CFLG_OWN_PAGES in its fscrypt_operations.  This makes
the function difficult to understand and document.  It also makes it so
that all callers have to provide inode and lblk_num, when fscrypt could
determine these itself for pagecache pages.

Therefore, move the FS_CFLG_OWN_PAGES behavior into a new function
fscrypt_encrypt_block_inplace().

This is in preparation for allowing encryption on ext4 filesystems with
blocksize != PAGE_SIZE.

Reviewed-by: Chandan Rajendra <chandan@linux.ibm.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>

Replace some BUG_ON()s with WARN_ON_ONCE() and returning an error code,
and move the check for len divisible by FS_CRYPTO_BLOCK_SIZE into
fscrypt_crypt_block() so that it's done for both encryption and
decryption, not just encryption.

Reviewed-by: Chandan Rajendra <chandan@linux.ibm.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>