linux/fs/ext4/crypto.c

// SPDX-License-Identifier: GPL-2.0

#include <linux/quotaops.h>

#include "ext4.h"
#include "xattr.h"
#include "ext4_jbd2.h"

static int ext4_get_context(struct inode *inode, void *ctx, size_t len)
{
	return ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
				 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, ctx, len);
}

static int ext4_set_context(struct inode *inode, const void *ctx, size_t len,
							void *fs_data)
{
	handle_t *handle = fs_data;
	int res, res2, credits, retries = 0;

	/*
	 * Encrypting the root directory is not allowed because e2fsck expects
	 * lost+found to exist and be unencrypted, and encrypting the root
	 * directory would imply encrypting the lost+found directory as well as
	 * the filename "lost+found" itself.
	 */
	if (inode->i_ino == EXT4_ROOT_INO)
		return -EPERM;

	if (WARN_ON_ONCE(IS_DAX(inode) && i_size_read(inode)))
		return -EINVAL;

	if (ext4_test_inode_flag(inode, EXT4_INODE_DAX))
		return -EOPNOTSUPP;

	res = ext4_convert_inline_data(inode);
	if (res)
		return res;

	/*
	 * If a journal handle was specified, then the encryption context is
	 * being set on a new inode via inheritance and is part of a larger
	 * transaction to create the inode.  Otherwise the encryption context is
	 * being set on an existing inode in its own transaction.  Only in the
	 * latter case should the "retry on ENOSPC" logic be used.
	 */

	if (handle) {
		res = ext4_xattr_set_handle(handle, inode,
					    EXT4_XATTR_INDEX_ENCRYPTION,
					    EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
					    ctx, len, 0);
		if (!res) {
			ext4_set_inode_flag(inode, EXT4_INODE_ENCRYPT);
			ext4_clear_inode_state(inode,
					EXT4_STATE_MAY_INLINE_DATA);
			/*
			 * Update inode->i_flags - S_ENCRYPTED will be enabled,
			 * S_DAX may be disabled
			 */
			ext4_set_inode_flags(inode, false);
		}
		return res;
	}

	res = dquot_initialize(inode);
	if (res)
		return res;
retry:
	res = ext4_xattr_set_credits(inode, len, false /* is_create */,
				     &credits);
	if (res)
		return res;

	handle = ext4_journal_start(inode, EXT4_HT_MISC, credits);
	if (IS_ERR(handle))
		return PTR_ERR(handle);

	res = ext4_xattr_set_handle(handle, inode, EXT4_XATTR_INDEX_ENCRYPTION,
				    EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
				    ctx, len, 0);
	if (!res) {
		ext4_set_inode_flag(inode, EXT4_INODE_ENCRYPT);
		/*
		 * Update inode->i_flags - S_ENCRYPTED will be enabled,
		 * S_DAX may be disabled
		 */
		ext4_set_inode_flags(inode, false);
		res = ext4_mark_inode_dirty(handle, inode);
		if (res)
			EXT4_ERROR_INODE(inode, "Failed to mark inode dirty");
	}
	res2 = ext4_journal_stop(handle);

	if (res == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
		goto retry;
	if (!res)
		res = res2;
	return res;
}

static const union fscrypt_policy *ext4_get_dummy_policy(struct super_block *sb)
{
	return EXT4_SB(sb)->s_dummy_enc_policy.policy;
}

static bool ext4_has_stable_inodes(struct super_block *sb)
{
	return ext4_has_feature_stable_inodes(sb);
}

static void ext4_get_ino_and_lblk_bits(struct super_block *sb,
				       int *ino_bits_ret, int *lblk_bits_ret)
{
	*ino_bits_ret = 8 * sizeof(EXT4_SB(sb)->s_es->s_inodes_count);
	*lblk_bits_ret = 8 * sizeof(ext4_lblk_t);
}

const struct fscrypt_operations ext4_cryptops = {
	.key_prefix		= "ext4:",
	.get_context		= ext4_get_context,
	.set_context		= ext4_set_context,
	.get_dummy_policy	= ext4_get_dummy_policy,
	.empty_dir		= ext4_empty_dir,
	.has_stable_inodes	= ext4_has_stable_inodes,
	.get_ino_and_lblk_bits	= ext4_get_ino_and_lblk_bits,
};