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Diffstat (limited to 'include/linux/fscrypt.h')
| -rw-r--r-- | include/linux/fscrypt.h | 783 |
1 files changed, 783 insertions, 0 deletions
diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h new file mode 100644 index 000000000000..2aad2f949b9e --- /dev/null +++ b/include/linux/fscrypt.h @@ -0,0 +1,783 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * fscrypt.h: declarations for per-file encryption + * + * Filesystems that implement per-file encryption must include this header + * file. + * + * Copyright (C) 2015, Google, Inc. + * + * Written by Michael Halcrow, 2015. + * Modified by Jaegeuk Kim, 2015. + */ +#ifndef _LINUX_FSCRYPT_H +#define _LINUX_FSCRYPT_H + +#include <linux/fs.h> +#include <linux/mm.h> +#include <linux/slab.h> +#include <uapi/linux/fscrypt.h> + +#define FS_CRYPTO_BLOCK_SIZE 16 + +struct fscrypt_ctx; +struct fscrypt_info; + +struct fscrypt_str { + unsigned char *name; + u32 len; +}; + +struct fscrypt_name { + const struct qstr *usr_fname; + struct fscrypt_str disk_name; + u32 hash; + u32 minor_hash; + struct fscrypt_str crypto_buf; + bool is_ciphertext_name; +}; + +#define FSTR_INIT(n, l) { .name = n, .len = l } +#define FSTR_TO_QSTR(f) QSTR_INIT((f)->name, (f)->len) +#define fname_name(p) ((p)->disk_name.name) +#define fname_len(p) ((p)->disk_name.len) + +/* Maximum value for the third parameter of fscrypt_operations.set_context(). */ +#define FSCRYPT_SET_CONTEXT_MAX_SIZE 40 + +#ifdef CONFIG_FS_ENCRYPTION +/* + * fscrypt superblock flags + */ +#define FS_CFLG_OWN_PAGES (1U << 1) + +/* + * crypto operations for filesystems + */ +struct fscrypt_operations { + unsigned int flags; + const char *key_prefix; + int (*get_context)(struct inode *, void *, size_t); + int (*set_context)(struct inode *, const void *, size_t, void *); + bool (*dummy_context)(struct inode *); + bool (*empty_dir)(struct inode *); + unsigned int max_namelen; +}; + +/* Decryption work */ +struct fscrypt_ctx { + union { + struct { + struct bio *bio; + struct work_struct work; + }; + struct list_head free_list; /* Free list */ + }; + u8 flags; /* Flags */ +}; + +static inline bool fscrypt_has_encryption_key(const struct inode *inode) +{ + /* pairs with cmpxchg_release() in fscrypt_get_encryption_info() */ + return READ_ONCE(inode->i_crypt_info) != NULL; +} + +static inline bool fscrypt_dummy_context_enabled(struct inode *inode) +{ + return inode->i_sb->s_cop->dummy_context && + inode->i_sb->s_cop->dummy_context(inode); +} + +/* + * When d_splice_alias() moves a directory's encrypted alias to its decrypted + * alias as a result of the encryption key being added, DCACHE_ENCRYPTED_NAME + * must be cleared. Note that we don't have to support arbitrary moves of this + * flag because fscrypt doesn't allow encrypted aliases to be the source or + * target of a rename(). + */ +static inline void fscrypt_handle_d_move(struct dentry *dentry) +{ + dentry->d_flags &= ~DCACHE_ENCRYPTED_NAME; +} + +/* crypto.c */ +extern void fscrypt_enqueue_decrypt_work(struct work_struct *); +extern struct fscrypt_ctx *fscrypt_get_ctx(gfp_t); +extern void fscrypt_release_ctx(struct fscrypt_ctx *); + +extern struct page *fscrypt_encrypt_pagecache_blocks(struct page *page, + unsigned int len, + unsigned int offs, + gfp_t gfp_flags); +extern int fscrypt_encrypt_block_inplace(const struct inode *inode, + struct page *page, unsigned int len, + unsigned int offs, u64 lblk_num, + gfp_t gfp_flags); + +extern int fscrypt_decrypt_pagecache_blocks(struct page *page, unsigned int len, + unsigned int offs); +extern int fscrypt_decrypt_block_inplace(const struct inode *inode, + struct page *page, unsigned int len, + unsigned int offs, u64 lblk_num); + +static inline bool fscrypt_is_bounce_page(struct page *page) +{ + return page->mapping == NULL; +} + +static inline struct page *fscrypt_pagecache_page(struct page *bounce_page) +{ + return (struct page *)page_private(bounce_page); +} + +extern void fscrypt_free_bounce_page(struct page *bounce_page); + +/* policy.c */ +extern int fscrypt_ioctl_set_policy(struct file *, const void __user *); +extern int fscrypt_ioctl_get_policy(struct file *, void __user *); +extern int fscrypt_ioctl_get_policy_ex(struct file *, void __user *); +extern int fscrypt_has_permitted_context(struct inode *, struct inode *); +extern int fscrypt_inherit_context(struct inode *, struct inode *, + void *, bool); +/* keyring.c */ +extern void fscrypt_sb_free(struct super_block *sb); +extern int fscrypt_ioctl_add_key(struct file *filp, void __user *arg); +extern int fscrypt_ioctl_remove_key(struct file *filp, void __user *arg); +extern int fscrypt_ioctl_remove_key_all_users(struct file *filp, + void __user *arg); +extern int fscrypt_ioctl_get_key_status(struct file *filp, void __user *arg); +extern int fscrypt_register_key_removal_notifier(struct notifier_block *nb); +extern int fscrypt_unregister_key_removal_notifier(struct notifier_block *nb); + +/* keysetup.c */ +extern int fscrypt_get_encryption_info(struct inode *); +extern void fscrypt_put_encryption_info(struct inode *); +extern void fscrypt_free_inode(struct inode *); +extern int fscrypt_drop_inode(struct inode *inode); + +/* fname.c */ +extern int fscrypt_setup_filename(struct inode *, const struct qstr *, + int lookup, struct fscrypt_name *); + +static inline void fscrypt_free_filename(struct fscrypt_name *fname) +{ + kfree(fname->crypto_buf.name); +} + +extern int fscrypt_fname_alloc_buffer(const struct inode *, u32, + struct fscrypt_str *); +extern void fscrypt_fname_free_buffer(struct fscrypt_str *); +extern int fscrypt_fname_disk_to_usr(struct inode *, u32, u32, + const struct fscrypt_str *, struct fscrypt_str *); + +#define FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE 32 + +/* Extracts the second-to-last ciphertext block; see explanation below */ +#define FSCRYPT_FNAME_DIGEST(name, len) \ + ((name) + round_down((len) - FS_CRYPTO_BLOCK_SIZE - 1, \ + FS_CRYPTO_BLOCK_SIZE)) + +#define FSCRYPT_FNAME_DIGEST_SIZE FS_CRYPTO_BLOCK_SIZE + +/** + * fscrypt_digested_name - alternate identifier for an on-disk filename + * + * When userspace lists an encrypted directory without access to the key, + * filenames whose ciphertext is longer than FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE + * bytes are shown in this abbreviated form (base64-encoded) rather than as the + * full ciphertext (base64-encoded). This is necessary to allow supporting + * filenames up to NAME_MAX bytes, since base64 encoding expands the length. + * + * To make it possible for filesystems to still find the correct directory entry + * despite not knowing the full on-disk name, we encode any filesystem-specific + * 'hash' and/or 'minor_hash' which the filesystem may need for its lookups, + * followed by the second-to-last ciphertext block of the filename. Due to the + * use of the CBC-CTS encryption mode, the second-to-last ciphertext block + * depends on the full plaintext. (Note that ciphertext stealing causes the + * last two blocks to appear "flipped".) This makes accidental collisions very + * unlikely: just a 1 in 2^128 chance for two filenames to collide even if they + * share the same filesystem-specific hashes. + * + * However, this scheme isn't immune to intentional collisions, which can be + * created by anyone able to create arbitrary plaintext filenames and view them + * without the key. Making the "digest" be a real cryptographic hash like + * SHA-256 over the full ciphertext would prevent this, although it would be + * less efficient and harder to implement, especially since the filesystem would + * need to calculate it for each directory entry examined during a search. + */ +struct fscrypt_digested_name { + u32 hash; + u32 minor_hash; + u8 digest[FSCRYPT_FNAME_DIGEST_SIZE]; +}; + +/** + * fscrypt_match_name() - test whether the given name matches a directory entry + * @fname: the name being searched for + * @de_name: the name from the directory entry + * @de_name_len: the length of @de_name in bytes + * + * Normally @fname->disk_name will be set, and in that case we simply compare + * that to the name stored in the directory entry. The only exception is that + * if we don't have the key for an encrypted directory and a filename in it is + * very long, then we won't have the full disk_name and we'll instead need to + * match against the fscrypt_digested_name. + * + * Return: %true if the name matches, otherwise %false. + */ +static inline bool fscrypt_match_name(const struct fscrypt_name *fname, + const u8 *de_name, u32 de_name_len) +{ + if (unlikely(!fname->disk_name.name)) { + const struct fscrypt_digested_name *n = + (const void *)fname->crypto_buf.name; + if (WARN_ON_ONCE(fname->usr_fname->name[0] != '_')) + return false; + if (de_name_len <= FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE) + return false; + return !memcmp(FSCRYPT_FNAME_DIGEST(de_name, de_name_len), + n->digest, FSCRYPT_FNAME_DIGEST_SIZE); + } + + if (de_name_len != fname->disk_name.len) + return false; + return !memcmp(de_name, fname->disk_name.name, fname->disk_name.len); +} + +/* bio.c */ +extern void fscrypt_decrypt_bio(struct bio *); +extern void fscrypt_enqueue_decrypt_bio(struct fscrypt_ctx *ctx, + struct bio *bio); +extern int fscrypt_zeroout_range(const struct inode *, pgoff_t, sector_t, + unsigned int); + +/* hooks.c */ +extern int fscrypt_file_open(struct inode *inode, struct file *filp); +extern int __fscrypt_prepare_link(struct inode *inode, struct inode *dir, + struct dentry *dentry); +extern int __fscrypt_prepare_rename(struct inode *old_dir, + struct dentry *old_dentry, + struct inode *new_dir, + struct dentry *new_dentry, + unsigned int flags); +extern int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry, + struct fscrypt_name *fname); +extern int __fscrypt_prepare_symlink(struct inode *dir, unsigned int len, + unsigned int max_len, + struct fscrypt_str *disk_link); +extern int __fscrypt_encrypt_symlink(struct inode *inode, const char *target, + unsigned int len, + struct fscrypt_str *disk_link); +extern const char *fscrypt_get_symlink(struct inode *inode, const void *caddr, + unsigned int max_size, + struct delayed_call *done); +#else /* !CONFIG_FS_ENCRYPTION */ + +static inline bool fscrypt_has_encryption_key(const struct inode *inode) +{ + return false; +} + +static inline bool fscrypt_dummy_context_enabled(struct inode *inode) +{ + return false; +} + +static inline void fscrypt_handle_d_move(struct dentry *dentry) +{ +} + +/* crypto.c */ +static inline void fscrypt_enqueue_decrypt_work(struct work_struct *work) +{ +} + +static inline struct fscrypt_ctx *fscrypt_get_ctx(gfp_t gfp_flags) +{ + return ERR_PTR(-EOPNOTSUPP); +} + +static inline void fscrypt_release_ctx(struct fscrypt_ctx *ctx) +{ + return; +} + +static inline struct page *fscrypt_encrypt_pagecache_blocks(struct page *page, + unsigned int len, + unsigned int offs, + gfp_t gfp_flags) +{ + return ERR_PTR(-EOPNOTSUPP); +} + +static inline int fscrypt_encrypt_block_inplace(const struct inode *inode, + struct page *page, + unsigned int len, + unsigned int offs, u64 lblk_num, + gfp_t gfp_flags) +{ + return -EOPNOTSUPP; +} + +static inline int fscrypt_decrypt_pagecache_blocks(struct page *page, + unsigned int len, + unsigned int offs) +{ + return -EOPNOTSUPP; +} + +static inline int fscrypt_decrypt_block_inplace(const struct inode *inode, + struct page *page, + unsigned int len, + unsigned int offs, u64 lblk_num) +{ + return -EOPNOTSUPP; +} + +static inline bool fscrypt_is_bounce_page(struct page *page) +{ + return false; +} + +static inline struct page *fscrypt_pagecache_page(struct page *bounce_page) +{ + WARN_ON_ONCE(1); + return ERR_PTR(-EINVAL); +} + +static inline void fscrypt_free_bounce_page(struct page *bounce_page) +{ +} + +/* policy.c */ +static inline int fscrypt_ioctl_set_policy(struct file *filp, + const void __user *arg) +{ + return -EOPNOTSUPP; +} + +static inline int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg) +{ + return -EOPNOTSUPP; +} + +static inline int fscrypt_ioctl_get_policy_ex(struct file *filp, + void __user *arg) +{ + return -EOPNOTSUPP; +} + +static inline int fscrypt_has_permitted_context(struct inode *parent, + struct inode *child) +{ + return 0; +} + +static inline int fscrypt_inherit_context(struct inode *parent, + struct inode *child, + void *fs_data, bool preload) +{ + return -EOPNOTSUPP; +} + +/* keyring.c */ +static inline void fscrypt_sb_free(struct super_block *sb) +{ +} + +static inline int fscrypt_ioctl_add_key(struct file *filp, void __user *arg) +{ + return -EOPNOTSUPP; +} + +static inline int fscrypt_ioctl_remove_key(struct file *filp, void __user *arg) +{ + return -EOPNOTSUPP; +} + +static inline int fscrypt_ioctl_remove_key_all_users(struct file *filp, + void __user *arg) +{ + return -EOPNOTSUPP; +} + +static inline int fscrypt_ioctl_get_key_status(struct file *filp, + void __user *arg) +{ + return -EOPNOTSUPP; +} + +static inline int fscrypt_register_key_removal_notifier( + struct notifier_block *nb) +{ + return 0; +} + +static inline int fscrypt_unregister_key_removal_notifier( + struct notifier_block *nb) +{ + return 0; +} + +/* keysetup.c */ +static inline int fscrypt_get_encryption_info(struct inode *inode) +{ + return -EOPNOTSUPP; +} + +static inline void fscrypt_put_encryption_info(struct inode *inode) +{ + return; +} + +static inline void fscrypt_free_inode(struct inode *inode) +{ +} + +static inline int fscrypt_drop_inode(struct inode *inode) +{ + return 0; +} + + /* fname.c */ +static inline int fscrypt_setup_filename(struct inode *dir, + const struct qstr *iname, + int lookup, struct fscrypt_name *fname) +{ + if (IS_ENCRYPTED(dir)) + return -EOPNOTSUPP; + + memset(fname, 0, sizeof(*fname)); + fname->usr_fname = iname; + fname->disk_name.name = (unsigned char *)iname->name; + fname->disk_name.len = iname->len; + return 0; +} + +static inline void fscrypt_free_filename(struct fscrypt_name *fname) +{ + return; +} + +static inline int fscrypt_fname_alloc_buffer(const struct inode *inode, + u32 max_encrypted_len, + struct fscrypt_str *crypto_str) +{ + return -EOPNOTSUPP; +} + +static inline void fscrypt_fname_free_buffer(struct fscrypt_str *crypto_str) +{ + return; +} + +static inline int fscrypt_fname_disk_to_usr(struct inode *inode, + u32 hash, u32 minor_hash, + const struct fscrypt_str *iname, + struct fscrypt_str *oname) +{ + return -EOPNOTSUPP; +} + +static inline bool fscrypt_match_name(const struct fscrypt_name *fname, + const u8 *de_name, u32 de_name_len) +{ + /* Encryption support disabled; use standard comparison */ + if (de_name_len != fname->disk_name.len) + return false; + return !memcmp(de_name, fname->disk_name.name, fname->disk_name.len); +} + +/* bio.c */ +static inline void fscrypt_decrypt_bio(struct bio *bio) +{ +} + +static inline void fscrypt_enqueue_decrypt_bio(struct fscrypt_ctx *ctx, + struct bio *bio) +{ +} + +static inline int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk, + sector_t pblk, unsigned int len) +{ + return -EOPNOTSUPP; +} + +/* hooks.c */ + +static inline int fscrypt_file_open(struct inode *inode, struct file *filp) +{ + if (IS_ENCRYPTED(inode)) + return -EOPNOTSUPP; + return 0; +} + +static inline int __fscrypt_prepare_link(struct inode *inode, struct inode *dir, + struct dentry *dentry) +{ + return -EOPNOTSUPP; +} + +static inline int __fscrypt_prepare_rename(struct inode *old_dir, + struct dentry *old_dentry, + struct inode *new_dir, + struct dentry *new_dentry, + unsigned int flags) +{ + return -EOPNOTSUPP; +} + +static inline int __fscrypt_prepare_lookup(struct inode *dir, + struct dentry *dentry, + struct fscrypt_name *fname) +{ + return -EOPNOTSUPP; +} + +static inline int __fscrypt_prepare_symlink(struct inode *dir, + unsigned int len, + unsigned int max_len, + struct fscrypt_str *disk_link) +{ + return -EOPNOTSUPP; +} + + +static inline int __fscrypt_encrypt_symlink(struct inode *inode, + const char *target, + unsigned int len, + struct fscrypt_str *disk_link) +{ + return -EOPNOTSUPP; +} + +static inline const char *fscrypt_get_symlink(struct inode *inode, + const void *caddr, + unsigned int max_size, + struct delayed_call *done) +{ + return ERR_PTR(-EOPNOTSUPP); +} +#endif /* !CONFIG_FS_ENCRYPTION */ + +/** + * fscrypt_require_key - require an inode's encryption key + * @inode: the inode we need the key for + * + * If the inode is encrypted, set up its encryption key if not already done. + * Then require that the key be present and return -ENOKEY otherwise. + * + * No locks are needed, and the key will live as long as the struct inode --- so + * it won't go away from under you. + * + * Return: 0 on success, -ENOKEY if the key is missing, or another -errno code + * if a problem occurred while setting up the encryption key. + */ +static inline int fscrypt_require_key(struct inode *inode) +{ + if (IS_ENCRYPTED(inode)) { + int err = fscrypt_get_encryption_info(inode); + + if (err) + return err; + if (!fscrypt_has_encryption_key(inode)) + return -ENOKEY; + } + return 0; +} + +/** + * fscrypt_prepare_link - prepare to link an inode into a possibly-encrypted directory + * @old_dentry: an existing dentry for the inode being linked + * @dir: the target directory + * @dentry: negative dentry for the target filename + * + * A new link can only be added to an encrypted directory if the directory's + * encryption key is available --- since otherwise we'd have no way to encrypt + * the filename. Therefore, we first set up the directory's encryption key (if + * not already done) and return an error if it's unavailable. + * + * We also verify that the link will not violate the constraint that all files + * in an encrypted directory tree use the same encryption policy. + * + * Return: 0 on success, -ENOKEY if the directory's encryption key is missing, + * -EXDEV if the link would result in an inconsistent encryption policy, or + * another -errno code. + */ +static inline int fscrypt_prepare_link(struct dentry *old_dentry, + struct inode *dir, + struct dentry *dentry) +{ + if (IS_ENCRYPTED(dir)) + return __fscrypt_prepare_link(d_inode(old_dentry), dir, dentry); + return 0; +} + +/** + * fscrypt_prepare_rename - prepare for a rename between possibly-encrypted directories + * @old_dir: source directory + * @old_dentry: dentry for source file + * @new_dir: target directory + * @new_dentry: dentry for target location (may be negative unless exchanging) + * @flags: rename flags (we care at least about %RENAME_EXCHANGE) + * + * Prepare for ->rename() where the source and/or target directories may be + * encrypted. A new link can only be added to an encrypted directory if the + * directory's encryption key is available --- since otherwise we'd have no way + * to encrypt the filename. A rename to an existing name, on the other hand, + * *is* cryptographically possible without the key. However, we take the more + * conservative approach and just forbid all no-key renames. + * + * We also verify that the rename will not violate the constraint that all files + * in an encrypted directory tree use the same encryption policy. + * + * Return: 0 on success, -ENOKEY if an encryption key is missing, -EXDEV if the + * rename would cause inconsistent encryption policies, or another -errno code. + */ +static inline int fscrypt_prepare_rename(struct inode *old_dir, + struct dentry *old_dentry, + struct inode *new_dir, + struct dentry *new_dentry, + unsigned int flags) +{ + if (IS_ENCRYPTED(old_dir) || IS_ENCRYPTED(new_dir)) + return __fscrypt_prepare_rename(old_dir, old_dentry, + new_dir, new_dentry, flags); + return 0; +} + +/** + * fscrypt_prepare_lookup - prepare to lookup a name in a possibly-encrypted directory + * @dir: directory being searched + * @dentry: filename being looked up + * @fname: (output) the name to use to search the on-disk directory + * + * Prepare for ->lookup() in a directory which may be encrypted by determining + * the name that will actually be used to search the directory on-disk. Lookups + * can be done with or without the directory's encryption key; without the key, + * filenames are presented in encrypted form. Therefore, we'll try to set up + * the directory's encryption key, but even without it the lookup can continue. + * + * This also installs a custom ->d_revalidate() method which will invalidate the + * dentry if it was created without the key and the key is later added. + * + * Return: 0 on success; -ENOENT if key is unavailable but the filename isn't a + * correctly formed encoded ciphertext name, so a negative dentry should be + * created; or another -errno code. + */ +static inline int fscrypt_prepare_lookup(struct inode *dir, + struct dentry *dentry, + struct fscrypt_name *fname) +{ + if (IS_ENCRYPTED(dir)) + return __fscrypt_prepare_lookup(dir, dentry, fname); + + memset(fname, 0, sizeof(*fname)); + fname->usr_fname = &dentry->d_name; + fname->disk_name.name = (unsigned char *)dentry->d_name.name; + fname->disk_name.len = dentry->d_name.len; + return 0; +} + +/** + * fscrypt_prepare_setattr - prepare to change a possibly-encrypted inode's attributes + * @dentry: dentry through which the inode is being changed + * @attr: attributes to change + * + * Prepare for ->setattr() on a possibly-encrypted inode. On an encrypted file, + * most attribute changes are allowed even without the encryption key. However, + * without the encryption key we do have to forbid truncates. This is needed + * because the size being truncated to may not be a multiple of the filesystem + * block size, and in that case we'd have to decrypt the final block, zero the + * portion past i_size, and re-encrypt it. (We *could* allow truncating to a + * filesystem block boundary, but it's simpler to just forbid all truncates --- + * and we already forbid all other contents modifications without the key.) + * + * Return: 0 on success, -ENOKEY if the key is missing, or another -errno code + * if a problem occurred while setting up the encryption key. + */ +static inline int fscrypt_prepare_setattr(struct dentry *dentry, + struct iattr *attr) +{ + if (attr->ia_valid & ATTR_SIZE) + return fscrypt_require_key(d_inode(dentry)); + return 0; +} + +/** + * fscrypt_prepare_symlink - prepare to create a possibly-encrypted symlink + * @dir: directory in which the symlink is being created + * @target: plaintext symlink target + * @len: length of @target excluding null terminator + * @max_len: space the filesystem has available to store the symlink target + * @disk_link: (out) the on-disk symlink target being prepared + * + * This function computes the size the symlink target will require on-disk, + * stores it in @disk_link->len, and validates it against @max_len. An + * encrypted symlink may be longer than the original. + * + * Additionally, @disk_link->name is set to @target if the symlink will be + * unencrypted, but left NULL if the symlink will be encrypted. For encrypted + * symlinks, the filesystem must call fscrypt_encrypt_symlink() to create the + * on-disk target later. (The reason for the two-step process is that some + * filesystems need to know the size of the symlink target before creating the + * inode, e.g. to determine whether it will be a "fast" or "slow" symlink.) + * + * Return: 0 on success, -ENAMETOOLONG if the symlink target is too long, + * -ENOKEY if the encryption key is missing, or another -errno code if a problem + * occurred while setting up the encryption key. + */ +static inline int fscrypt_prepare_symlink(struct inode *dir, + const char *target, + unsigned int len, + unsigned int max_len, + struct fscrypt_str *disk_link) +{ + if (IS_ENCRYPTED(dir) || fscrypt_dummy_context_enabled(dir)) + return __fscrypt_prepare_symlink(dir, len, max_len, disk_link); + + disk_link->name = (unsigned char *)target; + disk_link->len = len + 1; + if (disk_link->len > max_len) + return -ENAMETOOLONG; + return 0; +} + +/** + * fscrypt_encrypt_symlink - encrypt the symlink target if needed + * @inode: symlink inode + * @target: plaintext symlink target + * @len: length of @target excluding null terminator + * @disk_link: (in/out) the on-disk symlink target being prepared + * + * If the symlink target needs to be encrypted, then this function encrypts it + * into @disk_link->name. fscrypt_prepare_symlink() must have been called + * previously to compute @disk_link->len. If the filesystem did not allocate a + * buffer for @disk_link->name after calling fscrypt_prepare_link(), then one + * will be kmalloc()'ed and the filesystem will be responsible for freeing it. + * + * Return: 0 on success, -errno on failure + */ +static inline int fscrypt_encrypt_symlink(struct inode *inode, + const char *target, + unsigned int len, + struct fscrypt_str *disk_link) +{ + if (IS_ENCRYPTED(inode)) + return __fscrypt_encrypt_symlink(inode, target, len, disk_link); + return 0; +} + +/* If *pagep is a bounce page, free it and set *pagep to the pagecache page */ +static inline void fscrypt_finalize_bounce_page(struct page **pagep) +{ + struct page *page = *pagep; + + if (fscrypt_is_bounce_page(page)) { + *pagep = fscrypt_pagecache_page(page); + fscrypt_free_bounce_page(page); + } +} + +#endif /* _LINUX_FSCRYPT_H */ |