Commit 1400451f authored by David Gstir's avatar David Gstir Committed by Theodore Ts'o

fscrypt: Cleanup fscrypt_{decrypt,encrypt}_page()

- Improve documentation
- Add BUG_ON(len == 0) to avoid accidental switch of offs and len
parameters
- Improve variable names for readability
Signed-off-by: David Gstir's avatarDavid Gstir <david@sigma-star.at>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 9e532772
......@@ -147,9 +147,9 @@ typedef enum {
} fscrypt_direction_t;
static int do_page_crypto(const struct inode *inode,
fscrypt_direction_t rw, pgoff_t index,
fscrypt_direction_t rw, u64 lblk_num,
struct page *src_page, struct page *dest_page,
unsigned int src_len, unsigned int src_offset,
unsigned int len, unsigned int offs,
gfp_t gfp_flags)
{
struct {
......@@ -163,6 +163,8 @@ static int do_page_crypto(const struct inode *inode,
struct crypto_skcipher *tfm = ci->ci_ctfm;
int res = 0;
BUG_ON(len == 0);
req = skcipher_request_alloc(tfm, gfp_flags);
if (!req) {
printk_ratelimited(KERN_ERR
......@@ -176,14 +178,14 @@ static int do_page_crypto(const struct inode *inode,
page_crypt_complete, &ecr);
BUILD_BUG_ON(sizeof(xts_tweak) != FS_XTS_TWEAK_SIZE);
xts_tweak.index = cpu_to_le64(index);
xts_tweak.index = cpu_to_le64(lblk_num);
memset(xts_tweak.padding, 0, sizeof(xts_tweak.padding));
sg_init_table(&dst, 1);
sg_set_page(&dst, dest_page, src_len, src_offset);
sg_set_page(&dst, dest_page, len, offs);
sg_init_table(&src, 1);
sg_set_page(&src, src_page, src_len, src_offset);
skcipher_request_set_crypt(req, &src, &dst, src_len, &xts_tweak);
sg_set_page(&src, src_page, len, offs);
skcipher_request_set_crypt(req, &src, &dst, len, &xts_tweak);
if (rw == FS_DECRYPT)
res = crypto_skcipher_decrypt(req);
else
......@@ -214,44 +216,53 @@ static struct page *alloc_bounce_page(struct fscrypt_ctx *ctx, gfp_t gfp_flags)
/**
* fscypt_encrypt_page() - Encrypts a page
* @inode: The inode for which the encryption should take place
* @plaintext_page: The page to encrypt. Must be locked.
* @plaintext_len: Length of plaintext within page
* @plaintext_offset: Offset of plaintext within page
* @index: Index for encryption. This is mainly the page index, but
* but might be different for multiple calls on same page.
* @gfp_flags: The gfp flag for memory allocation
* @inode: The inode for which the encryption should take place
* @page: The page to encrypt. Must be locked for bounce-page
* encryption.
* @len: Length of data to encrypt in @page and encrypted
* data in returned page.
* @offs: Offset of data within @page and returned
* page holding encrypted data.
* @lblk_num: Logical block number. This must be unique for multiple
* calls with same inode, except when overwriting
* previously written data.
* @gfp_flags: The gfp flag for memory allocation
*
* Encrypts plaintext_page using the ctx encryption context. If
* the filesystem supports it, encryption is performed in-place, otherwise a
* new ciphertext_page is allocated and returned.
* Encrypts @page using the ctx encryption context. Performs encryption
* either in-place or into a newly allocated bounce page.
* Called on the page write path.
*
* Called on the page write path. The caller must call
* Bounce page allocation is the default.
* In this case, the contents of @page are encrypted and stored in an
* allocated bounce page. @page has to be locked and the caller must call
* fscrypt_restore_control_page() on the returned ciphertext page to
* release the bounce buffer and the encryption context.
*
* Return: An allocated page with the encrypted content on success. Else, an
* In-place encryption is used by setting the FS_CFLG_INPLACE_ENCRYPTION flag in
* fscrypt_operations. Here, the input-page is returned with its content
* encrypted.
*
* Return: A page with the encrypted content on success. Else, an
* error value or NULL.
*/
struct page *fscrypt_encrypt_page(const struct inode *inode,
struct page *plaintext_page,
unsigned int plaintext_len,
unsigned int plaintext_offset,
pgoff_t index, gfp_t gfp_flags)
struct page *page,
unsigned int len,
unsigned int offs,
u64 lblk_num, gfp_t gfp_flags)
{
struct fscrypt_ctx *ctx;
struct page *ciphertext_page = plaintext_page;
struct page *ciphertext_page = page;
int err;
BUG_ON(plaintext_len % FS_CRYPTO_BLOCK_SIZE != 0);
BUG_ON(len % FS_CRYPTO_BLOCK_SIZE != 0);
if (inode->i_sb->s_cop->flags & FS_CFLG_INPLACE_ENCRYPTION) {
/* with inplace-encryption we just encrypt the page */
err = do_page_crypto(inode, FS_ENCRYPT, index,
plaintext_page, ciphertext_page,
plaintext_len, plaintext_offset,
gfp_flags);
err = do_page_crypto(inode, FS_ENCRYPT, lblk_num,
page, ciphertext_page,
len, offs, gfp_flags);
if (err)
return ERR_PTR(err);
......@@ -267,11 +278,10 @@ struct page *fscrypt_encrypt_page(const struct inode *inode,
if (IS_ERR(ciphertext_page))
goto errout;
ctx->w.control_page = plaintext_page;
err = do_page_crypto(inode, FS_ENCRYPT, index,
plaintext_page, ciphertext_page,
plaintext_len, plaintext_offset,
gfp_flags);
ctx->w.control_page = page;
err = do_page_crypto(inode, FS_ENCRYPT, lblk_num,
page, ciphertext_page,
len, offs, gfp_flags);
if (err) {
ciphertext_page = ERR_PTR(err);
goto errout;
......@@ -289,11 +299,12 @@ EXPORT_SYMBOL(fscrypt_encrypt_page);
/**
* fscrypt_decrypt_page() - Decrypts a page in-place
* @inode: Encrypted inode to decrypt.
* @page: The page to decrypt. Must be locked.
* @len: Number of bytes in @page to be decrypted.
* @offs: Start of data in @page.
* @index: Index for encryption.
* @inode: The corresponding inode for the page to decrypt.
* @page: The page to decrypt. Must be locked in case
* it is a writeback page.
* @len: Number of bytes in @page to be decrypted.
* @offs: Start of data in @page.
* @lblk_num: Logical block number.
*
* Decrypts page in-place using the ctx encryption context.
*
......@@ -302,10 +313,10 @@ EXPORT_SYMBOL(fscrypt_encrypt_page);
* Return: Zero on success, non-zero otherwise.
*/
int fscrypt_decrypt_page(const struct inode *inode, struct page *page,
unsigned int len, unsigned int offs, pgoff_t index)
unsigned int len, unsigned int offs, u64 lblk_num)
{
return do_page_crypto(inode, FS_DECRYPT, index, page, page, len, offs,
GFP_NOFS);
return do_page_crypto(inode, FS_DECRYPT, lblk_num, page, page, len,
offs, GFP_NOFS);
}
EXPORT_SYMBOL(fscrypt_decrypt_page);
......
......@@ -173,9 +173,9 @@ extern struct fscrypt_ctx *fscrypt_get_ctx(const struct inode *, gfp_t);
extern void fscrypt_release_ctx(struct fscrypt_ctx *);
extern struct page *fscrypt_encrypt_page(const struct inode *, struct page *,
unsigned int, unsigned int,
pgoff_t, gfp_t);
u64, gfp_t);
extern int fscrypt_decrypt_page(const struct inode *, struct page *, unsigned int,
unsigned int, pgoff_t);
unsigned int, u64);
extern void fscrypt_decrypt_bio_pages(struct fscrypt_ctx *, struct bio *);
extern void fscrypt_pullback_bio_page(struct page **, bool);
extern void fscrypt_restore_control_page(struct page *);
......@@ -221,14 +221,14 @@ static inline struct page *fscrypt_notsupp_encrypt_page(const struct inode *i,
struct page *p,
unsigned int len,
unsigned int offs,
pgoff_t index, gfp_t f)
u64 lblk_num, gfp_t f)
{
return ERR_PTR(-EOPNOTSUPP);
}
static inline int fscrypt_notsupp_decrypt_page(const struct inode *i, struct page *p,
unsigned int len, unsigned int offs,
pgoff_t index)
u64 lblk_num)
{
return -EOPNOTSUPP;
}
......
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