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

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: default avatarDavid Gstir <david@sigma-star.at>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 9e532772

fs/crypto/crypto.c

+52 −41
Original line number Diff line number Diff line
@@ -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
@@ -215,43 +217,52 @@ 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.

 * @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.

 * @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.

 * @index: Index for encryption.

 * @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);

include/linux/fscrypto.h

+4 −4
Original line number Diff line number Diff line
@@ -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;

}