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fscrypt: Add in-place encryption mode 

ext4 and f2fs require a bounce page when encrypting pages. However, not
all filesystems will need that (eg. UBIFS). This is handled via a
flag on fscrypt_operations where a fs implementation can select in-place
encryption over using a bounce page (which is the default).

Signed-off-by: David Gstir <david@sigma-star.at>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
David Gstir 2016-11-13 22:20:44 +01:00 committed by Theodore Ts'o
parent bc33b0ca11
commit 1c7dcf69ee
2 changed files with 21 additions and 10 deletions
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25
fs/crypto/crypto.c
View File

@ -217,8 +217,9 @@ static struct page *alloc_bounce_page(struct fscrypt_ctx *ctx, gfp_t gfp_flags)
* @plaintext_page: The page to encrypt. Must be locked. * @plaintext_page: The page to encrypt. Must be locked.
* @gfp_flags: The gfp flag for memory allocation * @gfp_flags: The gfp flag for memory allocation
* *
* Allocates a ciphertext page and encrypts plaintext_page into it using the ctx * Encrypts plaintext_page using the ctx encryption context. If
* encryption context. * the filesystem supports it, encryption is performed in-place, otherwise a
* new ciphertext_page is allocated and returned.
* *
* Called on the page write path. The caller must call * Called on the page write path. The caller must call
* fscrypt_restore_control_page() on the returned ciphertext page to * fscrypt_restore_control_page() on the returned ciphertext page to
@ -231,7 +232,7 @@ struct page *fscrypt_encrypt_page(struct inode *inode,
struct page *plaintext_page, gfp_t gfp_flags) struct page *plaintext_page, gfp_t gfp_flags)
{ {
struct fscrypt_ctx *ctx; struct fscrypt_ctx *ctx;
struct page *ciphertext_page = NULL; struct page *ciphertext_page = plaintext_page;
int err; int err;
BUG_ON(!PageLocked(plaintext_page)); BUG_ON(!PageLocked(plaintext_page));
@ -240,10 +241,12 @@ struct page *fscrypt_encrypt_page(struct inode *inode,
if (IS_ERR(ctx)) if (IS_ERR(ctx))
return (struct page *)ctx; return (struct page *)ctx;
/* The encryption operation will require a bounce page. */ if (!(inode->i_sb->s_cop->flags & FS_CFLG_INPLACE_ENCRYPTION)) {
ciphertext_page = alloc_bounce_page(ctx, gfp_flags); /* The encryption operation will require a bounce page. */
if (IS_ERR(ciphertext_page)) ciphertext_page = alloc_bounce_page(ctx, gfp_flags);
goto errout; if (IS_ERR(ciphertext_page))
goto errout;
}
ctx->w.control_page = plaintext_page; ctx->w.control_page = plaintext_page;
err = do_page_crypto(inode, FS_ENCRYPT, plaintext_page->index, err = do_page_crypto(inode, FS_ENCRYPT, plaintext_page->index,
@ -253,9 +256,11 @@ struct page *fscrypt_encrypt_page(struct inode *inode,
ciphertext_page = ERR_PTR(err); ciphertext_page = ERR_PTR(err);
goto errout; goto errout;
} }
SetPagePrivate(ciphertext_page); if (!(inode->i_sb->s_cop->flags & FS_CFLG_INPLACE_ENCRYPTION)) {
set_page_private(ciphertext_page, (unsigned long)ctx); SetPagePrivate(ciphertext_page);
lock_page(ciphertext_page); set_page_private(ciphertext_page, (unsigned long)ctx);
lock_page(ciphertext_page);
}
return ciphertext_page; return ciphertext_page;
errout: errout:

6
include/linux/fscrypto.h
View File

@ -153,10 +153,16 @@ struct fscrypt_name {
#define fname_name(p) ((p)->disk_name.name) #define fname_name(p) ((p)->disk_name.name)
#define fname_len(p) ((p)->disk_name.len) #define fname_len(p) ((p)->disk_name.len)
/*
* fscrypt superblock flags
*/
#define FS_CFLG_INPLACE_ENCRYPTION (1U << 1)
/* /*
* crypto opertions for filesystems * crypto opertions for filesystems
*/ */
struct fscrypt_operations { struct fscrypt_operations {
unsigned int flags;
int (*get_context)(struct inode *, void *, size_t); int (*get_context)(struct inode *, void *, size_t);
int (*key_prefix)(struct inode *, u8 **); int (*key_prefix)(struct inode *, u8 **);
int (*prepare_context)(struct inode *); int (*prepare_context)(struct inode *);