fscrypt: fix up fscrypt_fname_encrypted_size() for internal use
Filesystems don't need fscrypt_fname_encrypted_size() anymore, so
unexport it and move it to fscrypt_private.h.
We also never calculate the encrypted size of a filename without having
the fscrypt_info present since it is needed to know the amount of
NUL-padding which is determined by the encryption policy, and also we
will always truncate the NUL-padding to the maximum filename length.
Therefore, also make fscrypt_fname_encrypted_size() assume that the
fscrypt_info is present, and make it truncate the returned length to the
specified max_len.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c
index 44ddd09..e33f3d3 100644
--- a/fs/crypto/fname.c
+++ b/fs/crypto/fname.c
@@ -191,17 +191,20 @@ static int digest_decode(const char *src, int len, char *dst)
return cp - dst;
}
-u32 fscrypt_fname_encrypted_size(const struct inode *inode, u32 ilen)
+bool fscrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len,
+ u32 max_len, u32 *encrypted_len_ret)
{
- int padding = 32;
- struct fscrypt_info *ci = inode->i_crypt_info;
+ int padding = 4 << (inode->i_crypt_info->ci_flags &
+ FS_POLICY_FLAGS_PAD_MASK);
+ u32 encrypted_len;
- if (ci)
- padding = 4 << (ci->ci_flags & FS_POLICY_FLAGS_PAD_MASK);
- ilen = max(ilen, (u32)FS_CRYPTO_BLOCK_SIZE);
- return round_up(ilen, padding);
+ if (orig_len > max_len)
+ return false;
+ encrypted_len = max(orig_len, (u32)FS_CRYPTO_BLOCK_SIZE);
+ encrypted_len = round_up(encrypted_len, padding);
+ *encrypted_len_ret = min(encrypted_len, max_len);
+ return true;
}
-EXPORT_SYMBOL(fscrypt_fname_encrypted_size);
/**
* fscrypt_fname_alloc_buffer - allocate a buffer for presented filenames
@@ -342,14 +345,10 @@ int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
return ret;
if (dir->i_crypt_info) {
- unsigned int max_len = dir->i_sb->s_cop->max_namelen(dir);
-
- if (iname->len > max_len)
+ if (!fscrypt_fname_encrypted_size(dir, iname->len,
+ dir->i_sb->s_cop->max_namelen(dir),
+ &fname->crypto_buf.len))
return -ENAMETOOLONG;
-
- fname->crypto_buf.len =
- min(fscrypt_fname_encrypted_size(dir, iname->len),
- max_len);
fname->crypto_buf.name = kmalloc(fname->crypto_buf.len,
GFP_NOFS);
if (!fname->crypto_buf.name)
diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index 0539175..ad6722b 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -110,6 +110,9 @@ extern struct page *fscrypt_alloc_bounce_page(struct fscrypt_ctx *ctx,
/* fname.c */
extern int fname_encrypt(struct inode *inode, const struct qstr *iname,
u8 *out, unsigned int olen);
+extern bool fscrypt_fname_encrypted_size(const struct inode *inode,
+ u32 orig_len, u32 max_len,
+ u32 *encrypted_len_ret);
/* keyinfo.c */
extern void __exit fscrypt_essiv_cleanup(void);
diff --git a/fs/crypto/hooks.c b/fs/crypto/hooks.c
index 5bf38d9..28f9f05 100644
--- a/fs/crypto/hooks.c
+++ b/fs/crypto/hooks.c
@@ -143,12 +143,12 @@ int __fscrypt_prepare_symlink(struct inode *dir, unsigned int len,
* counting it (even though it is meaningless for ciphertext) is simpler
* for now since filesystems will assume it is there and subtract it.
*/
- if (sizeof(struct fscrypt_symlink_data) + len > max_len)
+ if (!fscrypt_fname_encrypted_size(dir, len,
+ max_len - sizeof(struct fscrypt_symlink_data),
+ &disk_link->len))
return -ENAMETOOLONG;
- disk_link->len = min_t(unsigned int,
- sizeof(struct fscrypt_symlink_data) +
- fscrypt_fname_encrypted_size(dir, len),
- max_len);
+ disk_link->len += sizeof(struct fscrypt_symlink_data);
+
disk_link->name = NULL;
return 0;
}