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fscrypt: define fscrypt_fname_alloc_buffer() to be for presented names

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Previously fscrypt_fname_alloc_buffer() was used to allocate buffers for
both presented (decrypted or encoded) and encrypted filenames.  That was
confusing, because it had to allocate the worst-case size for either,
e.g. including NUL-padding even when it was meaningless.

But now that fscrypt_setup_filename() no longer calls it, it is only
used in the ->get_link() and ->readdir() paths, which specifically want
a buffer for presented filenames.  Therefore, switch the behavior over
to allocating the buffer for presented filenames only.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Eric Biggers 2018-01-11 23:30:08 -05:00 committed by Theodore Ts'o
parent 50c961de59
commit 2cbadadcfd
2 changed files with 15 additions and 16 deletions
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29
fs/crypto/fname.c
View File

@ -204,37 +204,36 @@ u32 fscrypt_fname_encrypted_size(const struct inode *inode, u32 ilen)
EXPORT_SYMBOL(fscrypt_fname_encrypted_size);
/**
* fscrypt_fname_crypto_alloc_obuff() -
* fscrypt_fname_alloc_buffer - allocate a buffer for presented filenames
*
* Allocates an output buffer that is sufficient for the crypto operation
* specified by the context and the direction.
* Allocate a buffer that is large enough to hold any decrypted or encoded
* filename (null-terminated), for the given maximum encrypted filename length.
*
* Return: 0 on success, -errno on failure
*/
int fscrypt_fname_alloc_buffer(const struct inode *inode,
u32 ilen, struct fscrypt_str *crypto_str)
u32 max_encrypted_len,
struct fscrypt_str *crypto_str)
{
u32 olen = fscrypt_fname_encrypted_size(inode, ilen);
const u32 max_encoded_len =
max_t(u32, BASE64_CHARS(FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE),
1 + BASE64_CHARS(sizeof(struct fscrypt_digested_name)));
u32 max_presented_len;
crypto_str->len = olen;
olen = max(olen, max_encoded_len);
max_presented_len = max(max_encoded_len, max_encrypted_len);
/*
* Allocated buffer can hold one more character to null-terminate the
* string
*/
crypto_str->name = kmalloc(olen + 1, GFP_NOFS);
if (!(crypto_str->name))
crypto_str->name = kmalloc(max_presented_len + 1, GFP_NOFS);
if (!crypto_str->name)
return -ENOMEM;
crypto_str->len = max_presented_len;
return 0;
}
EXPORT_SYMBOL(fscrypt_fname_alloc_buffer);
/**
* fscrypt_fname_crypto_free_buffer() -
* fscrypt_fname_free_buffer - free the buffer for presented filenames
*
* Frees the buffer allocated for crypto operation.
* Free the buffer allocated by fscrypt_fname_alloc_buffer().
*/
void fscrypt_fname_free_buffer(struct fscrypt_str *crypto_str)
{

2
include/linux/fscrypt_notsupp.h
View File

@ -140,7 +140,7 @@ static inline u32 fscrypt_fname_encrypted_size(const struct inode *inode,
}
static inline int fscrypt_fname_alloc_buffer(const struct inode *inode,
u32 ilen,
u32 max_encrypted_len,
struct fscrypt_str *crypto_str)
{
return -EOPNOTSUPP;