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ecryptfs: check for existing key_tfm at mount time 

Jeff Moyer pointed out that a mount; umount loop of ecryptfs, with the same
cipher & other mount options, created a new ecryptfs_key_tfm_cache item
each time, and the cache could grow quite large this way.

Looking at this with mhalcrow, we saw that ecryptfs_parse_options()
unconditionally called ecryptfs_add_new_key_tfm(), which is what was adding
these items.

Refactor ecryptfs_get_tfm_and_mutex_for_cipher_name() to create a new
helper function, ecryptfs_tfm_exists(), which checks for the cipher on the
cached key_tfm_list, and sets a pointer to it if it exists.  This can then
be called from ecryptfs_parse_options(), and new key_tfm's can be added
only when a cached one is not found.

With list locking changes suggested by akpm.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Cc: Michael Halcrow <mhalcrow@us.ibm.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Eric Sandeen 2008-02-06 01:38:37 -08:00 committed by Linus Torvalds
parent 19e66a67e9
commit af440f5292
3 changed files with 63 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

67
fs/ecryptfs/crypto.c
View File

@ -1779,7 +1779,7 @@ out:
struct kmem_cache *ecryptfs_key_tfm_cache;
static struct list_head key_tfm_list;
static struct mutex key_tfm_list_mutex;
struct mutex key_tfm_list_mutex;
int ecryptfs_init_crypto(void)
{
@ -1788,6 +1788,11 @@ int ecryptfs_init_crypto(void)
return 0;
}
/**
* ecryptfs_destroy_crypto - free all cached key_tfms on key_tfm_list
*
* Called only at module unload time
*/
int ecryptfs_destroy_crypto(void)
{
struct ecryptfs_key_tfm *key_tfm, *key_tfm_tmp;
@ -1811,6 +1816,8 @@ ecryptfs_add_new_key_tfm(struct ecryptfs_key_tfm **key_tfm, char *cipher_name,
struct ecryptfs_key_tfm *tmp_tfm;
int rc = 0;
BUG_ON(!mutex_is_locked(&key_tfm_list_mutex));
tmp_tfm = kmem_cache_alloc(ecryptfs_key_tfm_cache, GFP_KERNEL);
if (key_tfm != NULL)
(*key_tfm) = tmp_tfm;
@ -1837,13 +1844,50 @@ ecryptfs_add_new_key_tfm(struct ecryptfs_key_tfm **key_tfm, char *cipher_name,
(*key_tfm) = NULL;
goto out;
}
mutex_lock(&key_tfm_list_mutex);
list_add(&tmp_tfm->key_tfm_list, &key_tfm_list);
mutex_unlock(&key_tfm_list_mutex);
out:
return rc;
}
/**
* ecryptfs_tfm_exists - Search for existing tfm for cipher_name.
* @cipher_name: the name of the cipher to search for
* @key_tfm: set to corresponding tfm if found
*
* Searches for cached key_tfm matching @cipher_name
* Must be called with &key_tfm_list_mutex held
* Returns 1 if found, with @key_tfm set
* Returns 0 if not found, with @key_tfm set to NULL
*/
int ecryptfs_tfm_exists(char *cipher_name, struct ecryptfs_key_tfm **key_tfm)
{
struct ecryptfs_key_tfm *tmp_key_tfm;
BUG_ON(!mutex_is_locked(&key_tfm_list_mutex));
list_for_each_entry(tmp_key_tfm, &key_tfm_list, key_tfm_list) {
if (strcmp(tmp_key_tfm->cipher_name, cipher_name) == 0) {
if (key_tfm)
(*key_tfm) = tmp_key_tfm;
return 1;
}
}
if (key_tfm)
(*key_tfm) = NULL;
return 0;
}
/**
* ecryptfs_get_tfm_and_mutex_for_cipher_name
*
* @tfm: set to cached tfm found, or new tfm created
* @tfm_mutex: set to mutex for cached tfm found, or new tfm created
* @cipher_name: the name of the cipher to search for and/or add
*
* Sets pointers to @tfm & @tfm_mutex matching @cipher_name.
* Searches for cached item first, and creates new if not found.
* Returns 0 on success, non-zero if adding new cipher failed
*/
int ecryptfs_get_tfm_and_mutex_for_cipher_name(struct crypto_blkcipher **tfm,
struct mutex **tfm_mutex,
char *cipher_name)
@ -1853,22 +1897,17 @@ int ecryptfs_get_tfm_and_mutex_for_cipher_name(struct crypto_blkcipher **tfm,
(*tfm) = NULL;
(*tfm_mutex) = NULL;
mutex_lock(&key_tfm_list_mutex);
list_for_each_entry(key_tfm, &key_tfm_list, key_tfm_list) {
if (strcmp(key_tfm->cipher_name, cipher_name) == 0) {
(*tfm) = key_tfm->key_tfm;
(*tfm_mutex) = &key_tfm->key_tfm_mutex;
mutex_unlock(&key_tfm_list_mutex);
if (!ecryptfs_tfm_exists(cipher_name, &key_tfm)) {
rc = ecryptfs_add_new_key_tfm(&key_tfm, cipher_name, 0);
if (rc) {
printk(KERN_ERR "Error adding new key_tfm to list; "
"rc = [%d]\n", rc);
goto out;
}
}
mutex_unlock(&key_tfm_list_mutex);
rc = ecryptfs_add_new_key_tfm(&key_tfm, cipher_name, 0);
if (rc) {
printk(KERN_ERR "Error adding new key_tfm to list; rc = [%d]\n",
rc);
goto out;
}
(*tfm) = key_tfm->key_tfm;
(*tfm_mutex) = &key_tfm->key_tfm_mutex;
out:

3
fs/ecryptfs/ecryptfs_kernel.h
View File

@ -323,6 +323,8 @@ struct ecryptfs_key_tfm {
unsigned char cipher_name[ECRYPTFS_MAX_CIPHER_NAME_SIZE + 1];
};
extern struct mutex key_tfm_list_mutex;
/**
* This struct is to enable a mount-wide passphrase/salt combo. This
* is more or less a stopgap to provide similar functionality to other
@ -617,6 +619,7 @@ ecryptfs_add_new_key_tfm(struct ecryptfs_key_tfm **key_tfm, char *cipher_name,
size_t key_size);
int ecryptfs_init_crypto(void);
int ecryptfs_destroy_crypto(void);
int ecryptfs_tfm_exists(char *cipher_name, struct ecryptfs_key_tfm **key_tfm);
int ecryptfs_get_tfm_and_mutex_for_cipher_name(struct crypto_blkcipher **tfm,
struct mutex **tfm_mutex,
char *cipher_name);

10
fs/ecryptfs/main.c
View File

@ -410,9 +410,13 @@ static int ecryptfs_parse_options(struct super_block *sb, char *options)
if (!cipher_key_bytes_set) {
mount_crypt_stat->global_default_cipher_key_size = 0;
}
rc = ecryptfs_add_new_key_tfm(
NULL, mount_crypt_stat->global_default_cipher_name,
mount_crypt_stat->global_default_cipher_key_size);
mutex_lock(&key_tfm_list_mutex);
if (!ecryptfs_tfm_exists(mount_crypt_stat->global_default_cipher_name,
NULL))
rc = ecryptfs_add_new_key_tfm(
NULL, mount_crypt_stat->global_default_cipher_name,
mount_crypt_stat->global_default_cipher_key_size);
mutex_unlock(&key_tfm_list_mutex);
if (rc) {
printk(KERN_ERR "Error attempting to initialize cipher with "
"name = [%s] and key size = [%td]; rc = [%d]\n",