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Message-ID: <20071221150145.GE10989@localhost.austin.ibm.com>
Date: Fri, 21 Dec 2007 09:01:45 -0600
From: Michael Halcrow <mhalcrow@...ibm.com>
To: Eric Sandeen <sandeen@...hat.com>
Cc: linux-kernel Mailing List <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>, mike@...crow.us,
Jeff Moyer <jmoyer@...hat.com>
Subject: Re: [PATCH] ecryptfs: check for existing key_tfm at mount time
On Thu, Dec 20, 2007 at 11:18:49PM -0600, Eric Sandeen wrote:
> 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.
>
> Signed-off-by: Eric Sandeen <sandeen@...hat.com>
Acked-by: Mike Halcrow <mhalcrow@...ibm.com>
> ---
>
> Index: linux-2.6.24-rc3/fs/ecryptfs/crypto.c
> ===================================================================
> --- linux-2.6.24-rc3.orig/fs/ecryptfs/crypto.c
> +++ linux-2.6.24-rc3/fs/ecryptfs/crypto.c
> @@ -1868,6 +1868,33 @@ 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
> + *
> + * Returns 1 if found, with key_tfm set
> + * Returns 0 if not found, 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;
> +
> + mutex_lock(&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) {
> + mutex_unlock(&key_tfm_list_mutex);
> + if (key_tfm)
> + (*key_tfm) = tmp_key_tfm;
> + return 1;
> + }
> + }
> + mutex_unlock(&key_tfm_list_mutex);
> + if (key_tfm)
> + (*key_tfm) = NULL;
> + return 0;
> +}
> +
> int ecryptfs_get_tfm_and_mutex_for_cipher_name(struct crypto_blkcipher **tfm,
> struct mutex **tfm_mutex,
> char *cipher_name)
> @@ -1877,22 +1904,15 @@ int ecryptfs_get_tfm_and_mutex_for_ciphe
>
> (*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:
> Index: linux-2.6.24-rc3/fs/ecryptfs/ecryptfs_kernel.h
> ===================================================================
> --- linux-2.6.24-rc3.orig/fs/ecryptfs/ecryptfs_kernel.h
> +++ linux-2.6.24-rc3/fs/ecryptfs/ecryptfs_kernel.h
> @@ -623,6 +623,7 @@ ecryptfs_add_new_key_tfm(struct ecryptfs
> 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);
> Index: linux-2.6.24-rc3/fs/ecryptfs/main.c
> ===================================================================
> --- linux-2.6.24-rc3.orig/fs/ecryptfs/main.c
> +++ linux-2.6.24-rc3/fs/ecryptfs/main.c
> @@ -410,9 +410,11 @@ static int ecryptfs_parse_options(struct
> 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);
> + 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);
> if (rc) {
> printk(KERN_ERR "Error attempting to initialize cipher with "
> "name = [%s] and key size = [%td]; rc = [%d]\n",
>
--
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