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SubjectRe: [PATCH 4/5] eCryptfs: move ecryptfs_find_auth_tok_for_sig() call before mutex_lock
On Thu Mar 17, 2011 at 12:48:53PM +0100, Roberto Sassu <roberto.sassu@polito.it> wrote:
> The ecryptfs_find_auth_tok_for_sig() call is moved before the
> mutex_lock(s->tfm_mutex) instruction in order to avoid possible deadlocks
> that may occur by holding the lock on the two semaphores 'key->sem' and
> 's->tfm_mutex' in reverse order.
>
> Signed-off-by: Roberto Sassu <roberto.sassu@polito.it>
> ---
> fs/ecryptfs/keystore.c | 42 +++++++++++++++++++++++-------------------
> 1 files changed, 23 insertions(+), 19 deletions(-)
>
> diff --git a/fs/ecryptfs/keystore.c b/fs/ecryptfs/keystore.c
> index e35d745..d066217 100644
> --- a/fs/ecryptfs/keystore.c
> +++ b/fs/ecryptfs/keystore.c
> @@ -538,6 +538,7 @@ ecryptfs_write_tag_70_packet(char *dest, size_t *remaining_bytes,
> char *filename, size_t filename_size)
> {
> struct ecryptfs_write_tag_70_packet_silly_stack *s;
> + struct ecryptfs_auth_tok *auth_tok;

Why declare a new ecryptfs_auth_tok struct pointer here? The idea behind
the ecryptfs_write_tag_70_packet_silly_stack struct is to keep stack
size at a minimum. Since it already has s->auth_tok, I don't see why we
would need to declare a new one.

> struct key *auth_tok_key = NULL;
> int rc = 0;
>
> @@ -550,6 +551,16 @@ ecryptfs_write_tag_70_packet(char *dest, size_t *remaining_bytes,
> }
> s->desc.flags = CRYPTO_TFM_REQ_MAY_SLEEP;
> (*packet_size) = 0;
> + rc = ecryptfs_find_auth_tok_for_sig(
> + &auth_tok_key,
> + &auth_tok, mount_crypt_stat,
> + mount_crypt_stat->global_default_fnek_sig);
> + if (rc) {
> + printk(KERN_ERR "%s: Error attempting to find auth tok for "
> + "fnek sig [%s]; rc = [%d]\n", __func__,
> + mount_crypt_stat->global_default_fnek_sig, rc);
> + goto out;
> + }
> rc = ecryptfs_get_tfm_and_mutex_for_cipher_name(
> &s->desc.tfm,
> &s->tfm_mutex, mount_crypt_stat->global_default_fn_cipher_name);
> @@ -635,16 +646,7 @@ ecryptfs_write_tag_70_packet(char *dest, size_t *remaining_bytes,
> goto out_free_unlock;
> }
> dest[s->i++] = s->cipher_code;
> - rc = ecryptfs_find_auth_tok_for_sig(
> - &auth_tok_key,
> - &s->auth_tok, mount_crypt_stat,
> - mount_crypt_stat->global_default_fnek_sig);
> - if (rc) {
> - printk(KERN_ERR "%s: Error attempting to find auth tok for "
> - "fnek sig [%s]; rc = [%d]\n", __func__,
> - mount_crypt_stat->global_default_fnek_sig, rc);
> - goto out_free_unlock;
> - }
> + s->auth_tok = auth_tok;
> /* TODO: Support other key modules than passphrase for
> * filename encryption */
> if (s->auth_tok->token_type != ECRYPTFS_PASSWORD) {
> @@ -831,6 +833,7 @@ ecryptfs_parse_tag_70_packet(char **filename, size_t *filename_size,
> char *data, size_t max_packet_size)
> {
> struct ecryptfs_parse_tag_70_packet_silly_stack *s;
> + struct ecryptfs_auth_tok *auth_tok;

Same here as above.

Tyler

> struct key *auth_tok_key = NULL;
> int rc = 0;
>
> @@ -898,6 +901,15 @@ ecryptfs_parse_tag_70_packet(char **filename, size_t *filename_size,
> __func__, s->cipher_code);
> goto out;
> }
> + rc = ecryptfs_find_auth_tok_for_sig(&auth_tok_key,
> + &auth_tok, mount_crypt_stat,
> + s->fnek_sig_hex);
> + if (rc) {
> + printk(KERN_ERR "%s: Error attempting to find auth tok for "
> + "fnek sig [%s]; rc = [%d]\n", __func__, s->fnek_sig_hex,
> + rc);
> + goto out;
> + }
> rc = ecryptfs_get_tfm_and_mutex_for_cipher_name(&s->desc.tfm,
> &s->tfm_mutex,
> s->cipher_string);
> @@ -944,15 +956,7 @@ ecryptfs_parse_tag_70_packet(char **filename, size_t *filename_size,
> * >= ECRYPTFS_MAX_IV_BYTES. */
> memset(s->iv, 0, ECRYPTFS_MAX_IV_BYTES);
> s->desc.info = s->iv;
> - rc = ecryptfs_find_auth_tok_for_sig(&auth_tok_key,
> - &s->auth_tok, mount_crypt_stat,
> - s->fnek_sig_hex);
> - if (rc) {
> - printk(KERN_ERR "%s: Error attempting to find auth tok for "
> - "fnek sig [%s]; rc = [%d]\n", __func__, s->fnek_sig_hex,
> - rc);
> - goto out_free_unlock;
> - }
> + s->auth_tok = auth_tok;
> /* TODO: Support other key modules than passphrase for
> * filename encryption */
> if (s->auth_tok->token_type != ECRYPTFS_PASSWORD) {
> --
> 1.7.4
>




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