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SubjectRe: [PATCH 4/5] eCryptfs: move ecryptfs_find_auth_tok_for_sig() call before mutex_lock
Date
On Friday, March 18, 2011 04:30:50 pm Tyler Hicks wrote:
> 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.
>

Hi Tyler

i did this because i was thinking that 'tfm_mutex' is protecting
the 'auth_tok' field of the ecryptfs_parse_tag_70_packet_silly_stack
structure. Sorry, my mistake.

Thanks

Roberto


> > 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) {
>
>
>


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