[PATCH 2/6] Keys: Discard the contents of a key on revocation [try #3]

From: David Howells
Date: Tue Jun 20 2006 - 13:37:10 EST


From: David Howells <dhowells@xxxxxxxxxx>

The attached patch causes the keys linked to a keyring to be unlinked from it
when revoked and it causes the data attached to a user-defined key to be
discarded when revoked.

This frees up most of the quota a key occupied at that point, rather than
waiting for the key to actually be destroyed.

Signed-Off-By: David Howells <dhowells@xxxxxxxxxx>
---

include/keys/user-type.h | 1 +
security/keys/keyring.c | 21 +++++++++++++++++++++
security/keys/user_defined.c | 25 ++++++++++++++++++++++++-
3 files changed, 46 insertions(+), 1 deletions(-)

diff --git a/include/keys/user-type.h b/include/keys/user-type.h
index a3dae18..c37c342 100644
--- a/include/keys/user-type.h
+++ b/include/keys/user-type.h
@@ -37,6 +37,7 @@ extern struct key_type key_type_user;
extern int user_instantiate(struct key *key, const void *data, size_t datalen);
extern int user_update(struct key *key, const void *data, size_t datalen);
extern int user_match(const struct key *key, const void *criterion);
+extern void user_revoke(struct key *key);
extern void user_destroy(struct key *key);
extern void user_describe(const struct key *user, struct seq_file *m);
extern long user_read(const struct key *key,
diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index 6c282bd..e8d02ac 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -49,6 +49,7 @@ static inline unsigned keyring_hash(cons
static int keyring_instantiate(struct key *keyring,
const void *data, size_t datalen);
static int keyring_match(const struct key *keyring, const void *criterion);
+static void keyring_revoke(struct key *keyring);
static void keyring_destroy(struct key *keyring);
static void keyring_describe(const struct key *keyring, struct seq_file *m);
static long keyring_read(const struct key *keyring,
@@ -59,6 +60,7 @@ struct key_type key_type_keyring = {
.def_datalen = sizeof(struct keyring_list),
.instantiate = keyring_instantiate,
.match = keyring_match,
+ .revoke = keyring_revoke,
.destroy = keyring_destroy,
.describe = keyring_describe,
.read = keyring_read,
@@ -953,3 +955,22 @@ int keyring_clear(struct key *keyring)
} /* end keyring_clear() */

EXPORT_SYMBOL(keyring_clear);
+
+/*****************************************************************************/
+/*
+ * dispose of the links from a revoked keyring
+ * - called with the key sem write-locked
+ */
+static void keyring_revoke(struct key *keyring)
+{
+ struct keyring_list *klist = keyring->payload.subscriptions;
+
+ /* adjust the quota */
+ key_payload_reserve(keyring, 0);
+
+ if (klist) {
+ rcu_assign_pointer(keyring->payload.subscriptions, NULL);
+ call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
+ }
+
+} /* end keyring_revoke() */
diff --git a/security/keys/user_defined.c b/security/keys/user_defined.c
index 8e71895..5bbfdeb 100644
--- a/security/keys/user_defined.c
+++ b/security/keys/user_defined.c
@@ -28,6 +28,7 @@ struct key_type key_type_user = {
.instantiate = user_instantiate,
.update = user_update,
.match = user_match,
+ .revoke = user_revoke,
.destroy = user_destroy,
.describe = user_describe,
.read = user_read,
@@ -67,6 +68,7 @@ error:
return ret;

} /* end user_instantiate() */
+
EXPORT_SYMBOL_GPL(user_instantiate);

/*****************************************************************************/
@@ -141,7 +143,28 @@ EXPORT_SYMBOL_GPL(user_match);

/*****************************************************************************/
/*
- * dispose of the data dangling from the corpse of a user
+ * dispose of the links from a revoked keyring
+ * - called with the key sem write-locked
+ */
+void user_revoke(struct key *key)
+{
+ struct user_key_payload *upayload = key->payload.data;
+
+ /* clear the quota */
+ key_payload_reserve(key, 0);
+
+ if (upayload) {
+ rcu_assign_pointer(key->payload.data, NULL);
+ call_rcu(&upayload->rcu, user_update_rcu_disposal);
+ }
+
+} /* end user_revoke() */
+
+EXPORT_SYMBOL(user_revoke);
+
+/*****************************************************************************/
+/*
+ * dispose of the data dangling from the corpse of a user key
*/
void user_destroy(struct key *key)
{

-
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