KEYS: Do preallocation for __key_link()
Do preallocation for __key_link() so that the various callers in request_key.c
can deal with any errors from this source before attempting to construct a key.
This allows them to assume that the actual linkage step is guaranteed to be
successful.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index 3f425a6..ef03a82a0 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -660,20 +660,6 @@
} /* end keyring_detect_cycle() */
-/*****************************************************************************/
-/*
- * dispose of a keyring list after the RCU grace period
- */
-static void keyring_link_rcu_disposal(struct rcu_head *rcu)
-{
- struct keyring_list *klist =
- container_of(rcu, struct keyring_list, rcu);
-
- kfree(klist);
-
-} /* end keyring_link_rcu_disposal() */
-
-/*****************************************************************************/
/*
* dispose of a keyring list after the RCU grace period, freeing the unlinked
* key
@@ -683,56 +669,51 @@
struct keyring_list *klist =
container_of(rcu, struct keyring_list, rcu);
- key_put(klist->keys[klist->delkey]);
+ if (klist->delkey != USHORT_MAX)
+ key_put(klist->keys[klist->delkey]);
kfree(klist);
+}
-} /* end keyring_unlink_rcu_disposal() */
-
-/*****************************************************************************/
/*
- * link a key into to a keyring
- * - must be called with the keyring's semaphore write-locked
- * - discard already extant link to matching key if there is one
+ * preallocate memory so that a key can be linked into to a keyring
*/
-int __key_link(struct key *keyring, struct key *key)
+int __key_link_begin(struct key *keyring, const struct key_type *type,
+ const char *description,
+ struct keyring_list **_prealloc)
+ __acquires(&keyring->sem)
{
struct keyring_list *klist, *nklist;
unsigned max;
size_t size;
int loop, ret;
+ kenter("%d,%s,%s,", key_serial(keyring), type->name, description);
+
+ if (keyring->type != &key_type_keyring)
+ return -ENOTDIR;
+
+ down_write(&keyring->sem);
+
ret = -EKEYREVOKED;
if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
- goto error;
+ goto error_krsem;
- ret = -ENOTDIR;
- if (keyring->type != &key_type_keyring)
- goto error;
-
- /* do some special keyring->keyring link checks */
- if (key->type == &key_type_keyring) {
- /* serialise link/link calls to prevent parallel calls causing
- * a cycle when applied to two keyring in opposite orders */
+ /* serialise link/link calls to prevent parallel calls causing a cycle
+ * when linking two keyring in opposite orders */
+ if (type == &key_type_keyring)
down_write(&keyring_serialise_link_sem);
- /* check that we aren't going to create a cycle adding one
- * keyring to another */
- ret = keyring_detect_cycle(keyring, key);
- if (ret < 0)
- goto error2;
- }
+ klist = rcu_dereference_locked_keyring(keyring);
/* see if there's a matching key we can displace */
- klist = rcu_dereference_locked_keyring(keyring);
if (klist && klist->nkeys > 0) {
- struct key_type *type = key->type;
-
for (loop = klist->nkeys - 1; loop >= 0; loop--) {
if (klist->keys[loop]->type == type &&
strcmp(klist->keys[loop]->description,
- key->description) == 0
+ description) == 0
) {
- /* found a match - replace with new key */
+ /* found a match - we'll replace this one with
+ * the new key */
size = sizeof(struct key *) * klist->maxkeys;
size += sizeof(*klist);
BUG_ON(size > PAGE_SIZE);
@@ -740,22 +721,10 @@
ret = -ENOMEM;
nklist = kmemdup(klist, size, GFP_KERNEL);
if (!nklist)
- goto error2;
+ goto error_sem;
- /* replace matched key */
- atomic_inc(&key->usage);
- nklist->keys[loop] = key;
-
- rcu_assign_pointer(
- keyring->payload.subscriptions,
- nklist);
-
- /* dispose of the old keyring list and the
- * displaced key */
- klist->delkey = loop;
- call_rcu(&klist->rcu,
- keyring_unlink_rcu_disposal);
-
+ /* note replacement slot */
+ klist->delkey = nklist->delkey = loop;
goto done;
}
}
@@ -765,16 +734,11 @@
ret = key_payload_reserve(keyring,
keyring->datalen + KEYQUOTA_LINK_BYTES);
if (ret < 0)
- goto error2;
+ goto error_sem;
if (klist && klist->nkeys < klist->maxkeys) {
- /* there's sufficient slack space to add directly */
- atomic_inc(&key->usage);
-
- klist->keys[klist->nkeys] = key;
- smp_wmb();
- klist->nkeys++;
- smp_wmb();
+ /* there's sufficient slack space to append directly */
+ nklist = NULL;
} else {
/* grow the key list */
max = 4;
@@ -782,71 +746,155 @@
max += klist->maxkeys;
ret = -ENFILE;
- if (max > 65535)
- goto error3;
+ if (max > USHORT_MAX - 1)
+ goto error_quota;
size = sizeof(*klist) + sizeof(struct key *) * max;
if (size > PAGE_SIZE)
- goto error3;
+ goto error_quota;
ret = -ENOMEM;
nklist = kmalloc(size, GFP_KERNEL);
if (!nklist)
- goto error3;
- nklist->maxkeys = max;
- nklist->nkeys = 0;
+ goto error_quota;
+ nklist->maxkeys = max;
if (klist) {
- nklist->nkeys = klist->nkeys;
- memcpy(nklist->keys,
- klist->keys,
+ memcpy(nklist->keys, klist->keys,
sizeof(struct key *) * klist->nkeys);
+ nklist->delkey = klist->nkeys;
+ nklist->nkeys = klist->nkeys + 1;
+ klist->delkey = USHORT_MAX;
+ } else {
+ nklist->nkeys = 1;
+ nklist->delkey = 0;
}
/* add the key into the new space */
- atomic_inc(&key->usage);
- nklist->keys[nklist->nkeys++] = key;
-
- rcu_assign_pointer(keyring->payload.subscriptions, nklist);
-
- /* dispose of the old keyring list */
- if (klist)
- call_rcu(&klist->rcu, keyring_link_rcu_disposal);
+ nklist->keys[nklist->delkey] = NULL;
}
done:
- ret = 0;
-error2:
- if (key->type == &key_type_keyring)
- up_write(&keyring_serialise_link_sem);
-error:
- return ret;
+ *_prealloc = nklist;
+ kleave(" = 0");
+ return 0;
-error3:
+error_quota:
/* undo the quota changes */
key_payload_reserve(keyring,
keyring->datalen - KEYQUOTA_LINK_BYTES);
- goto error2;
+error_sem:
+ if (type == &key_type_keyring)
+ up_write(&keyring_serialise_link_sem);
+error_krsem:
+ up_write(&keyring->sem);
+ kleave(" = %d", ret);
+ return ret;
+}
-} /* end __key_link() */
+/*
+ * check already instantiated keys aren't going to be a problem
+ * - the caller must have called __key_link_begin()
+ * - don't need to call this for keys that were created since __key_link_begin()
+ * was called
+ */
+int __key_link_check_live_key(struct key *keyring, struct key *key)
+{
+ if (key->type == &key_type_keyring)
+ /* check that we aren't going to create a cycle by linking one
+ * keyring to another */
+ return keyring_detect_cycle(keyring, key);
+ return 0;
+}
-/*****************************************************************************/
+/*
+ * link a key into to a keyring
+ * - must be called with __key_link_begin() having being called
+ * - discard already extant link to matching key if there is one
+ */
+void __key_link(struct key *keyring, struct key *key,
+ struct keyring_list **_prealloc)
+{
+ struct keyring_list *klist, *nklist;
+
+ nklist = *_prealloc;
+ *_prealloc = NULL;
+
+ kenter("%d,%d,%p", keyring->serial, key->serial, nklist);
+
+ klist = rcu_dereference_protected(keyring->payload.subscriptions,
+ rwsem_is_locked(&keyring->sem));
+
+ atomic_inc(&key->usage);
+
+ /* there's a matching key we can displace or an empty slot in a newly
+ * allocated list we can fill */
+ if (nklist) {
+ kdebug("replace %hu/%hu/%hu",
+ nklist->delkey, nklist->nkeys, nklist->maxkeys);
+
+ nklist->keys[nklist->delkey] = key;
+
+ rcu_assign_pointer(keyring->payload.subscriptions, nklist);
+
+ /* dispose of the old keyring list and, if there was one, the
+ * displaced key */
+ if (klist) {
+ kdebug("dispose %hu/%hu/%hu",
+ klist->delkey, klist->nkeys, klist->maxkeys);
+ call_rcu(&klist->rcu, keyring_unlink_rcu_disposal);
+ }
+ } else {
+ /* there's sufficient slack space to append directly */
+ klist->keys[klist->nkeys] = key;
+ smp_wmb();
+ klist->nkeys++;
+ }
+}
+
+/*
+ * finish linking a key into to a keyring
+ * - must be called with __key_link_begin() having being called
+ */
+void __key_link_end(struct key *keyring, struct key_type *type,
+ struct keyring_list *prealloc)
+ __releases(&keyring->sem)
+{
+ BUG_ON(type == NULL);
+ BUG_ON(type->name == NULL);
+ kenter("%d,%s,%p", keyring->serial, type->name, prealloc);
+
+ if (type == &key_type_keyring)
+ up_write(&keyring_serialise_link_sem);
+
+ if (prealloc) {
+ kfree(prealloc);
+ key_payload_reserve(keyring,
+ keyring->datalen - KEYQUOTA_LINK_BYTES);
+ }
+ up_write(&keyring->sem);
+}
+
/*
* link a key to a keyring
*/
int key_link(struct key *keyring, struct key *key)
{
+ struct keyring_list *prealloc;
int ret;
key_check(keyring);
key_check(key);
- down_write(&keyring->sem);
- ret = __key_link(keyring, key);
- up_write(&keyring->sem);
+ ret = __key_link_begin(keyring, key->type, key->description, &prealloc);
+ if (ret == 0) {
+ ret = __key_link_check_live_key(keyring, key);
+ if (ret == 0)
+ __key_link(keyring, key, &prealloc);
+ __key_link_end(keyring, key->type, prealloc);
+ }
return ret;
-
-} /* end key_link() */
+}
EXPORT_SYMBOL(key_link);