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>
This commit is contained in:
David Howells
committed by
James Morris
James Morris
parent
043b4d40f5
commit
f70e2e0619
@@ -660,20 +660,6 @@ cycle_detected:
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} /* end keyring_detect_cycle() */
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/*****************************************************************************/
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/*
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* dispose of a keyring list after the RCU grace period
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*/
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static void keyring_link_rcu_disposal(struct rcu_head *rcu)
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{
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struct keyring_list *klist =
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container_of(rcu, struct keyring_list, rcu);
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kfree(klist);
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} /* end keyring_link_rcu_disposal() */
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/*****************************************************************************/
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/*
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* dispose of a keyring list after the RCU grace period, freeing the unlinked
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* key
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@@ -683,56 +669,51 @@ static void keyring_unlink_rcu_disposal(struct rcu_head *rcu)
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struct keyring_list *klist =
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container_of(rcu, struct keyring_list, rcu);
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key_put(klist->keys[klist->delkey]);
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if (klist->delkey != USHORT_MAX)
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key_put(klist->keys[klist->delkey]);
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kfree(klist);
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}
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} /* end keyring_unlink_rcu_disposal() */
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/*****************************************************************************/
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/*
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* link a key into to a keyring
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* - must be called with the keyring's semaphore write-locked
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* - discard already extant link to matching key if there is one
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* preallocate memory so that a key can be linked into to a keyring
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*/
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int __key_link(struct key *keyring, struct key *key)
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int __key_link_begin(struct key *keyring, const struct key_type *type,
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const char *description,
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struct keyring_list **_prealloc)
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__acquires(&keyring->sem)
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{
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struct keyring_list *klist, *nklist;
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unsigned max;
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size_t size;
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int loop, ret;
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kenter("%d,%s,%s,", key_serial(keyring), type->name, description);
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if (keyring->type != &key_type_keyring)
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return -ENOTDIR;
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down_write(&keyring->sem);
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ret = -EKEYREVOKED;
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if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
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goto error;
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goto error_krsem;
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ret = -ENOTDIR;
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if (keyring->type != &key_type_keyring)
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goto error;
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/* do some special keyring->keyring link checks */
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if (key->type == &key_type_keyring) {
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/* serialise link/link calls to prevent parallel calls causing
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* a cycle when applied to two keyring in opposite orders */
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/* serialise link/link calls to prevent parallel calls causing a cycle
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* when linking two keyring in opposite orders */
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if (type == &key_type_keyring)
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down_write(&keyring_serialise_link_sem);
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/* check that we aren't going to create a cycle adding one
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* keyring to another */
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ret = keyring_detect_cycle(keyring, key);
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if (ret < 0)
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goto error2;
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}
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klist = rcu_dereference_locked_keyring(keyring);
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/* see if there's a matching key we can displace */
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klist = rcu_dereference_locked_keyring(keyring);
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if (klist && klist->nkeys > 0) {
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struct key_type *type = key->type;
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for (loop = klist->nkeys - 1; loop >= 0; loop--) {
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if (klist->keys[loop]->type == type &&
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strcmp(klist->keys[loop]->description,
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key->description) == 0
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description) == 0
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) {
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/* found a match - replace with new key */
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/* found a match - we'll replace this one with
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* the new key */
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size = sizeof(struct key *) * klist->maxkeys;
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size += sizeof(*klist);
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BUG_ON(size > PAGE_SIZE);
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@@ -740,22 +721,10 @@ int __key_link(struct key *keyring, struct key *key)
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ret = -ENOMEM;
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nklist = kmemdup(klist, size, GFP_KERNEL);
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if (!nklist)
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goto error2;
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/* replace matched key */
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atomic_inc(&key->usage);
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nklist->keys[loop] = key;
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rcu_assign_pointer(
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keyring->payload.subscriptions,
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nklist);
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/* dispose of the old keyring list and the
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* displaced key */
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klist->delkey = loop;
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call_rcu(&klist->rcu,
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keyring_unlink_rcu_disposal);
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goto error_sem;
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/* note replacement slot */
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klist->delkey = nklist->delkey = loop;
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goto done;
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}
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}
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@@ -765,16 +734,11 @@ int __key_link(struct key *keyring, struct key *key)
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ret = key_payload_reserve(keyring,
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keyring->datalen + KEYQUOTA_LINK_BYTES);
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if (ret < 0)
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goto error2;
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goto error_sem;
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if (klist && klist->nkeys < klist->maxkeys) {
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/* there's sufficient slack space to add directly */
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atomic_inc(&key->usage);
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klist->keys[klist->nkeys] = key;
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smp_wmb();
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klist->nkeys++;
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smp_wmb();
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/* there's sufficient slack space to append directly */
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nklist = NULL;
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} else {
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/* grow the key list */
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max = 4;
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@@ -782,71 +746,155 @@ int __key_link(struct key *keyring, struct key *key)
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max += klist->maxkeys;
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ret = -ENFILE;
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if (max > 65535)
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goto error3;
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if (max > USHORT_MAX - 1)
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goto error_quota;
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size = sizeof(*klist) + sizeof(struct key *) * max;
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if (size > PAGE_SIZE)
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goto error3;
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goto error_quota;
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ret = -ENOMEM;
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nklist = kmalloc(size, GFP_KERNEL);
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if (!nklist)
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goto error3;
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nklist->maxkeys = max;
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nklist->nkeys = 0;
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goto error_quota;
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nklist->maxkeys = max;
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if (klist) {
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nklist->nkeys = klist->nkeys;
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memcpy(nklist->keys,
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klist->keys,
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memcpy(nklist->keys, klist->keys,
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sizeof(struct key *) * klist->nkeys);
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nklist->delkey = klist->nkeys;
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nklist->nkeys = klist->nkeys + 1;
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klist->delkey = USHORT_MAX;
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} else {
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nklist->nkeys = 1;
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nklist->delkey = 0;
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}
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/* add the key into the new space */
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atomic_inc(&key->usage);
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nklist->keys[nklist->nkeys++] = key;
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rcu_assign_pointer(keyring->payload.subscriptions, nklist);
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/* dispose of the old keyring list */
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if (klist)
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call_rcu(&klist->rcu, keyring_link_rcu_disposal);
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nklist->keys[nklist->delkey] = NULL;
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}
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done:
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ret = 0;
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error2:
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if (key->type == &key_type_keyring)
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up_write(&keyring_serialise_link_sem);
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error:
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return ret;
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*_prealloc = nklist;
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kleave(" = 0");
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return 0;
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error3:
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error_quota:
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/* undo the quota changes */
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key_payload_reserve(keyring,
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keyring->datalen - KEYQUOTA_LINK_BYTES);
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goto error2;
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error_sem:
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if (type == &key_type_keyring)
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up_write(&keyring_serialise_link_sem);
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error_krsem:
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up_write(&keyring->sem);
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kleave(" = %d", ret);
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return ret;
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}
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} /* end __key_link() */
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/*
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* check already instantiated keys aren't going to be a problem
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* - the caller must have called __key_link_begin()
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* - don't need to call this for keys that were created since __key_link_begin()
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* was called
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*/
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int __key_link_check_live_key(struct key *keyring, struct key *key)
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{
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if (key->type == &key_type_keyring)
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/* check that we aren't going to create a cycle by linking one
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* keyring to another */
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return keyring_detect_cycle(keyring, key);
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return 0;
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}
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/*
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* link a key into to a keyring
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* - must be called with __key_link_begin() having being called
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* - discard already extant link to matching key if there is one
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*/
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void __key_link(struct key *keyring, struct key *key,
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struct keyring_list **_prealloc)
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{
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struct keyring_list *klist, *nklist;
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nklist = *_prealloc;
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*_prealloc = NULL;
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kenter("%d,%d,%p", keyring->serial, key->serial, nklist);
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klist = rcu_dereference_protected(keyring->payload.subscriptions,
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rwsem_is_locked(&keyring->sem));
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atomic_inc(&key->usage);
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/* there's a matching key we can displace or an empty slot in a newly
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* allocated list we can fill */
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if (nklist) {
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kdebug("replace %hu/%hu/%hu",
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nklist->delkey, nklist->nkeys, nklist->maxkeys);
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nklist->keys[nklist->delkey] = key;
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rcu_assign_pointer(keyring->payload.subscriptions, nklist);
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/* dispose of the old keyring list and, if there was one, the
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* displaced key */
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if (klist) {
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kdebug("dispose %hu/%hu/%hu",
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klist->delkey, klist->nkeys, klist->maxkeys);
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call_rcu(&klist->rcu, keyring_unlink_rcu_disposal);
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}
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} else {
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/* there's sufficient slack space to append directly */
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klist->keys[klist->nkeys] = key;
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smp_wmb();
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klist->nkeys++;
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}
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}
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/*
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* finish linking a key into to a keyring
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* - must be called with __key_link_begin() having being called
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*/
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void __key_link_end(struct key *keyring, struct key_type *type,
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struct keyring_list *prealloc)
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__releases(&keyring->sem)
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{
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BUG_ON(type == NULL);
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BUG_ON(type->name == NULL);
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kenter("%d,%s,%p", keyring->serial, type->name, prealloc);
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if (type == &key_type_keyring)
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up_write(&keyring_serialise_link_sem);
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if (prealloc) {
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kfree(prealloc);
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key_payload_reserve(keyring,
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keyring->datalen - KEYQUOTA_LINK_BYTES);
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}
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up_write(&keyring->sem);
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}
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/*****************************************************************************/
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/*
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* link a key to a keyring
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*/
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int key_link(struct key *keyring, struct key *key)
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{
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struct keyring_list *prealloc;
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int ret;
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key_check(keyring);
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key_check(key);
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down_write(&keyring->sem);
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ret = __key_link(keyring, key);
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up_write(&keyring->sem);
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ret = __key_link_begin(keyring, key->type, key->description, &prealloc);
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if (ret == 0) {
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ret = __key_link_check_live_key(keyring, key);
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if (ret == 0)
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__key_link(keyring, key, &prealloc);
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__key_link_end(keyring, key->type, prealloc);
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}
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return ret;
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} /* end key_link() */
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}
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EXPORT_SYMBOL(key_link);
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