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keys: Hoist locking out of __key_link_begin()

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Hoist the locking of out of __key_link_begin() and into its callers.  This
is necessary to allow the upcoming key_move() operation to correctly order
taking of the source keyring semaphore, the destination keyring semaphore
and the keyring serialisation lock.

Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
David Howells
2019-05-30 11:37:39 +01:00
parent eb0f68cb70
commit df593ee23e
4 changed files with 77 additions and 39 deletions
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80
security/keys/keyring.c
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@@ -1199,14 +1199,34 @@ static int keyring_detect_cycle(struct key *A, struct key *B)
return PTR_ERR(ctx.result) == -EAGAIN ? 0 : PTR_ERR(ctx.result);
}
/*
* Lock keyring for link.
*/
int __key_link_lock(struct key *keyring,
const struct keyring_index_key *index_key)
__acquires(&keyring->sem)
__acquires(&keyring_serialise_link_lock)
{
if (keyring->type != &key_type_keyring)
return -ENOTDIR;
down_write(&keyring->sem);
/* Serialise link/link calls to prevent parallel calls causing a cycle
* when linking two keyring in opposite orders.
*/
if (index_key->type == &key_type_keyring)
mutex_lock(&keyring_serialise_link_lock);
return 0;
}
/*
* Preallocate memory so that a key can be linked into to a keyring.
*/
int __key_link_begin(struct key *keyring,
const struct keyring_index_key *index_key,
struct assoc_array_edit **_edit)
__acquires(&keyring->sem)
__acquires(&keyring_serialise_link_lock)
{
struct assoc_array_edit *edit;
int ret;
@@ -1215,20 +1235,13 @@ int __key_link_begin(struct key *keyring,
keyring->serial, index_key->type->name, index_key->description);
BUG_ON(index_key->desc_len == 0);
BUG_ON(*_edit != NULL);
if (keyring->type != &key_type_keyring)
return -ENOTDIR;
down_write(&keyring->sem);
*_edit = NULL;
ret = -EKEYREVOKED;
if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
goto error_krsem;
/* serialise link/link calls to prevent parallel calls causing a cycle
* when linking two keyring in opposite orders */
if (index_key->type == &key_type_keyring)
mutex_lock(&keyring_serialise_link_lock);
goto error;
/* Create an edit script that will insert/replace the key in the
* keyring tree.
@@ -1239,7 +1252,7 @@ int __key_link_begin(struct key *keyring,
NULL);
if (IS_ERR(edit)) {
ret = PTR_ERR(edit);
goto error_sem;
goto error;
}
/* If we're not replacing a link in-place then we're going to need some
@@ -1258,11 +1271,7 @@ int __key_link_begin(struct key *keyring,
error_cancel:
assoc_array_cancel_edit(edit);
error_sem:
if (index_key->type == &key_type_keyring)
mutex_unlock(&keyring_serialise_link_lock);
error_krsem:
up_write(&keyring->sem);
error:
kleave(" = %d", ret);
return ret;
}
@@ -1312,9 +1321,6 @@ void __key_link_end(struct key *keyring,
BUG_ON(index_key->type == NULL);
kenter("%d,%s,", keyring->serial, index_key->type->name);
if (index_key->type == &key_type_keyring)
mutex_unlock(&keyring_serialise_link_lock);
if (edit) {
if (!edit->dead_leaf) {
key_payload_reserve(keyring,
@@ -1323,6 +1329,9 @@ void __key_link_end(struct key *keyring,
assoc_array_cancel_edit(edit);
}
up_write(&keyring->sem);
if (index_key->type == &key_type_keyring)
mutex_unlock(&keyring_serialise_link_lock);
}
/*
@@ -1358,7 +1367,7 @@ static int __key_link_check_restriction(struct key *keyring, struct key *key)
*/
int key_link(struct key *keyring, struct key *key)
{
struct assoc_array_edit *edit;
struct assoc_array_edit *edit = NULL;
int ret;
kenter("{%d,%d}", keyring->serial, refcount_read(&keyring->usage));
@@ -1366,17 +1375,24 @@ int key_link(struct key *keyring, struct key *key)
key_check(keyring);
key_check(key);
ret = __key_link_begin(keyring, &key->index_key, &edit);
if (ret == 0) {
kdebug("begun {%d,%d}", keyring->serial, refcount_read(&keyring->usage));
ret = __key_link_check_restriction(keyring, key);
if (ret == 0)
ret = __key_link_check_live_key(keyring, key);
if (ret == 0)
__key_link(key, &edit);
__key_link_end(keyring, &key->index_key, edit);
}
ret = __key_link_lock(keyring, &key->index_key);
if (ret < 0)
goto error;
ret = __key_link_begin(keyring, &key->index_key, &edit);
if (ret < 0)
goto error_end;
kdebug("begun {%d,%d}", keyring->serial, refcount_read(&keyring->usage));
ret = __key_link_check_restriction(keyring, key);
if (ret == 0)
ret = __key_link_check_live_key(keyring, key);
if (ret == 0)
__key_link(key, &edit);
error_end:
__key_link_end(keyring, &key->index_key, edit);
error:
kleave(" = %d {%d,%d}", ret, keyring->serial, refcount_read(&keyring->usage));
return ret;
}