@@ -189,6 +189,17 @@ struct key {
#define KEY_FLAG_KEEP 10 /* set if key should not be removed */
#define KEY_FLAG_UID_KEYRING 11 /* set if key is a user or user session keyring */
+ /*
+ * If the key is negatively instantiated, then bits 20-31 hold the error
+ * code which should be returned when someone tries to use the key
+ * (unless they allow negative keys). The error code is stored as a
+ * positive number, so it must be negated before being returned.
+ *
+ * Note that a key can go from negative to positive but not vice versa.
+ */
+#define KEY_FLAGS_REJECT_ERROR_SHIFT 20
+#define KEY_FLAGS_REJECT_ERROR_MASK 0xFFF00000
+
/* the key type and key description string
* - the desc is used to match a key against search criteria
* - it should be a printable string
@@ -213,7 +224,6 @@ struct key {
struct list_head name_link;
struct assoc_array keys;
};
- int reject_error;
};
/* This is set on a keyring to restrict the addition of a link to a key
@@ -401,6 +401,20 @@ int key_payload_reserve(struct key *key, size_t datalen)
}
EXPORT_SYMBOL(key_payload_reserve);
+static void mark_key_instantiated(struct key *key, unsigned int reject_error)
+{
+ unsigned long old, new;
+
+ do {
+ old = READ_ONCE(key->flags);
+ new = (old & ~(KEY_FLAG_NEGATIVE |
+ KEY_FLAGS_REJECT_ERROR_MASK)) |
+ KEY_FLAG_INSTANTIATED |
+ (reject_error ? KEY_FLAG_NEGATIVE : 0) |
+ (reject_error << KEY_FLAGS_REJECT_ERROR_SHIFT);
+ } while (cmpxchg_release(&key->flags, old, new) != old);
+}
+
/*
* Instantiate a key and link it into the target keyring atomically. Must be
* called with the target keyring's semaphore writelocked. The target key's
@@ -431,7 +445,7 @@ static int __key_instantiate_and_link(struct key *key,
if (ret == 0) {
/* mark the key as being instantiated */
atomic_inc(&key->user->nikeys);
- set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
+ mark_key_instantiated(key, 0);
if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
awaken = 1;
@@ -580,10 +594,8 @@ int key_reject_and_link(struct key *key,
if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
/* mark the key as being negatively instantiated */
atomic_inc(&key->user->nikeys);
- key->reject_error = -error;
- smp_wmb();
- set_bit(KEY_FLAG_NEGATIVE, &key->flags);
- set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
+ mark_key_instantiated(key, error);
+
now = current_kernel_time();
key->expiry = now.tv_sec + timeout;
key_schedule_gc(key->expiry + key_gc_delay);
@@ -753,7 +765,7 @@ static inline key_ref_t __key_update(key_ref_t key_ref,
ret = key->type->update(key, prep);
if (ret == 0)
/* updating a negative key instantiates it */
- clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
+ mark_key_instantiated(key, 0);
up_write(&key->sem);
@@ -987,7 +999,7 @@ int key_update(key_ref_t key_ref, const void *payload, size_t plen)
ret = key->type->update(key, &prep);
if (ret == 0)
/* updating a negative key instantiates it */
- clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
+ mark_key_instantiated(key, 0);
up_write(&key->sem);
@@ -1223,6 +1223,9 @@ long keyctl_reject_key(key_serial_t id, unsigned timeout, unsigned error,
error == ERESTART_RESTARTBLOCK)
return -EINVAL;
+ BUILD_BUG_ON(MAX_ERRNO > (KEY_FLAGS_REJECT_ERROR_MASK >>
+ KEY_FLAGS_REJECT_ERROR_SHIFT));
+
/* the appropriate instantiation authorisation key must have been
* assumed before calling this */
ret = -EPERM;
@@ -598,8 +598,8 @@ static int keyring_search_iterator(const void *object, void *iterator_data)
if (ctx->flags & KEYRING_SEARCH_DO_STATE_CHECK) {
/* we set a different error code if we pass a negative key */
if (kflags & (1 << KEY_FLAG_NEGATIVE)) {
- smp_rmb();
- ctx->result = ERR_PTR(key->reject_error);
+ ctx->result = ERR_PTR(-(int)(kflags >>
+ KEY_FLAGS_REJECT_ERROR_SHIFT));
kleave(" = %d [neg]", ctx->skipped_ret);
goto skipped;
}
@@ -590,15 +590,18 @@ struct key *request_key_and_link(struct key_type *type,
int wait_for_key_construction(struct key *key, bool intr)
{
int ret;
+ unsigned long flags;
ret = wait_on_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT,
intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
if (ret)
return -ERESTARTSYS;
- if (test_bit(KEY_FLAG_NEGATIVE, &key->flags)) {
- smp_rmb();
- return key->reject_error;
- }
+
+ /* Pairs with RELEASE in mark_key_instantiated() */
+ flags = smp_load_acquire(&key->flags);
+ if (flags & (1 << KEY_FLAG_NEGATIVE))
+ return -(int)(flags >> KEY_FLAGS_REJECT_ERROR_SHIFT);
+
return key_validate(key);
}
EXPORT_SYMBOL(wait_for_key_construction);