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-rw-r--r--kernel/futex.c59
1 files changed, 39 insertions, 20 deletions
diff --git a/kernel/futex.c b/kernel/futex.c
index 3717e7b..19eb089 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -716,7 +716,7 @@ static int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb,
struct futex_pi_state **ps,
struct task_struct *task, int set_waiters)
{
- int lock_taken, ret, ownerdied = 0;
+ int lock_taken, ret, force_take = 0;
u32 uval, newval, curval, vpid = task_pid_vnr(task);
retry:
@@ -755,17 +755,15 @@ retry:
newval = curval | FUTEX_WAITERS;
/*
- * There are two cases, where a futex might have no owner (the
- * owner TID is 0): OWNER_DIED. We take over the futex in this
- * case. We also do an unconditional take over, when the owner
- * of the futex died.
- *
- * This is safe as we are protected by the hash bucket lock !
+ * Should we force take the futex? See below.
*/
- if (unlikely(ownerdied || !(curval & FUTEX_TID_MASK))) {
- /* Keep the OWNER_DIED bit */
+ if (unlikely(force_take)) {
+ /*
+ * Keep the OWNER_DIED and the WAITERS bit and set the
+ * new TID value.
+ */
newval = (curval & ~FUTEX_TID_MASK) | vpid;
- ownerdied = 0;
+ force_take = 0;
lock_taken = 1;
}
@@ -775,7 +773,7 @@ retry:
goto retry;
/*
- * We took the lock due to owner died take over.
+ * We took the lock due to forced take over.
*/
if (unlikely(lock_taken))
return 1;
@@ -790,20 +788,25 @@ retry:
switch (ret) {
case -ESRCH:
/*
- * No owner found for this futex. Check if the
- * OWNER_DIED bit is set to figure out whether
- * this is a robust futex or not.
+ * We failed to find an owner for this
+ * futex. So we have no pi_state to block
+ * on. This can happen in two cases:
+ *
+ * 1) The owner died
+ * 2) A stale FUTEX_WAITERS bit
+ *
+ * Re-read the futex value.
*/
if (get_futex_value_locked(&curval, uaddr))
return -EFAULT;
/*
- * We simply start over in case of a robust
- * futex. The code above will take the futex
- * and return happy.
+ * If the owner died or we have a stale
+ * WAITERS bit the owner TID in the user space
+ * futex is 0.
*/
- if (curval & FUTEX_OWNER_DIED) {
- ownerdied = 1;
+ if (!(curval & FUTEX_TID_MASK)) {
+ force_take = 1;
goto retry;
}
default:
@@ -840,6 +843,9 @@ static void wake_futex(struct futex_q *q)
{
struct task_struct *p = q->task;
+ if (WARN(q->pi_state || q->rt_waiter, "refusing to wake PI futex\n"))
+ return;
+
/*
* We set q->lock_ptr = NULL _before_ we wake up the task. If
* a non-futex wake up happens on another CPU then the task
@@ -1075,6 +1081,10 @@ retry_private:
plist_for_each_entry_safe(this, next, head, list) {
if (match_futex (&this->key, &key1)) {
+ if (this->pi_state || this->rt_waiter) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
wake_futex(this);
if (++ret >= nr_wake)
break;
@@ -1087,6 +1097,10 @@ retry_private:
op_ret = 0;
plist_for_each_entry_safe(this, next, head, list) {
if (match_futex (&this->key, &key2)) {
+ if (this->pi_state || this->rt_waiter) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
wake_futex(this);
if (++op_ret >= nr_wake2)
break;
@@ -1095,6 +1109,7 @@ retry_private:
ret += op_ret;
}
+out_unlock:
double_unlock_hb(hb1, hb2);
out_put_keys:
put_futex_key(&key2);
@@ -1384,9 +1399,13 @@ retry_private:
/*
* FUTEX_WAIT_REQEUE_PI and FUTEX_CMP_REQUEUE_PI should always
* be paired with each other and no other futex ops.
+ *
+ * We should never be requeueing a futex_q with a pi_state,
+ * which is awaiting a futex_unlock_pi().
*/
if ((requeue_pi && !this->rt_waiter) ||
- (!requeue_pi && this->rt_waiter)) {
+ (!requeue_pi && this->rt_waiter) ||
+ this->pi_state) {
ret = -EINVAL;
break;
}
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