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authorIngo Molnar2006-07-29 05:16:20 +0200
committerLinus Torvalds2006-07-28 21:02:00 -0700
commit627371d73cdd04ed23fe098755b4f855138ad9e0 (patch)
tree2371684c61f91c39f562a6570784a1bae50f53a5 /kernel
parentc97d20a6c51067a38f53680d9609b4cf2867d077 (diff)
[PATCH] pi-futex: robust-futex exit crash fix
Fix pi_state->list handling bugs: list handling mishap, locking error. Plus add more debug checks and fix a few style issues i noticed while debugging this. (reported by Ulrich Drepper and Jakub Jelinek.) Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/futex.c32
1 files changed, 24 insertions, 8 deletions
diff --git a/kernel/futex.c b/kernel/futex.c
index cf0c8e21d1ab..f59003b1d8f9 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -415,15 +415,15 @@ out_unlock:
*/
void exit_pi_state_list(struct task_struct *curr)
{
- struct futex_hash_bucket *hb;
struct list_head *next, *head = &curr->pi_state_list;
struct futex_pi_state *pi_state;
+ struct futex_hash_bucket *hb;
union futex_key key;
/*
* We are a ZOMBIE and nobody can enqueue itself on
* pi_state_list anymore, but we have to be careful
- * versus waiters unqueueing themselfs
+ * versus waiters unqueueing themselves:
*/
spin_lock_irq(&curr->pi_lock);
while (!list_empty(head)) {
@@ -431,21 +431,24 @@ void exit_pi_state_list(struct task_struct *curr)
next = head->next;
pi_state = list_entry(next, struct futex_pi_state, list);
key = pi_state->key;
+ hb = hash_futex(&key);
spin_unlock_irq(&curr->pi_lock);
- hb = hash_futex(&key);
spin_lock(&hb->lock);
spin_lock_irq(&curr->pi_lock);
+ /*
+ * We dropped the pi-lock, so re-check whether this
+ * task still owns the PI-state:
+ */
if (head->next != next) {
spin_unlock(&hb->lock);
continue;
}
- list_del_init(&pi_state->list);
-
WARN_ON(pi_state->owner != curr);
-
+ WARN_ON(list_empty(&pi_state->list));
+ list_del_init(&pi_state->list);
pi_state->owner = NULL;
spin_unlock_irq(&curr->pi_lock);
@@ -470,7 +473,7 @@ lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, struct futex_q *me)
head = &hb->chain;
list_for_each_entry_safe(this, next, head, list) {
- if (match_futex (&this->key, &me->key)) {
+ if (match_futex(&this->key, &me->key)) {
/*
* Another waiter already exists - bump up
* the refcount and return its pi_state:
@@ -482,6 +485,8 @@ lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, struct futex_q *me)
if (unlikely(!pi_state))
return -EINVAL;
+ WARN_ON(!atomic_read(&pi_state->refcount));
+
atomic_inc(&pi_state->refcount);
me->pi_state = pi_state;
@@ -510,6 +515,7 @@ lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, struct futex_q *me)
pi_state->key = me->key;
spin_lock_irq(&p->pi_lock);
+ WARN_ON(!list_empty(&pi_state->list));
list_add(&pi_state->list, &p->pi_state_list);
pi_state->owner = p;
spin_unlock_irq(&p->pi_lock);
@@ -584,9 +590,17 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this)
if (curval != uval)
return -EINVAL;
- list_del_init(&pi_state->owner->pi_state_list);
+ spin_lock_irq(&pi_state->owner->pi_lock);
+ WARN_ON(list_empty(&pi_state->list));
+ list_del_init(&pi_state->list);
+ spin_unlock_irq(&pi_state->owner->pi_lock);
+
+ spin_lock_irq(&new_owner->pi_lock);
+ WARN_ON(!list_empty(&pi_state->list));
list_add(&pi_state->list, &new_owner->pi_state_list);
pi_state->owner = new_owner;
+ spin_unlock_irq(&new_owner->pi_lock);
+
rt_mutex_unlock(&pi_state->pi_mutex);
return 0;
@@ -1236,6 +1250,7 @@ static int do_futex_lock_pi(u32 __user *uaddr, int detect, int trylock,
/* Owner died? */
if (q.pi_state->owner != NULL) {
spin_lock_irq(&q.pi_state->owner->pi_lock);
+ WARN_ON(list_empty(&q.pi_state->list));
list_del_init(&q.pi_state->list);
spin_unlock_irq(&q.pi_state->owner->pi_lock);
} else
@@ -1244,6 +1259,7 @@ static int do_futex_lock_pi(u32 __user *uaddr, int detect, int trylock,
q.pi_state->owner = current;
spin_lock_irq(&current->pi_lock);
+ WARN_ON(!list_empty(&q.pi_state->list));
list_add(&q.pi_state->list, &current->pi_state_list);
spin_unlock_irq(&current->pi_lock);