futex: Fix a race condition between REQUEUE_PI and task death

[pandora-kernel.git] / kernel / futex.c

diff --git a/kernel/futex.c b/kernel/futex.c
index f31f190..7481595 100644 (file)
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -484,8 +484,14 @@ static struct futex_pi_state * alloc_pi_state(void)
        return pi_state;
 }
 
+/*
+ * Must be called with the hb lock held.
+ */
 static void free_pi_state(struct futex_pi_state *pi_state)
 {
+       if (!pi_state)
+               return;
+
        if (!atomic_dec_and_test(&pi_state->refcount))
                return;
 
@@ -1399,15 +1405,6 @@ static int futex_requeue(u32 __user *uaddr1, unsigned int flags,
        }
 
 retry:
-       if (pi_state != NULL) {
-               /*
-                * We will have to lookup the pi_state again, so free this one
-                * to keep the accounting correct.
-                */
-               free_pi_state(pi_state);
-               pi_state = NULL;
-       }
-
        ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, VERIFY_READ);
        if (unlikely(ret != 0))
                goto out;
@@ -1495,6 +1492,8 @@ retry_private:
                case 0:
                        break;
                case -EFAULT:
+                       free_pi_state(pi_state);
+                       pi_state = NULL;
                        double_unlock_hb(hb1, hb2);
                        put_futex_key(&key2);
                        put_futex_key(&key1);
@@ -1504,6 +1503,8 @@ retry_private:
                        goto out;
                case -EAGAIN:
                        /* The owner was exiting, try again. */
+                       free_pi_state(pi_state);
+                       pi_state = NULL;
                        double_unlock_hb(hb1, hb2);
                        put_futex_key(&key2);
                        put_futex_key(&key1);
@@ -1580,6 +1581,7 @@ retry_private:
        }
 
 out_unlock:
+       free_pi_state(pi_state);
        double_unlock_hb(hb1, hb2);
 
        /*
@@ -1596,8 +1598,6 @@ out_put_keys:
 out_put_key1:
        put_futex_key(&key1);
 out:
-       if (pi_state != NULL)
-               free_pi_state(pi_state);
        return ret ? ret : task_count;
 }