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Subject[patch 12/31] futex: PI state locking fix
-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Ingo Molnar <mingo@elte.hu>

Testing of -rt by IBM uncovered a locking bug in wake_futex_pi(): the PI
state needs to be locked before we access it.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Chuck Ebbert <cebbert@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
kernel/futex.c | 2 ++
1 file changed, 2 insertions(+)
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -565,6 +565,7 @@ static int wake_futex_pi(u32 __user *uad
if (!pi_state)
return -EINVAL;

+ spin_lock(&pi_state->pi_mutex.wait_lock);
new_owner = rt_mutex_next_owner(&pi_state->pi_mutex);

/*
@@ -604,6 +605,7 @@ static int wake_futex_pi(u32 __user *uad
pi_state->owner = new_owner;
spin_unlock_irq(&new_owner->pi_lock);

+ spin_unlock(&pi_state->pi_mutex.wait_lock);
rt_mutex_unlock(&pi_state->pi_mutex);

return 0;
--
-
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