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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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