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    Subject[PATCH 4.14 001/156] futex: Fix OWNER_DEAD fixup
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Peter Zijlstra <peterz@infradead.org>

    commit a97cb0e7b3f4c6297fd857055ae8e895f402f501 upstream.

    Both Geert and DaveJ reported that the recent futex commit:

    c1e2f0eaf015 ("futex: Avoid violating the 10th rule of futex")

    introduced a problem with setting OWNER_DEAD. We set the bit on an
    uninitialized variable and then entirely optimize it away as a
    dead-store.

    Move the setting of the bit to where it is more useful.

    Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
    Reported-by: Dave Jones <davej@codemonkey.org.uk>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Paul E. McKenney <paulmck@us.ibm.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Fixes: c1e2f0eaf015 ("futex: Avoid violating the 10th rule of futex")
    Link: http://lkml.kernel.org/r/20180122103947.GD2228@hirez.programming.kicks-ass.net
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Cc: Ozkan Sezer <sezeroz@gmail.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    kernel/futex.c | 6 +++---
    1 file changed, 3 insertions(+), 3 deletions(-)

    --- a/kernel/futex.c
    +++ b/kernel/futex.c
    @@ -2311,9 +2311,6 @@ static int fixup_pi_state_owner(u32 __us
    raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock);

    oldowner = pi_state->owner;
    - /* Owner died? */
    - if (!pi_state->owner)
    - newtid |= FUTEX_OWNER_DIED;

    /*
    * We are here because either:
    @@ -2374,6 +2371,9 @@ retry:
    }

    newtid = task_pid_vnr(newowner) | FUTEX_WAITERS;
    + /* Owner died? */
    + if (!pi_state->owner)
    + newtid |= FUTEX_OWNER_DIED;

    if (get_futex_value_locked(&uval, uaddr))
    goto handle_fault;

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