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    Subject[PATCH 4.14 117/159] locking/lockdep: Fix possible NULL deref
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

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

    From: Peter Zijlstra <peterz@infradead.org>


    [ Upstream commit 5e351ad106997e06b2dc3da9c6b939b95f67fb88 ]

    We can't invalidate xhlocks when we've not yet allocated any.

    Reported-by: Dmitry Vyukov <dvyukov@google.com>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: linux-kernel@vger.kernel.org
    Fixes: f52be5708076 ("locking/lockdep: Untangle xhlock history save/restore from task independence")
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    kernel/locking/lockdep.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    --- a/kernel/locking/lockdep.c
    +++ b/kernel/locking/lockdep.c
    @@ -4777,7 +4777,8 @@ void lockdep_invariant_state(bool force)
    * Verify the former, enforce the latter.
    */
    WARN_ON_ONCE(!force && current->lockdep_depth);
    - invalidate_xhlock(&xhlock(current->xhlock_idx));
    + if (current->xhlocks)
    + invalidate_xhlock(&xhlock(current->xhlock_idx));
    }

    static int cross_lock(struct lockdep_map *lock)

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