futex: Fix handling of bad requeue syscall pairing

If futex_requeue(requeue_pi=1) finds a futex_q that was created by a call
other the futex_wait_requeue_pi(), the q.rt_waiter may be null.  If so,
this will result in an oops from the following call graph:

futex_requeue()
  rt_mutex_start_proxy_lock()
    task_blocks_on_rt_mutex()
      waiter->task dereference
        OOPS

We currently WARN_ON() if this is detected, clearly this is inadequate.
If we detect a mispairing in futex_requeue(), bail out, seding -EINVAL to
user-space.

V2: Fix parenthesis warnings.

Signed-off-by: Darren Hart <[email protected]>
Acked-by: Peter Zijlstra <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: John Kacur <[email protected]>
Cc: Eric Dumazet <[email protected]>
Cc: Dinakar Guniguntala <[email protected]>
Cc: John Stultz <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>

0 files changed, 0 insertions, 0 deletions