Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit a97cb0e7 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

futex: Fix OWNER_DEAD fixup 



Both Geert and DaveJ reported that the recent futex commit:

  c1e2f0ea ("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: default avatarGeert Uytterhoeven <geert@linux-m68k.org>
Reported-by: default avatarDave Jones <davej@codemonkey.org.uk>
Signed-off-by: default avatarPeter 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: c1e2f0ea ("futex: Avoid violating the 10th rule of futex")
Link: http://lkml.kernel.org/r/20180122103947.GD2228@hirez.programming.kicks-ass.net


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 1f07476e

kernel/futex.c

+3 −3
Original line number Diff line number Diff line
@@ -2311,9 +2311,6 @@ static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q, 
	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 @@ static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q, 
	}



	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;