From a97cb0e7b3f4c6297fd857055ae8e895f402f501 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Mon, 22 Jan 2018 11:39:47 +0100
Subject: [PATCH] futex: Fix OWNER_DEAD fixup
Git-commit: a97cb0e7b3f4c6297fd857055ae8e895f402f501
Patch-mainline: v4.15
References: bsc#1067665
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>
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
kernel/futex.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/futex.c b/kernel/futex.c
index 62b04226ff82..1fbfe90733cc 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2298,9 +2298,6 @@ 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:
@@ -2361,6 +2358,9 @@ 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;
--
2.13.6