linux-kernel - [PATCH 5/5] stop_machine: cpu_stop_park() should remove cpu_stop

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Message-ID: <20150630012958.GA23944@redhat.com>
Date:	Tue, 30 Jun 2015 03:29:58 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>, Tejun Heo <tj@...nel.org>
Cc:	paulmck@...ux.vnet.ibm.com, mingo@...hat.com, der.herr@...r.at,
	dave@...olabs.net, riel@...hat.com, viro@...IV.linux.org.uk,
	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: [PATCH 5/5] stop_machine: cpu_stop_park() should remove
	cpu_stop_work's from list

cpu_stop_park() does cpu_stop_signal_done() but leaves the work on
stopper->works. The owner of this work can free/reuse this memory
right after that and corrupt the list, so if this CPU becomes online
again cpu_stopper_thread() will crash.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 kernel/stop_machine.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 9a70def..12484e5 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -462,13 +462,15 @@ static void cpu_stop_create(unsigned int cpu)
 static void cpu_stop_park(unsigned int cpu)
 {
 	struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
-	struct cpu_stop_work *work;
+	struct cpu_stop_work *work, *tmp;
 	unsigned long flags;
 
 	/* drain remaining works */
 	spin_lock_irqsave(&stopper->lock, flags);
-	list_for_each_entry(work, &stopper->works, list)
+	list_for_each_entry_safe(work, tmp, &stopper->works, list) {
+		list_del_init(&work->list);
 		cpu_stop_signal_done(work->done, false);
+	}
 	stopper->enabled = false;
 	spin_unlock_irqrestore(&stopper->lock, flags);
 }
-- 
1.5.5.1

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