[tip:sched/core] stop_machine: Remove cpu_stop_work' s from list in cpu_stop_park()

[tip-bot for Oleg Nesterov]

Commit-ID:  d308b9f1e4412bcf583c82c4ca15ef97cb8b0e6f
Gitweb:     http://git.kernel.org/tip/d308b9f1e4412bcf583c82c4ca15ef97cb8b0e6f
Author:     Oleg Nesterov <oleg@xxxxxxxxxx>
AuthorDate: Tue, 30 Jun 2015 03:29:58 +0200
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Mon, 3 Aug 2015 12:21:28 +0200

stop_machine: Remove cpu_stop_work's from list in cpu_stop_park()

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@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: dave@xxxxxxxxxxxx
Cc: der.herr@xxxxxxx
Cc: paulmck@xxxxxxxxxxxxxxxxxx
Cc: riel@xxxxxxxxxx
Cc: viro@xxxxxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/20150630012958.GA23944@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 kernel/stop_machine.c | 6 ++++--
 1 file 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);
 }
--
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