linux-kernel - [PATCH 1/8] stop_machine: cpu_stopper

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Message-ID: <20151115193311.GA8242@redhat.com>
Date:	Sun, 15 Nov 2015 20:33:11 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>
Cc:	Milos Vyletel <milos@...hat.com>,
	Prarit Bhargava <prarit@...hat.com>, Tejun Heo <tj@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/8] stop_machine: cpu_stopper_thread() must check done !=
	NULL

stop_one_cpu_nowait(fn) will crash the kernel if the callback returns
nonzero, work->done == NULL in this case.

This needs more cleanups, cpu_stop_signal_done() is called right after
we check done != NULL and it does the same check.

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

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 867bc20..1a66a95 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -454,7 +454,7 @@ repeat:
 		preempt_disable();
 
 		ret = fn(arg);
-		if (ret)
+		if (ret && done)
 			done->ret = ret;
 
 		/* restore preemption and check it's still balanced */
-- 
1.5.5.1

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