linux-kernel - Re: 3.12.0-rc5+ reproducible crash at kernel/timer.c:1117

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Date:	Thu, 17 Oct 2013 15:20:15 +0300
From:	Janne Karhunen <janne.karhunen@...il.com>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: 3.12.0-rc5+ reproducible crash at kernel/timer.c:1117

On Tue, Oct 15, 2013 at 10:41 AM, Janne Karhunen
<janne.karhunen@...il.com> wrote:

>> call_timer_fn 0x73/0x160 <--- EIP hits 0
>
> Use after free.. with CONFIG_DEBUG_PAGEALLOC &&
> CONFIG_DEBUG_OBJECTS_TIMERS we get :
>
> call_timer_fn 0x73/0x160
> destroy_timer_on_stack 0x20/0x20
> ftrace_raw_event_hrtimer_expire_entry 0x3b/0xc0
> run_timer_softirq 0x1f2/0x230

Sadly no time to hunt the free at the moment, so working around temporarily by

diff --git a/kernel/timer.c b/kernel/timer.c
index 4296d13..fc7ef44 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -1094,6 +1094,9 @@ static void call_timer_fn(struct timer_list
*timer, void (*fn)(unsigned long),
 {
        int preempt_count = preempt_count();

+       if (fn == NULL)
+               return;
+

Hoping someone wiser catches the real fix at some point.


-- 
Janne
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