linux-kernel - Re: [PATCH] irq_work: Make irq_work_queue

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Date:   Wed, 27 Apr 2022 21:17:52 +0800
From:   Jun Miao <jun.miao@...el.com>
To:     Marco Elver <elver@...gle.com>
CC:     <ryabinin.a.a@...il.com>, Dmitry Vyukov <dvyukov@...gle.com>,
        <bigeasy@...utronix.de>, <qiang1.zhang@...el.com>,
        <peterz@...radead.org>, <akpm@...ux-foundation.org>,
        <andreyknvl@...il.com>, <ying.huang@...el.com>,
        <kasan-dev@...glegroups.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] irq_work: Make irq_work_queue_on() NMI-safe again


On 2022/4/27 20:26, Marco Elver wrote:
> On Wed, 27 Apr 2022 at 03:49, Jun Miao <jun.miao@...el.com> wrote:
>> Add  To/Cc : KASAN/MEM , since I only used the scripts/get_maintainer.pl
>> to irq_work.c file.
>>
>> Thanks
>> Jun Miao
>>
>>
>> On 2022/4/26 21:49, Jun Miao wrote:
>>> We should not put NMI unsafe code in irq_work_queue_on().
>>>
>>> The KASAN of kasan_record_aux_stack_noalloc() is not NMI safe. Because which
>>> will call the spinlock. While the irq_work_queue_on() is also very carefully
>>> carafted to be exactly that.
> "crafted"
>
>>> When unable CONFIG_SM or local CPU, the irq_work_queue_on() is even same to
> CONFIG_SM -> CONFIG_SMP
>
>>> irq_work_queue(). So delete KASAN instantly.
>>>
>>> Fixes: e2b5bcf9f5ba ("irq_work: record irq_work_queue() call stack")
>>> Suggested by: "Huang, Ying" <ying.huang@...el.com>
>>> Signed-off-by: Jun Miao <jun.miao@...el.com>
> I thought this had already been removed, but apparently there were 2
> places: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=156172a13ff0626d8e23276e741c7e2cb2f3b572
>
> Acked-by: Marco Elver <elver@...gle.com>

Sure, I also found this patch which is the same reason, maybe Peter Z 
forgot it. Let me make up a little.😉

Send V2 later.

Thanks
Jun Miao
>>> ---
>>>    kernel/irq_work.c | 3 ---
>>>    1 file changed, 3 deletions(-)
>>>
>>> diff --git a/kernel/irq_work.c b/kernel/irq_work.c
>>> index 7afa40fe5cc4..e7f48aa8d8af 100644
>>> --- a/kernel/irq_work.c
>>> +++ b/kernel/irq_work.c
>>> @@ -20,7 +20,6 @@
>>>    #include <linux/smp.h>
>>>    #include <linux/smpboot.h>
>>>    #include <asm/processor.h>
>>> -#include <linux/kasan.h>
>>>
>>>    static DEFINE_PER_CPU(struct llist_head, raised_list);
>>>    static DEFINE_PER_CPU(struct llist_head, lazy_list);
>>> @@ -137,8 +136,6 @@ bool irq_work_queue_on(struct irq_work *work, int cpu)
>>>        if (!irq_work_claim(work))
>>>                return false;
>>>
>>> -     kasan_record_aux_stack_noalloc(work);
>>> -
>>>        preempt_disable();
>>>        if (cpu != smp_processor_id()) {
>>>                /* Arch remote IPI send/receive backend aren't NMI safe */
>> --
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