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

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Date:   Wed, 27 Apr 2022 14:26:58 +0200
From:   Marco Elver <elver@...gle.com>
To:     Jun Miao <jun.miao@...el.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 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>

> > ---
> >   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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