linux-kernel - Re: [PATCH] um: Prevent KASAN splats in dump

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Message-ID: <CACT4Y+aBpkfgEvM6rE9Kg5U0MwcHnUA+Fm_2F4g9A4QQ3hav4g@mail.gmail.com>
Date:   Wed, 7 Sep 2022 12:29:55 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Vincent Whitchurch <vincent.whitchurch@...s.com>
Cc:     Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Johannes Berg <johannes@...solutions.net>, kernel@...s.com,
        Patricia Alfonso <trishalfonso@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        linux-um@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] um: Prevent KASAN splats in dump_stack()

On Wed, 7 Sept 2022 at 12:05, Vincent Whitchurch
<vincent.whitchurch@...s.com> wrote:
>
> Use READ_ONCE_NOCHECK() when reading the stack to prevent KASAN splats
> when dump_stack() is used.
>
> Fixes: 5b301409e8bc5d7fad ("UML: add support for KASAN under x86_64")
> Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>

Reviewed-by: Dmitry Vyukov <dvyukov@...gle.com>

> ---
>  arch/um/kernel/sysrq.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/um/kernel/sysrq.c b/arch/um/kernel/sysrq.c
> index 7452f70d50d0..746715379f12 100644
> --- a/arch/um/kernel/sysrq.c
> +++ b/arch/um/kernel/sysrq.c
> @@ -48,7 +48,8 @@ void show_stack(struct task_struct *task, unsigned long *stack,
>                         break;
>                 if (i && ((i % STACKSLOTS_PER_LINE) == 0))
>                         pr_cont("\n");
> -               pr_cont(" %08lx", *stack++);
> +               pr_cont(" %08lx", READ_ONCE_NOCHECK(*stack));
> +               stack++;
>         }
>
>         printk("%sCall Trace:\n", loglvl);
> --
> 2.34.1
>