linux-kernel - Re: [PATCH] mm,hwpoison: check mm when killing accessing process

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Message-ID: <20220915012626.GA1791458@hori.linux.bs1.fc.nec.co.jp>
Date:   Thu, 15 Sep 2022 10:48:43 +0900
From:   Naoya Horiguchi <naoya.horiguchi@...ux.dev>
To:     Shuai Xue <xueshuai@...ux.alibaba.com>
Cc:     linmiaohe@...wei.com, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        cuibixuan@...ux.alibaba.com, baolin.wang@...ux.alibaba.com,
        zhuo.song@...ux.alibaba.com,
        Naoya Horiguchi <naoya.horiguchi@....com>
Subject: Re: [PATCH] mm,hwpoison: check mm when killing accessing process

On Wed, Sep 14, 2022 at 02:49:35PM +0800, Shuai Xue wrote:
> The GHES code calls memory_failure_queue() from IRQ context to queue work
> into workqueue and schedule it on the current CPU. Then the work is
> processed in memory_failure_work_func() by kworker and calls
> memory_failure().
>
> When a page is already poisoned, commit a3f5d80ea401 ("mm,hwpoison: send
> SIGBUS with error virutal address") make memory_failure() call
> kill_accessing_process() that:
>
>     - holds mmap locking of current->mm
>     - does pagetable walk to find the error virtual address
>     - and sends SIGBUS to the current process with error info.
>
> However, the mm of kworker is not valid. Therefore, check mm when killing
> accessing process.
>
> Fixes: a3f5d80ea401 ("mm,hwpoison: send SIGBUS with error virutal address")
> Signed-off-by: Shuai Xue <xueshuai@...ux.alibaba.com>

Thank you for the patch, the fix itself makes sense to me.
I agree with this patch with applying comments from Andrew.

Acked-by: Naoya Horiguchi <naoya.horiguchi@....com>