linux-kernel - Re: [PATCH] mm/madvise: fix potential pte_unmap

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Date:   Mon, 18 Apr 2022 21:09:51 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Miaohe Lin <linmiaohe@...wei.com>
Cc:     <minchan@...nel.org>, <hannes@...xchg.org>, <mhocko@...e.com>,
        <hughd@...gle.com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm/madvise: fix potential pte_unmap_unlock pte error

On Sat, 16 Apr 2022 16:14:16 +0800 Miaohe Lin <linmiaohe@...wei.com> wrote:

> We can't assume pte_offset_map_lock will return same orig_pte value. So
> it's necessary to reacquire the orig_pte or pte_unmap_unlock will unmap
> the stale pte.

hm, where did you learn this info about pte_offset_map_lock()?

I assume this is from code inspection only?  No observed runtime failures?