linux-kernel - Re: [PATCH] mm/migrate: Avoid possible unnecessary ptrace_may_access() call in kernel_move

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Message-ID: <9ce6209f41b64734b2cac748783aa441@huawei.com>
Date:   Thu, 20 Aug 2020 02:18:21 +0000
From:   linmiaohe <linmiaohe@...wei.com>
To:     Kees Cook <keescook@...omium.org>
CC:     "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH] mm/migrate: Avoid possible unnecessary
 ptrace_may_access() call in kernel_move_pages()

Kees Cook <keescook@...omium.org> wrote:
>On Mon, Aug 17, 2020 at 07:59:33AM -0400, Miaohe Lin wrote:
>> There is no need to check if this process has the right to modify the 
>> specified process when they are same.
>> 
>> Signed-off-by: Hongxiang Lou <louhongxiang@...wei.com>
>> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
>
>NAK, please don't do this -- the ptrace and security hooks already do these kinds of self-introspection checks, and I'd like to keep a central place to perform these kinds of checks.
>

Many thanks for your reply.
We also avoid get_task_struct/ put_task_struct pair of atomic ops, rcu_lock, task_lock and so on this way.

>Is there a specific problem you've encountered that this fixes?
>

I'am sorry but there's no specific problem. I do this mainly to skip the unnecessary ptrace and security hooks.

>--
>Kees Cook

Thanks again.