Re: [PATCH] mm/migrate: Avoid possible unnecessary ptrace_may_access() call in kernel_move_pages()

[linmiaohe]

Kees Cook <keescook@xxxxxxxxxxxx> 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@xxxxxxxxxx>
>> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
>
>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.