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

Kees Cook [off-list ref] wrote:

On Mon, Aug 17, 2020 at 07:59:33AM -0400, Miaohe Lin wrote:

quoted

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 <redacted>
Signed-off-by: Miaohe Lin <linmiaohe@huawei.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.