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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Fri, 11 May 2018 09:45:33 -0700
Message-ID: <CA+55aFxYwH6dw=bsQJHEgkM_iZfVNerqn+RAXrrY2iufJag6Qw@mail.gmail.com>
Subject: Re: [PATCH v5 5/7] proc: instantiate only pids that we can ptrace on
 'limit_pids=1' mount option
To:     gladkov.alexey@gmail.com
Cc:     Kees Cook <keescook@chromium.org>,
        Andrew Lutomirski <luto@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
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        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
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        Oleg Nesterov <oleg@redhat.com>,
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On Fri, May 11, 2018 at 2:46 AM Alexey Gladkov <gladkov.alexey@gmail.com>
wrote:

> +       /* Limit procfs to only ptracable tasks */
> +       if (limit_pids == PROC_LIMIT_PIDS_PTRACE) {
> +               cond_resched();
> +               if (!has_pid_permissions(fs_info, task,
HIDEPID_NO_ACCESS))
> +                       goto out_put_task;
> +       }

Where did that "cond_resched()" come from? That doesn't seem to make a lot
of sense.

                    Linus