linux-kernel - Re: [PATCH v6 3/6] mm/memfd: add MFD_NOEXEC_SEAL and MFD

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Date:   Fri, 16 Dec 2022 15:40:00 -0800
From:   Jeff Xu <jeffxu@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Kees Cook <keescook@...omium.org>, Peter Xu <peterx@...hat.com>,
        jeffxu@...omium.org, skhan@...uxfoundation.org,
        dmitry.torokhov@...il.com, dverkamp@...omium.org, hughd@...gle.com,
        jorgelo@...omium.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-mm@...ck.org,
        jannh@...gle.com, linux-hardening@...r.kernel.org,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v6 3/6] mm/memfd: add MFD_NOEXEC_SEAL and MFD_EXEC

On Fri, Dec 16, 2022 at 2:06 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
>
> On Fri, 16 Dec 2022 13:46:58 -0800 Jeff Xu <jeffxu@...gle.com> wrote:
>
> > On Fri, Dec 16, 2022 at 12:35 PM Kees Cook <keescook@...omium.org> wrote:
> > >
> > > On Fri, Dec 16, 2022 at 10:11:44AM -0800, Jeff Xu wrote:
> > > > Once per boot seems too little, it would be nice if we can list all processes.
> > > > I agree ratelimited might be too much.
> > > > There is a feature gap here for logging.
> > > >
> > > > Kees, what do you think ?
> > >
> > > I agree once per boot is kind of frustrating "I fixed the one warning,
> > > oh, now it's coming from a different process". But ratelimit is, in
> > > retrospect, still too often.
> > >
> > > Let's go with per boot -- this should be noisy "enough" to get the
> > > changes in API into the callers without being too much of a hassle.
> > >
> > Agreed.  Let's go with per boot.
> >
> > Hi Andrew, what is your preference ? I can send a patch  or you
> > directly fix it in mm-unstable ?
>
> Like this?
>
Yes. Thanks!

> --- a/mm/memfd.c~mm-memfd-add-mfd_noexec_seal-and-mfd_exec-fix-3
> +++ a/mm/memfd.c
> @@ -308,7 +308,7 @@ SYSCALL_DEFINE2(memfd_create,
>                         flags |= MFD_NOEXEC_SEAL;
>                         break;
>                 default:
> -                       pr_warn_ratelimited(
> +                       pr_warn_once(
>                                 "memfd_create(): MFD_NOEXEC_SEAL is enforced, pid=%d '%s'\n",
>                                 task_pid_nr(current), get_task_comm(comm, current));
>                         return -EINVAL;
> @@ -316,7 +316,7 @@ SYSCALL_DEFINE2(memfd_create,
>  #else
>                 flags |= MFD_EXEC;
>  #endif
> -               pr_warn_ratelimited(
> +               pr_warn_once(
>                         "memfd_create() without MFD_EXEC nor MFD_NOEXEC_SEAL, pid=%d '%s'\n",
>                         task_pid_nr(current), get_task_comm(comm, current));
>         }
> _
>