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

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Date:   Fri, 16 Dec 2022 14:06:41 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Jeff Xu <jeffxu@...gle.com>
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, 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?

--- 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));
 	}
_