linux-kernel - Re: Fwd: Started to get "memfd_create() without MFD_EXEC nor MFD_NOEXEC

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Message-ID: <202306010710.7F5C39B7A@keescook>
Date:   Thu, 1 Jun 2023 07:12:06 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Bagas Sanjaya <bagasdotme@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Regressions <regressions@...ts.linux.dev>,
        Linux Memory Management List <linux-mm@...ck.org>,
        Jeff Xu <jeffxu@...gle.com>,
        Daniel Verkamp <dverkamp@...omium.org>,
        David Herrmann <dh.herrmann@...il.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Hugh Dickins <hughd@...gle.com>, Jann Horn <jannh@...gle.com>,
        Jorge Lucangeli Obes <jorgelo@...omium.org>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stuart Foster <smf-linux@...ginmedia.com>
Subject: Re: Fwd: Started to get "memfd_create() without MFD_EXEC nor
 MFD_NOEXEC_SEAL"

On Thu, Jun 01, 2023 at 09:18:47AM +0200, Vlastimil Babka wrote:
> On 6/1/23 04:07, Bagas Sanjaya wrote:
> > Hi,
> > 
> > I notice a regression report on Bugzilla [1]. Quoting from it:
> > 
> >> Recent kernels seem to generate this:
> >> 
> >> "memfd_create() without MFD_EXEC nor MFD_NOEXEC_SEAL, pid=3976 'Xorg'"
> >> 
> >> Is this a kernel problem or something to do with Xorg ?
> >> 
> >> Seen in Kernels 6.3.4 and 6.4.0-rc4.
> >> 
> >> Thanks
> > 
> > See Bugzilla for the full thread and attached logs (dmesg, xorg, bisection
> > log).
> > 
> > Anyway, I'm adding it to regzbot:
> > 
> > #regzbot introduced: 105ff5339f498a https://bugzilla.kernel.org/show_bug.cgi?id=217508
> > #regzbot title: memfd_create() without MFD_EXEC nor MFD_NOEXEC_SEAL on Xorg
> 
> Hm indeed it seems to have introduced 2 new flags and immediately warn if
> any process doesn't use them. Maybe it would make sense for some of the
> non-default values of vm.memfd_noexec, but it's too early to warn
> unconditionally everywhere, no?

This is pretty standard for getting new options like this noticed by
userspace -- there is no regression in _behavior_. It's just a reminder
to fix userspace code.

-Kees

> > 
> > [1]: https://bugzilla.kernel.org/show_bug.cgi?id=217508
> > 
> 

-- 
Kees Cook