From: Aleksa Sarai <cyphar@cyphar.com>
To: Florian Weimer <fweimer@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Damian Tometzki <dtometzki@fedoraproject.org>,
Shuah Khan <shuah@kernel.org>, Jeff Xu <jeffxu@google.com>,
Kees Cook <keescook@chromium.org>,
Daniel Verkamp <dverkamp@chromium.org>,
Christian Brauner <brauner@kernel.org>,
Dominique Martinet <asmadeus@codewreck.org>,
stable@vger.kernel.org, linux-api@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
linux-kselftest@vger.kernel.org
Subject: Re: [PATCH v2 3/5] memfd: improve userspace warnings for missing exec-related flags
Date: Wed, 6 Sep 2023 16:58:41 +1000 [thread overview]
Message-ID: <20230906.065211-swollen.overhaul.chosen.plan-vGnGFFTg39x8@cyphar.com> (raw)
In-Reply-To: <8734zs7ft6.fsf@oldenburg.str.redhat.com>
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On 2023-09-05, Florian Weimer <fweimer@redhat.com> wrote:
> * Andrew Morton:
>
> > OK, thanks, I'll revert this. Spamming everyone even harder isn't a
> > good way to get developers to fix their stuff.
>
> Is this really buggy userspace? Are future kernels going to require
> some of these flags?
>
> That's going to break lots of applications which use memfd_create to
> enable run-time code generation on locked-down systems because it looked
> like a stable interface (“don't break userspace” and all that).
There is no userspace breakage with the current behaviour and obviously
actually requiring these flags to be passed by default would be a pretty
clear userspace breakage and would never be merged.
The original intention (as far as I can tell -- the logging behaviour
came from the original patchset) was to try to incentivise userspace to
start passing the flags so that if distributions decide to set
vm.memfd_noexec=1 as a default setting you won't end up with programs
that _need_ executable memfds (such as container runtimes) crashing
unexpectedly. I also suspect there was an aspect of "well, userspace
*should* be passing these flags after we've introduced them".
I'm sending a patch to just remove this part of the logging because I
don't think it makes sense if you can't rate-limit it sanely, and
there's probably an argument to be made that it doesn't make sense at
all (at least for the default vm.memfd_noexec=0 setting).
--
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
<https://www.cyphar.com/>
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next prev parent reply other threads:[~2023-09-06 6:59 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-14 8:40 [PATCH v2 0/5] memfd: cleanups for vm.memfd_noexec Aleksa Sarai
2023-08-14 8:40 ` [PATCH v2 1/5] selftests: memfd: error out test process when child test fails Aleksa Sarai
2023-08-14 8:40 ` [PATCH v2 2/5] memfd: do not -EACCES old memfd_create() users with vm.memfd_noexec=2 Aleksa Sarai
2023-08-14 8:40 ` [PATCH v2 3/5] memfd: improve userspace warnings for missing exec-related flags Aleksa Sarai
2023-08-22 9:10 ` Christian Brauner
2023-09-01 5:13 ` Damian Tometzki
2023-09-02 22:58 ` Andrew Morton
2023-09-04 7:09 ` Aleksa Sarai
2023-09-05 16:20 ` Florian Weimer
2023-09-06 6:58 ` Aleksa Sarai [this message]
2023-08-14 8:41 ` [PATCH v2 4/5] memfd: replace ratcheting feature from vm.memfd_noexec with hierarchy Aleksa Sarai
2023-08-16 5:13 ` Jeff Xu
2023-08-16 5:44 ` Dominique Martinet
2023-08-16 22:46 ` Jeff Xu
2023-08-14 8:41 ` [PATCH v2 5/5] selftests: improve vm.memfd_noexec sysctl tests Aleksa Sarai
2023-08-16 5:08 ` [PATCH v2 0/5] memfd: cleanups for vm.memfd_noexec Jeff Xu
2023-08-19 2:50 ` Aleksa Sarai
2023-08-21 19:04 ` Jeff Xu
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