kernel-hardening - Re: [PATCH v2 1/5] fs: Add support for an O_MAYEXEC flag on sys

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Message-ID: <87ef0te7v3.fsf@oldenburg2.str.redhat.com>
Date: Fri, 06 Sep 2019 17:56:32 +0200
From: Florian Weimer <fweimer@...hat.com>
To: Mickaël Salaün <mic@...ikod.net>
Cc: linux-kernel@...r.kernel.org,  Aleksa Sarai <cyphar@...har.com>,  Alexei
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 <thibaut.sautereau@....gouv.fr>,  Vincent Strubel
 <vincent.strubel@....gouv.fr>,  Yves-Alexis Perez
 <yves-alexis.perez@....gouv.fr>,  kernel-hardening@...ts.openwall.com,
  linux-api@...r.kernel.org,  linux-security-module@...r.kernel.org,
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Subject: Re: [PATCH v2 1/5] fs: Add support for an O_MAYEXEC flag on sys_open()

Let's assume I want to add support for this to the glibc dynamic loader,
while still being able to run on older kernels.

Is it safe to try the open call first, with O_MAYEXEC, and if that fails
with EINVAL, try again without O_MAYEXEC?

Or do I risk disabling this security feature if I do that?

Do we need a different way for recognizing kernel support.  (Note that
we cannot probe paths in /proc for various reasons.)

Thanks,
Florian

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