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From:   Daniel Micay <danielmicay@gmail.com>
Date:   Mon, 29 Oct 2018 04:55:07 -0400
Message-ID: <CA+DvKQKUCVN5OUxShwxhXUnx5Qx0EUZSCeKOAUYR2CWW+NkO_g@mail.gmail.com>
Subject: Re: [PATCH 1/2] x86/pkeys: copy pkey state at fork()
To:     Ingo Molnar <mingo@kernel.org>
Cc:     Andy Lutomirski <luto@amacapital.net>,
        Dave Hansen <dave.hansen@intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        kernel list <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H . Peter Anvin" <hpa@zytor.com>, X86 ML <x86@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Will Deacon <will.deacon@arm.com>,
        Andy Lutomirski <luto@kernel.org>, jroedel@suse.de
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Yeah, a no-op pkey_alloc flag tied to this patch to provide a way to
detect if pkey state is preserved on fork, since kernels without the
patch would report EINVAL. Something like
PKEY_ASSERT_FORK_INHERIT_STATE would make sense. Otherwise, it's
going to be quite painful to adopt this in userspace software without kernel
version checks. Most software can't accept causing a crash / abort
after forking in environments not applying all the stable kernel
patches, or in fresh OS installs that aren't fully updated + rebooted yet.