linux-kernel - Re: [patch V2 3/5] lib/vdso/32: Provide legacy syscall fallbacks

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Date:   Tue, 30 Jul 2019 13:09:20 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Kees Cook <keescook@...omium.org>,
        Paul Bolle <pebolle@...cali.nl>, Will Deacon <will@...nel.org>
Subject: Re: [patch V2 3/5] lib/vdso/32: Provide legacy syscall fallbacks

On Tue, Jul 30, 2019 at 2:39 AM Thomas Gleixner <tglx@...utronix.de> wrote:
>
> To address the regression which causes seccomp to deny applications the
> access to clock_gettime64() and clock_getres64() syscalls because they
> are not enabled in the existing filters.
>
> That trips over the fact that 32bit VDSOs use the new clock_gettime64() and
> clock_getres64() syscalls in the fallback path.
>
> Add a conditional to invoke the 32bit legacy fallback syscalls instead of
> the new 64bit variants. The conditional can go away once all architectures
> are converted.
>

I haven't surveyed all the architectures, but once everything is
converted, shouldn't we use the 32-bit fallback for exactly the same
set of architectures that want clock_gettime32 at all in the vdso?

--Andy