Date: Tue, 14 Nov 2017 13:17:18 -0800 From: Andy Lutomirski <luto@...nel.org> To: Alexander Popov <alex.popov@...ux.com> Cc: Mark Rutland <mark.rutland@....com>, Andy Lutomirski <luto@...nel.org>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, Kees Cook <keescook@...omium.org>, PaX Team <pageexec@...email.hu>, Brad Spengler <spender@...ecurity.net>, Ingo Molnar <mingo@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Tycho Andersen <tycho@...ker.com>, Laura Abbott <labbott@...hat.com>, Ard Biesheuvel <ard.biesheuvel@...aro.org>, Borislav Petkov <bp@...en8.de>, Thomas Gleixner <tglx@...utronix.de>, "H . Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org> Subject: Re: [PATCH RFC v5 2/5] gcc-plugins: Add STACKLEAK plugin for tracking the kernel stack On Tue, Nov 14, 2017 at 1:09 PM, Alexander Popov <alex.popov@...ux.com> wrote: > Thanks, Mark! > > Please see my comments below. > > On 14.11.2017 19:33, Mark Rutland wrote: >> On Tue, Nov 14, 2017 at 08:13:43AM -0800, Andy Lutomirski wrote: >>> What does the STEAKLACK plugin actually do? I haven't followed this enough. >> >> The plugin adds instrumentation to track the maximum stack depth, though only >> functions with a sufficiently large stackframe are instrumented. > > Yes. Functions with a big stack frame call track_stack() to update the > lowest_stack value. If CONFIG_VMAP_STACK is disabled, track_stack() is compiled > with a check for detecting stack depth overflow. This check is what I'm asking > about. Then you'll probably have to do something like what I did in the VMAP_STACK code. That being said, I don't entirely see the point. If you want a hardened kernel, you're going to enable VMAP_STACK. Are there really users of hardened 32-bit kernels?
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