linux-kernel - RE: [PATCH v2 0/5] Optionally randomize kernel stack offset each syscall

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Date:   Wed, 25 Mar 2020 12:15:12 +0000
From:   "Reshetova, Elena" <elena.reshetova@...el.com>
To:     Kees Cook <keescook@...omium.org>, Jann Horn <jannh@...gle.com>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        the arch/x86 maintainers <x86@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Catalin Marinas <catalin.marinas@....com>,
        "Will Deacon" <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "Alexander Potapenko" <glider@...gle.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Linux-MM <linux-mm@...ck.org>,
        kernel list <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 0/5] Optionally randomize kernel stack offset each
 syscall


> > Also, are you sure that it isn't possible to make the syscall that
> > leaked its stack pointer never return to userspace (via ptrace or
> > SIGSTOP or something like that), and therefore never realign its
> > stack, while keeping some controlled data present on the syscall's
> > stack?

How would you reliably detect that a stack pointer has been leaked
to userspace while it has been in a syscall? Does not seem to be a trivial
task to me. 

Best Regards,
Elena.