From: Marco Elver <elver@google.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Kees Cook <keescook@chromium.org>,
Thomas Gleixner <tglx@linutronix.de>,
Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Elena Reshetova <elena.reshetova@intel.com>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Potapenko <glider@google.com>,
Jann Horn <jannh@google.com>,
Peter Collingbourne <pcc@google.com>,
kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org,
llvm@lists.linux.dev, linux-toolchains@vger.kernel.org
Subject: Re: randomize_kstack: To init or not to init?
Date: Thu, 9 Dec 2021 13:58:35 +0100 [thread overview]
Message-ID: <CANpmjNODi8sLHe8JoU-phddf++vh+1sW90b08j-yM7chsecxyg@mail.gmail.com> (raw)
In-Reply-To: <YbHaASWR07kPfabg@hirez.programming.kicks-ass.net>
On Thu, 9 Dec 2021 at 11:27, Peter Zijlstra <peterz@infradead.org> wrote:
> On Thu, Dec 09, 2021 at 10:58:01AM +0100, Marco Elver wrote:
[...]
> > There are several options:
> >
> > A. Make memset (and probably all other mem-transfer functions)
> > noinstr compatible, if that is even possible. This only solves
> > problem #2.
>
> While we can shut up objtool real easy, the bigger problem is that
> noinstr also excludes things like kprobes and breakpoints and other such
> goodness from being placed in the text.
>
> > B. A workaround could be using a VLA with
> > __attribute__((uninitialized)), but requires some restructuring
> > to make sure the VLA remains in scope and other trickery to
> > convince the compiler to not give up that stack space.
> >
> > C. Introduce a new __builtin_alloca_uninitialized().
> >
> > I think #C would be the most robust solution, but means this would
> > remain as-is for a while.
> >
> > Preferences?
>
> I'm with you on C.
Seems simple enough, so I've sent https://reviews.llvm.org/D115440 --
either way, there needs to be support to not initialize alloca'd
memory. Let's see where we end up.
next prev parent reply other threads:[~2021-12-09 12:58 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-09 9:58 randomize_kstack: To init or not to init? Marco Elver
2021-12-09 10:27 ` Peter Zijlstra
2021-12-09 12:58 ` Marco Elver [this message]
2021-12-09 20:16 ` Segher Boessenkool
2021-12-09 20:33 ` Marco Elver
2021-12-20 7:00 ` Marco Elver
2021-12-09 20:48 ` Kees Cook
2021-12-09 20:54 ` Marco Elver
2021-12-09 21:11 ` Alexander Potapenko
2021-12-10 0:01 ` Segher Boessenkool
2021-12-09 21:14 ` Kees Cook
2021-12-09 21:16 ` Jann Horn
2021-12-09 21:40 ` Marco Elver
2021-12-11 17:01 ` David Laight
2021-12-11 20:20 ` Segher Boessenkool
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