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Date: Mon, 14 May 2018 15:07:15 +0100
From: Mark Rutland <>
To: Alexander Popov <>
Cc: Andy Lutomirski <>, Laura Abbott <>,
	Kees Cook <>,
	Ard Biesheuvel <>,,,
Subject: Re: [PATCH 2/2] arm64: Clear the stack

On Mon, May 14, 2018 at 04:53:12PM +0300, Alexander Popov wrote:
> On 14.05.2018 13:06, Mark Rutland wrote:
> > I think it is reasonable to panic() here even with CONFIG_VMAP_STACK
> > selected.
> It's too tough for CONFIG_VMAP_STACK on x86 - the system can proceed to live.
> Anyway, the check_alloca() code will not be shared between x86 and arm64, I've
> described the reasons in this thread. So I can have BUG() for CONFIG_VMAP_STACK
> on x86 and Laura can consistently use panic() on arm64.

If we need arch-specific implementations anyway, then that's fine by me.

> >> So we should not do it in check_alloca() as well, just use BUG() and
> >> hope for the best.
> > 
> > Regardless of whether we BUG() or panic(), we're hoping for the best.
> > 
> > Consistently using panic() here will keep things simpler, so any failure
> > reported will be easier to reason about, and easier to debug.
> Let me keep BUG() for !CONFIG_SCHED_STACK_END_CHECK. I beware of using panic()
> by default, let distro/user decide this. I remember very well how I was shouted
> at, when this one was merged:

Sure; my comments needn't hold up your patches.


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