linux-kernel - Re: [PATCH v4 1/2] powerpc/32: add stack protector support

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Message-ID: <20180928162625.GT23155@gate.crashing.org>
Date:   Fri, 28 Sep 2018 11:26:25 -0500
From:   Segher Boessenkool <segher@...nel.crashing.org>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     Christophe LEROY <christophe.leroy@....fr>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/2] powerpc/32: add stack protector support

On Fri, Sep 28, 2018 at 10:56:07PM +1000, Michael Ellerman wrote:
> The problem of low entropy at boot on systems without a good hardware
> source is sort of unsolvable.
> 
> As you say it's up to the core kernel/random code, we shouldn't be
> trying to do anything tricky in the arch code.
> 
> You don't want your system to take 3 hours to boot because it's waiting
> for entropy for the stack canary.
> 
> If we can update the canary later once the entropy pool is setup that
> would be ideal.

Yup, I agree with all that.

But we should *also* not say "oh, there may be cases where we cannot
do the right thing, so just do not even try, ever, anywhere".


Segher