Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Thu, 6 Feb 2020 13:32:48 -0800
From:   Kees Cook <keescook@chromium.org>
To:     Arvind Sankar <nivedita@alum.mit.edu>
Cc:     Kristen Carlson Accardi <kristen@linux.intel.com>,
        tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com,
        arjan@linux.intel.com, rick.p.edgecombe@intel.com, x86@kernel.org,
        linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com
Subject: Re: [RFC PATCH 11/11] x86/boot: Move "boot heap" out of .bss
Message-ID: <202002061331.E5956EA@keescook>
References: <20200205223950.1212394-1-kristen@linux.intel.com>
 <20200205223950.1212394-12-kristen@linux.intel.com>
 <20200206001103.GA220377@rani.riverdale.lan>
 <202002060251.681292DE63@keescook>
 <20200206142557.GA3033443@rani.riverdale.lan>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20200206142557.GA3033443@rani.riverdale.lan>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, Feb 06, 2020 at 09:25:59AM -0500, Arvind Sankar wrote:
> On Thu, Feb 06, 2020 at 03:13:12AM -0800, Kees Cook wrote:
> > Yes, thank you for the reminder. I couldn't find the ZO_INIT_SIZE when I
> > was staring at this, since I only looked around the compressed/ directory.
> > :)
> > 
> 
> There's another thing I noticed -- you would need to ensure that the
> init_size in the header covers your boot heap even if you did split it
> out. The reason is that the bootloader will only know to reserve enough
> memory for init_size: it's possible it might put the initrd or something
> else following the kernel, or theoretically there might be reserved
> memory regions or the end of physical RAM immediately following, so you
> can't assume that area will be available when you get to extract_kernel.

Yeah, that's what I was worrying about after I wrote that patch. Yours
is the correct solution. :) (I Acked both of those now).

-- 
Kees Cook