linux-kernel - Re: [PATCH 2/6] x86/boot: Move compressed kernel to end of decompression buffer

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 16 Aug 2016 19:25:55 -0700
From:	Matt Mullins <mmullins@...x.us>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Kees Cook <keescook@...omium.org>, Ingo Molnar <mingo@...nel.org>,
	Ingo Molnar <mingo@...hat.com>, Baoquan He <bhe@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
	Vivek Goyal <vgoyal@...hat.com>,
	Andy Lutomirski <luto@...nel.org>,
	Lasse Collin <lasse.collin@...aani.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Young <dyoung@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Simon Glass <sjg@...omium.org>
Subject: Re: [PATCH 2/6] x86/boot: Move compressed kernel to end of
 decompression buffer

On Tue, Aug 16, 2016 at 12:19:42PM -0700, Yinghai Lu wrote:
> On Mon, Aug 15, 2016 at 9:01 PM, Matt Mullins <mmullins@...x.us> wrote:
> >
> > This appears to have a negative effect on booting the Intel Edison platform, as
> > it uses u-boot as its bootloader.  u-boot does not copy the init_size parameter
> > when booting a bzImage: it copies a fixed-size setup_header [1], and its
> > definition of setup_header doesn't include the parameters beyond setup_data [2].
> >
> > With a zero value for init_size, this calculates a %rsp value of 0x101ff9600.
> > This causes the boot process to hard-stop at the immediately-following pushq, as
> > this platform has no usable physical addresses above 4G.
> >
> > What are the options for getting this type of platform to function again?  For
> > now, kexec from a working Linux system does seem to be a work-around, but there
> > appears to be other x86 hardware using u-boot: the chromium.org folks seem to be
> > maintaining the u-boot x86 tree.
> >
> > [1] http://git.denx.de/?p=u-boot.git;a=blob;f=arch/x86/lib/zimage.c;h=1b33c771391f49ffe82864ff1582bdfd07e5e97d;hb=HEAD#l156
> > [2] http://git.denx.de/?p=u-boot.git;a=blob;f=arch/x86/include/asm/bootparam.h;h=140095117e5a2daef0a097c55f0ed10e08acc781;hb=HEAD#l24
> 
> Then should fix the u-boot about header_size assumption.

I was hoping to avoid that, since the Edison's u-boot is 10,000-line patch atop
the upstream -- I don't trust myself to build and flash one quite yet.

If this turned out to affect Chromebooks, I'd spend more effort pushing for
a kernel fix, but it seems that ChromeOS has a different kernel load procedure
and doesn't use "zboot".  For now, I'll probably just keep a local patch that
hard-codes a value large enough to decompress and launch the kernel.

I may turn that local patch into something gated by a Kconfig eventually, in
hopes that users of the other x86 u-boot platforms will see it in a "make
oldconfig" run.