linux-kernel - Re: [PATCH 1/2] boot: increase stack size for kernel boot loader decompressor

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: Windows password security audit tool. GUI, reports in PDF.

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

Date:	Tue, 08 Apr 2008 07:56:01 -0700
From:	Mike Travis <travis@....com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Alexander van Heukelum <heukelum@...lshack.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, heukelum@...tmail.fm,
	Yinghai Lu <yhlu.kernel@...il.com>
Subject: Re: [PATCH 1/2] boot: increase stack size for kernel boot loader
 decompressor

Ingo Molnar wrote:
> * Alexander van Heukelum <heukelum@...lshack.com> wrote:
> 
>> I did see that the malloc space that the inflate code is using is 
>> taken from _after_ the end of the bss. I don't see how this is 
>> protected from being used/overwritten. Changing the stack size changes 
>> the memory layout a bit... maybe you were so unlucky to create a 
>> vmlinux image that was just barely smaller than some threshold and 
>> increasing the stack size made the decompression/relocation area be 
>> located somewhere else?
>>
>> Test patch follows.
> 
> that's a really interesting theory.
> 
> FWIIW, i've been booting allyesconfig bzImages for a long time (with 
> only minimal amount of drivers disabled - mostly old ISA ones that 
> assume the presence of the real hardware), and they boot and work fine 
> on both 32-bit and 64-bit typical whitebox PCs. That means huge bzImages 
> that decompresses into a ~41 MB kernel image. I'd expect that to be a 
> rather severe test of the decompressor.
> 
> 	Ingo

Well admittedly, I did discover this problem way early in booting
up a 4k NR_CPU kernel (obviously ;-).  Once it booted, I haven't
revisited that problem again.  I wonder if it's a pathological case
of a single bitstream that causes expansion instead of compression?
Note I was using the akpm2 config script with NR_CPUS=4096 and
NODES_SHIFT=9 (plus some other tweaks specific to our AMD and Intel
boxes.)

Thanks,
Mike
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/