linux-kernel - Re: Wanted: simple, safe x86 stack overflow detection

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Date:	Sat, 3 Mar 2007 17:50:31 -0800
From:	Bill Irwin <bill.irwin@...cle.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Chuck Ebbert <cebbert@...hat.com>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Wanted: simple, safe x86 stack overflow detection

On Wed, Feb 28, 2007 at 09:41:44PM +0100, Andi Kleen wrote:
> I suppose one could have a CONFIG_DEBUG_STACK_OVERFLOW that gets
> the stacks from vmalloc which would catch any overflow with its
> guard pages. This is you would need to change __pa() to handle
> that too because there might be still some drivers that do
> DMA on stack addresses.  Would be somewhat ugly but doable.
> But I have my doubts it is worth it again -- in my experience static
> analysis works well enough to trace them down and 
> there are not that many anyways.

In case anyone wants them, patches against v2.6.21-rc2-116-gbb648a0
for this are available from http://oss.oracle.com/~wli/stack_paranoia/

I only did arch/i386/ as per the Linux tradition, though I could
arrange for other arches easily enough, barring those for which I lack
target platforms. Testbooted on qemu -smp 4 with 64KB vmalloc()'d
stacks and IRQ stacks, compiletested in a couple of other configs.
Translation: very light testing. For me this was about reestablishing
reconnoiter of current mainline and familiarizing myself with qemu.

The patch series goes something like:
$ quilt series | xargs -i grep -nH '^Subj' patches/\{\} | cut -f2 -d/ |
cut -f 4 -d: | cat -n
     1   make stack size configurable
     2   add config option to vmalloc stacks
     3   make IRQ stacks independently configurable
     4   go BUG on vmallocspace in __pa()
     5   dynamically allocate IRQ stacks
     6   arrange for a guard page on cpu 0's IRQ stack

Chuck, is any of this of any use to you?


-- wli
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