From owner-freebsd-security  Sun Mar 24 14:25:54 2002
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Date: Sun, 24 Mar 2002 17:35:16 -0500
From: Jake Burkholder <jake@locore.ca>
To: Andrew Griffiths <nullptr@tasmail.com>
Cc: security@FreeBSD.ORG
Subject: Re: page fault.
Message-ID: <20020324173516.V90182@locore.ca>
References: <200203242143.g2OLh4523143@franklin.nt.tas.gov.au>
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In-Reply-To: <200203242143.g2OLh4523143@franklin.nt.tas.gov.au>; from nullptr@tasmail.com on Mon, Mar 25, 2002 at 08:43:05AM +1100
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Apparently, On Mon, Mar 25, 2002 at 08:43:05AM +1100,
	Andrew Griffiths said words to the effect of;

> Hello,
> 
> While testing some code to show the stack ranges on systems, I noticed that freebsd wouldn't segfault when it accessed memory below esp, or the stack bottom.
> 
> Not sure whether its a problem, but I think its worth noting.

You mean numerically higher addresses than %esp?  Like this?

int
main(void)
{
        volatile int *v;
        int a;

        for (v = &a;; v++)
                printf("%p: %#x\n", v, *v);
}

I depends how far you go.  A bunch of stuff is copied out to the top of
the stack by the kernel so you have some slush to work through.  In either
direction you'll eventually get a segfault (sigbus in the above case because
you run into kernel address space).

> 
> Andrew Griffiths
> 
> --
> www.tasmail.com
> 
> 
> 
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