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Re: non-executable stack (via PT_GNU_STACK) not being enforced

Thanks, Kees.

nx is in /proc/cpuinfo as a flag, though it does not appear at all in my dmesg output.  From what I can tell from the Ubuntu link you supplied, I am assuming this means that my CPU supports nx but I do not have the right type of kernel, i.e., one that uses PAE addressing, to support enforcement (or is that part Ubuntu specific).  Does this sound plausible?

-----Original Message-----
From: Kees Cook <kees@debian.org>
To: Brchk05 <brchk05@aim.com>
Cc: debian-security@lists.debian.org
Sent: Sun, Oct 10, 2010 12:07 pm
Subject: Re: non-executable stack (via PT_GNU_STACK) not being enforced


On Sun, Oct 10, 2010 at 09:53:40AM -0400, Brchk05 wrote:
> However, I am able to inject and execute shellcode from a stack local 
character buffer in both versions.  Is there another system option I am unaware 
of that affects enforcement?  Is enforcement not supported for my system 

Your CPU may not support NX enforcement. Check your dmesg output, and your
cpuflags line in /proc/cpuinfo for "nx".

See https://wiki.ubuntu.com/Security/Features#nx though ignore the nx-emu
notes, as that's not in Debian.


Kees Cook                                            @debian.org

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