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Re: CVE request: kernel: proc: clean up and fix /proc/<pid>/mem handling
From: "Jason A. Donenfeld" <Jason () zx2c4 com>
Date: Sun, 22 Jan 2012 20:47:02 +0100

On Sun, Jan 22, 2012 at 20:43, Solar Designer <solar () openwall com> wrote:
On Sun, Jan 22, 2012 at 07:30:53PM +0100, Jason A. Donenfeld wrote:
The issue is described in detail here: http://blog.zx2c4.com/749

Thanks!  This explains the self_exec_id issue and one attack on it.

Why are you not posting this to oss-security yet?  Do you feel that your
blog receives less exposure and you don't want to expose this additional
detail on the attack to a wider audience until there are distro vendor
updates?

No, I just didn't want to blog-spam a rather well focused mailing list
:-). I'll cc oss-security on this email though.



BTW, self_exec_id was originally introduced into the kernel 10+ years
ago with some involvement from me, and for a significantly different
purpose (protecting changed parent against malicious child death signals).
I think its use for /proc/pid/mem was introduced last year (2011).

Any comments on the fix?

http://git.kernel.org/linus/e268337dfe26dfc7efd422a804dbb27977a3cccc

My primary concern was that the first might be broken.  I have some
further thoughts on this since I posted, though.  I'll post an update.

I'm not sure yet; I haven't looked at it carefully. First instinct is
that there's
[ old process { old & new ] new process}
overlapping as a possibility, but I really have no idea. I'll take a
closer look soon.


Alexander


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