linux-kernel - Re: revert PIE randomization?

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Message-Id: <1168123332.24110.41.camel@shinybook.infradead.org>
Date:	Sun, 07 Jan 2007 06:42:12 +0800
From:	David Woodhouse <dwmw2@...radead.org>
To:	Hugh Dickins <hugh@...itas.com>
Cc:	Andrew Morton <akpm@...l.org>, Linus Torvalds <torvalds@...l.org>,
	Marcus Meissner <meissner@...e.de>, Andi Kleen <ak@...e.de>,
	Ingo Molnar <mingo@...e.hu>,
	Dave Jones <davej@...emonkey.org.uk>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	linux-kernel@...r.kernel.org
Subject: Re: revert PIE randomization?

On Sat, 2007-01-06 at 20:11 +0000, Hugh Dickins wrote:
> And I notice that Andi added a personality & ADDR_NO_RANDOMIZE check
> into randomize_stack_top: I cannot see why that's necessary there,
> but if it is, then should the ET_DYN case add it too?)

While I think of it... it seems that ADDR_NO_RANDOMIZE isn't "inherited"
across exec of 32-bit binaries on x86_64 or ppc64. The personality flags
get wiped out when we detect a 32-bit ELF executable and set the
personality to PER_LINUX32.

This causes suboptimal behaviour from userspace code which checks
whether it can set ADDR_NO_RANDOMIZE with a sys_personality() call, and
if so re-execs itself. Run on x86_64 or ppc64, these go into an endless
loop because it always gets cleared in the exec.

I've seen such code in two places recently (Macaulay2 and sbcl, iirc).

-- 
dwmw2

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