linux-kernel - [PATCH] Undo some of the pseudo-security madness

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Date:	Sat, 20 Jan 2007 17:37:22 +0300
From:	Samium Gromoff <_deepfire@...lingofgreen.ru>
To:	linux-kernel@...r.kernel.org
Subject: [PATCH] Undo some of the pseudo-security madness

This patch removes the dropping of ADDR_NO_RANDOMIZE upon execution of setuid
binaries.

Why? The answer consists of two parts:

Firstly, there are valid applications which need an unadulterated memory map.
Some of those which do their memory management, like lisp systems (like SBCL).
They try to achieve this by setting ADDR_NO_RANDOMIZE and reexecuting themselves.

Secondly, there also are valid reasons to want those applications to be setuid
root. Like poking hardware.

So, here we have a buffer-overflow protection technique, which does not
actually protect against buffer overflows[1], breaking valid applications.

I suggest getting rid of it.

--- include/linux/personality.h	2007-01-20 17:31:01.000000000 +0300
+++ include/linux-sane/personality.h	2007-01-20 17:32:50.000000000 +0300
@@ -40,7 +40,7 @@
  * Security-relevant compatibility flags that must be
  * cleared upon setuid or setgid exec:
  */
-#define PER_CLEAR_ON_SETID (READ_IMPLIES_EXEC|ADDR_NO_RANDOMIZE)
+#define PER_CLEAR_ON_SETID (READ_IMPLIES_EXEC)

 /*
  * Personality types.

Signed-off-by: Samium Gromoff <_deepfire@...linfofgreen.ru>

[1]. See the excellent, 'Hackers Hut' by Andries Brouwer, which describes
how AS randomisation can be got around by the means of linux-gate.so.1
-
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