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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1170237588.2865.2.camel@laptopd505.fenrus.org>
Date:	Wed, 31 Jan 2007 17:59:48 +0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	Samium Gromoff <_deepfire@...lingofgreen.ru>
Cc:	Pavel Machek <pavel@....cz>, Valdis.Kletnieks@...edu,
	David Wagner <daw@...berkeley.edu>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Undo some of the pseudo-security madness

> No amount of carefulness will prevent vendors stick arbitrarily
> damaging values of stack and mmap base randomisation, severely reducing
> the usefullness of MAP_FIXED.

MAP_FIXED is useful still. The only safe way is to use addresses you got
from mmap(), eg you overmap something.
Anything else is madness, with or without randomization. The C library
for example is free, and does, allocate memory and stacks etc etc.

Same for many other libraries; in addition libraries change in size all
the time... MAP_FIXED of an address you don't KNOW is free is a bug.
Period.
(using an address previously obtained from mmap() is safest, but you
could in theory also parse /proc/self/maps, although that is racey,
since nothing guarantees that the C library didn't spawn a background
thread that allocates memory)

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/