linux-kernel - Is SKAS still required for UML

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-next>] [day] [month] [year] [list]

Message-ID: <alpine.LNX.1.10.0808271251170.1378@fbirervta.pbzchgretzou.qr>
Date:	Wed, 27 Aug 2008 12:57:53 -0400 (EDT)
From:	Jan Engelhardt <jengelh@...ozas.de>
To:	jdike@...ux.intel.com
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Is SKAS still required for UML

Hi,

the UML page at http://user-mode-linux.sourceforge.net/old/skas.html 
mentions that "The UML kernel is present in the address space of each of 
its processes, and, by default, is writeable".

I tried to put this to a test, and actually failed to modify the 
UML kernel/memory image from within it. I had a simple kernel module 
with 'int val = 2;' and upon loading this, done printk("Val is at %p\n", 
&val); to get to know the address. A userspace program inside the UML 
then tried to dereference that address and read the value, but that 
ended in a segfault. /proc/xxx/maps also does not show the UML kernel 
being mapped in any process inside the UML. Note that I was running in 
SKAS0 mode, both host and guest are all 64-bit. Is the NX bit of the 
64-bit platform securing things off, or has SKAS3 become sort of 
obsolete?

Jan
--
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/