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Message-ID: <alpine.LFD.2.10.1412261914220.28221@wniryva.cad.erqung.pbz>
Date: Fri, 26 Dec 2014 19:19:27 +0530 (IST)
From: P J P <ppandit@...hat.com>
To: oss security list <oss-security@...ts.openwall.com>
cc: Andy Lutomirski <luto@...capital.net>
Subject: Re: CVE Request: Linux x86_64 userspace address
leak
+-- On Thu, 18 Dec 2014, Andy Lutomirski wrote --+
| On all* Linux x86_64 kernels, malicious user programs can learn the
| TLS base addresses of threads** that they preempt.
|
| In principle, this bug will allow programs to partially bypass ASLR
| when attacking other user programs. Figuring out how to adapt the
| test code to do that is left as an exercise to the reader.
|
| https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/arch/x86?id=f647d7c155f069c1a068030255c300663516420e
|
| ** The attack won't work against 64-bit threads with TLS bases > 4GB,
| but AFAIK that's unusual.
It seems to require 32bit interfaces(CONFIG_X86_32). On x86_64 Fedora/RHEL
kernels, it says:
===
$ cat /etc/redhat-release
Fedora release 21 (Twenty One)
$
$ cc -xc -o estest estest.c
$ cc -xc -o gsbasetest gsbasetest.c
$
$ ./estest
estest: set_thread_area: Function not implemented
$
$ ./gsbasetest
[OK] ARCH_SET_GS worked
[OK] Writing 0 to gs worked
[FAIL] gsbase was corrupted
$
===
--
Prasad J Pandit / Red Hat Product Security Team
47AF CE69 3A90 54AA 9045 1053 DD13 3D32 FE5B 041F
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