Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933274AbaBEUpd (ORCPT ); Wed, 5 Feb 2014 15:45:33 -0500 Received: from mail1.windriver.com ([147.11.146.13]:48298 "EHLO mail1.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754871AbaBEUGU (ORCPT ); Wed, 5 Feb 2014 15:06:20 -0500 From: Paul Gortmaker To: , CC: Alan Cox , Linus Torvalds , Andrew Morton , Peter Zijlstra , Ingo Molnar , Paul Gortmaker Subject: [v2.6.34-stable 109/213] x86/msr: Add capabilities check Date: Wed, 5 Feb 2014 15:01:04 -0500 Message-ID: <1391630568-49251-110-git-send-email-paul.gortmaker@windriver.com> X-Mailer: git-send-email 1.8.5.2 In-Reply-To: <1391630568-49251-1-git-send-email-paul.gortmaker@windriver.com> References: <1391630568-49251-1-git-send-email-paul.gortmaker@windriver.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Alan Cox ------------------- This is a commit scheduled for the next v2.6.34 longterm release. http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git If you see a problem with using this for longterm, please comment. ------------------- commit c903f0456bc69176912dee6dd25c6a66ee1aed00 upstream. At the moment the MSR driver only relies upon file system checks. This means that anything as root with any capability set can write to MSRs. Historically that wasn't very interesting but on modern processors the MSRs are such that writing to them provides several ways to execute arbitary code in kernel space. Sample code and documentation on doing this is circulating and MSR attacks are used on Windows 64bit rootkits already. In the Linux case you still need to be able to open the device file so the impact is fairly limited and reduces the security of some capability and security model based systems down towards that of a generic "root owns the box" setup. Therefore they should require CAP_SYS_RAWIO to prevent an elevation of capabilities. The impact of this is fairly minimal on most setups because they don't have heavy use of capabilities. Those using SELinux, SMACK or AppArmor rules might want to consider if their rulesets on the MSR driver could be tighter. Signed-off-by: Alan Cox Cc: Linus Torvalds Cc: Andrew Morton Cc: Peter Zijlstra Signed-off-by: Ingo Molnar Signed-off-by: Paul Gortmaker --- arch/x86/kernel/msr.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c index 4d4468e9f47c..56b77410a9fe 100644 --- a/arch/x86/kernel/msr.c +++ b/arch/x86/kernel/msr.c @@ -176,6 +176,9 @@ static int msr_open(struct inode *inode, struct file *file) unsigned int cpu; struct cpuinfo_x86 *c; + if (!capable(CAP_SYS_RAWIO)) + return -EPERM; + cpu = iminor(file->f_path.dentry->d_inode); if (cpu >= nr_cpu_ids || !cpu_online(cpu)) return -ENXIO; /* No such CPU */ -- 1.8.5.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/