From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751930AbdJTGoE (ORCPT ); Fri, 20 Oct 2017 02:44:04 -0400 Received: from smtp.nue.novell.com ([195.135.221.5]:38832 "EHLO smtp.nue.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751019AbdJTGoC (ORCPT ); Fri, 20 Oct 2017 02:44:02 -0400 Date: Fri, 20 Oct 2017 14:43:49 +0800 From: joeyli To: David Howells Cc: linux-security-module@vger.kernel.org, gnomes@lxorguk.ukuu.org.uk, linux-efi@vger.kernel.org, matthew.garrett@nebula.com, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, jforbes@redhat.com Subject: Re: [PATCH 12/27] x86/msr: Restrict MSR access when the kernel is locked down Message-ID: <20171020064349.GT3285@linux-l9pv.suse> References: <150842463163.7923.11081723749106843698.stgit@warthog.procyon.org.uk> <150842472452.7923.2592278090192179002.stgit@warthog.procyon.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <150842472452.7923.2592278090192179002.stgit@warthog.procyon.org.uk> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Archived-At: List-Archive: List-Post: On Thu, Oct 19, 2017 at 03:52:04PM +0100, David Howells wrote: > From: Matthew Garrett > > Writing to MSRs should not be allowed if the kernel is locked down, since > it could lead to execution of arbitrary code in kernel mode. Based on a > patch by Kees Cook. > > Signed-off-by: Matthew Garrett > Signed-off-by: David Howells > Acked-by: Kees Cook > Reviewed-by: Thomas Gleixner I have reviewed this patch. Please feel free to add: Reviewed-by: "Lee, Chun-Yi" Thanks! Joey Lee > cc: x86@kernel.org > --- > > arch/x86/kernel/msr.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c > index ef688804f80d..a05a97863286 100644 > --- a/arch/x86/kernel/msr.c > +++ b/arch/x86/kernel/msr.c > @@ -84,6 +84,9 @@ static ssize_t msr_write(struct file *file, const char __user *buf, > int err = 0; > ssize_t bytes = 0; > > + if (kernel_is_locked_down("Direct MSR access")) > + return -EPERM; > + > if (count % 8) > return -EINVAL; /* Invalid chunk size */ > > @@ -131,6 +134,10 @@ static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg) > err = -EBADF; > break; > } > + if (kernel_is_locked_down("Direct MSR access")) { > + err = -EPERM; > + break; > + } > if (copy_from_user(®s, uregs, sizeof regs)) { > err = -EFAULT; > break; > > -- > To unsubscribe from this list: send the line "unsubscribe linux-efi" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html