From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934196Ab3IDApt (ORCPT ); Tue, 3 Sep 2013 20:45:49 -0400 Received: from tundra.namei.org ([65.99.196.166]:34541 "EHLO tundra.namei.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761445Ab3IDAps (ORCPT ); Tue, 3 Sep 2013 20:45:48 -0400 Date: Wed, 4 Sep 2013 10:47:19 +1000 (EST) From: James Morris To: Matthew Garrett cc: linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org, keescook@chromium.org, hpa@zytor.com Subject: Re: [PATCH V3 06/11] Restrict /dev/mem and /dev/kmem when module loading is restricted In-Reply-To: <1378252218-18798-7-git-send-email-matthew.garrett@nebula.com> Message-ID: References: <1378252218-18798-1-git-send-email-matthew.garrett@nebula.com> <1378252218-18798-7-git-send-email-matthew.garrett@nebula.com> User-Agent: Alpine 2.02 (LRH 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 3 Sep 2013, Matthew Garrett wrote: > Allowing users to write to address space makes it possible for the kernel > to be subverted, avoiding module loading restrictions. Prevent this when > any restrictions have been imposed on loading modules. > > Signed-off-by: Matthew Garrett Reviewed-by: James Morris > --- > drivers/char/mem.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/char/mem.c b/drivers/char/mem.c > index 1af8664..61406c8 100644 > --- a/drivers/char/mem.c > +++ b/drivers/char/mem.c > @@ -159,6 +159,9 @@ static ssize_t write_mem(struct file *file, const char __user *buf, > unsigned long copied; > void *ptr; > > + if (secure_modules()) > + return -EPERM; > + > if (!valid_phys_addr_range(p, count)) > return -EFAULT; > > @@ -497,6 +500,9 @@ static ssize_t write_kmem(struct file *file, const char __user *buf, > char *kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */ > int err = 0; > > + if (secure_modules()) > + return -EPERM; > + > if (p < (unsigned long) high_memory) { > unsigned long to_write = min_t(unsigned long, count, > (unsigned long)high_memory - p); > -- > 1.8.3.1 > > -- > 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/ > -- James Morris