From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756714AbZKERjc (ORCPT ); Thu, 5 Nov 2009 12:39:32 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755207AbZKERjb (ORCPT ); Thu, 5 Nov 2009 12:39:31 -0500 Received: from smtp1.linux-foundation.org ([140.211.169.13]:44122 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755119AbZKERjb (ORCPT ); Thu, 5 Nov 2009 12:39:31 -0500 Date: Thu, 5 Nov 2009 09:38:21 -0800 (PST) From: Linus Torvalds X-X-Sender: torvalds@localhost.localdomain To: Jiri Kosina cc: Michael Gilbert , Michael Buesch , Jack Steiner , linux-kernel@vger.kernel.org, stable@kernel.org Subject: Re: CVE-2009-2584 In-Reply-To: Message-ID: References: <20091104170542.e40b12ec.michael.s.gilbert@gmail.com> User-Agent: Alpine 2.01 (LFD 1184 2008-12-16) 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 Thu, 5 Nov 2009, Linus Torvalds wrote: > > Untested, of course. And since almost nobody has the hardware, so it's not > like it's ever likely to _be_ tested. > > Linus > > --- > drivers/misc/sgi-gru/gruprocfs.c | 4 +++- > 1 files changed, 3 insertions(+), 1 deletions(-) > > diff --git a/drivers/misc/sgi-gru/gruprocfs.c b/drivers/misc/sgi-gru/gruprocfs.c > index ccd4408..c0e17b0 100644 > --- a/drivers/misc/sgi-gru/gruprocfs.c > +++ b/drivers/misc/sgi-gru/gruprocfs.c > @@ -164,7 +164,9 @@ static ssize_t options_write(struct file *file, const char __user *userbuf, > unsigned long val; > char buf[80]; > > - if (strncpy_from_user(buf, userbuf, sizeof(buf) - 1) < 0) > + if (count >= sizeof(buf)) > + count = sizeof(buf)-1; > + if (copy_from_user(buf, userbuf, count)) > return -EFAULT; > buf[count - 1] = '\0'; And it's wrong. That 'count-1' was always wrong. It seems to _depend_ on people doing things like echo number > /proc/.. and the 'echo' adding a '\n' at the end, and then 'buf[count-1] = 0' clearing away the '\n'. Which is pointless, since '\n' at the end is the _one_ thing strict_strtoul() accepts. And it's wrong, because it means that echo -n number > /proc.. fails. In other words, the whole function is utter sh*t as far as I can tell. There's basically not a single correct line in the whole thing. Even the 'strict_strtoul()' line is absolute and utter crap, since it forces decimal numbers, but 'options_show()' will then show it as a hex number (and a hex number is natural, since it's a set of flags). It also doesn't actually return an error if you write some invalid value, and it's totally pointless to have that 'val' temporary, since the strict_strtoul function only writes the result if it is successful _anyway_. The size of the buffer is also insane. Since the _only_ thing we will ever accept is a number, there's no point in allowing all that many characters. And silently ignoring the extra characters kind of makes the whole 'strict' part of 'strict_strtoul()' pointless. So here's a second try. I guess the 'return count/-EFAULT' lines were actually correct after all. So it wasn't _all_ buggy or insane. Still entirely untested. Linus --- drivers/misc/sgi-gru/gruprocfs.c | 13 +++++++------ 1 files changed, 7 insertions(+), 6 deletions(-) diff --git a/drivers/misc/sgi-gru/gruprocfs.c b/drivers/misc/sgi-gru/gruprocfs.c index ccd4408..762f179 100644 --- a/drivers/misc/sgi-gru/gruprocfs.c +++ b/drivers/misc/sgi-gru/gruprocfs.c @@ -161,14 +161,15 @@ static int options_show(struct seq_file *s, void *p) static ssize_t options_write(struct file *file, const char __user *userbuf, size_t count, loff_t *data) { - unsigned long val; - char buf[80]; + char buf[16]; - if (strncpy_from_user(buf, userbuf, sizeof(buf) - 1) < 0) + if (count >= sizeof(buf)) + return -EINVAL; + if (copy_from_user(buf, userbuf, count)) return -EFAULT; - buf[count - 1] = '\0'; - if (!strict_strtoul(buf, 10, &val)) - gru_options = val; + buf[count] = '\0'; + if (strict_strtoul(buf, 0, &gru_options)) + return -EINVAL; return count; }