From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753344Ab1AYSLp (ORCPT ); Tue, 25 Jan 2011 13:11:45 -0500 Received: from smtp.outflux.net ([198.145.64.163]:44890 "EHLO smtp.outflux.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752771Ab1AYSLo (ORCPT ); Tue, 25 Jan 2011 13:11:44 -0500 Date: Tue, 25 Jan 2011 10:10:58 -0800 From: Kees Cook To: linux-kernel@vger.kernel.org Cc: Rusty Russell , Tejun Heo , Marcus Meissner , Jason Wessel , Eugene Teo , Andrew Morton , Joe Perches , Bjorn Helgaas , Len Brown , Changli Gao , Dan Rosenberg Subject: [PATCH] use %pK for /proc/kallsyms and /proc/modules Message-ID: <20110125181058.GA25670@outflux.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit Organization: Canonical X-HELO: www.outflux.net Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Instead of messing with permissions on these files, use %pK for kernel addresses to reduce potential information leaks that might be used to help target kernel privilege escalation exploits. Note that this changes %x to %p, so some legitimately 0 values in /proc/kallsyms would have changed from 00000000 to "(null)". To avoid this, "(null)" is not used when using the "K" format. Anything parsing such addresses should have no problem with this change. (Thanks to Joe Perches for the suggestion.) Note that when compiling with -Wformat, these harmless warnings will be emitted, and can be ignored: warning: '0' flag used with ‘%p’ gnu_printf format Signed-off-by: Kees Cook --- kernel/kallsyms.c | 4 ++-- kernel/module.c | 4 ++-- lib/vsprintf.c | 2 +- 3 files changed, 5 insertions(+), 5 deletions(-) diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index 6f6d091..074b762 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -477,11 +477,11 @@ static int s_show(struct seq_file *m, void *p) */ type = iter->exported ? toupper(iter->type) : tolower(iter->type); - seq_printf(m, "%0*lx %c %s\t[%s]\n", + seq_printf(m, "%0*pK %c %s\t[%s]\n", (int)(2 * sizeof(void *)), iter->value, type, iter->name, iter->module_name); } else - seq_printf(m, "%0*lx %c %s\n", + seq_printf(m, "%0*pK %c %s\n", (int)(2 * sizeof(void *)), iter->value, iter->type, iter->name); return 0; diff --git a/kernel/module.c b/kernel/module.c index 34e00b7..748465c 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -1168,7 +1168,7 @@ static ssize_t module_sect_show(struct module_attribute *mattr, { struct module_sect_attr *sattr = container_of(mattr, struct module_sect_attr, mattr); - return sprintf(buf, "0x%lx\n", sattr->address); + return sprintf(buf, "0x%pK\n", sattr->address); } static void free_sect_attrs(struct module_sect_attrs *sect_attrs) @@ -3224,7 +3224,7 @@ static int m_show(struct seq_file *m, void *p) mod->state == MODULE_STATE_COMING ? "Loading": "Live"); /* Used by oprofile and other similar tools. */ - seq_printf(m, " 0x%p", mod->module_core); + seq_printf(m, " 0x%pK", mod->module_core); /* Taints info */ if (mod->taints) diff --git a/lib/vsprintf.c b/lib/vsprintf.c index d3023df..288d770 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -991,7 +991,7 @@ static noinline_for_stack char *pointer(const char *fmt, char *buf, char *end, void *ptr, struct printf_spec spec) { - if (!ptr) { + if (!ptr && *fmt != 'K') { /* * Print (null) with the same width as a pointer so it makes * tabular output look nice. -- 1.7.2.3 -- Kees Cook Ubuntu Security Team