From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 39248C282DA for ; Wed, 17 Apr 2019 13:44:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1554021773 for ; Wed, 17 Apr 2019 13:44:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732290AbfDQNoe (ORCPT ); Wed, 17 Apr 2019 09:44:34 -0400 Received: from mail.kernel.org ([198.145.29.99]:47112 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729395AbfDQNoe (ORCPT ); Wed, 17 Apr 2019 09:44:34 -0400 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4C1B220872; Wed, 17 Apr 2019 13:44:32 +0000 (UTC) Date: Wed, 17 Apr 2019 09:44:30 -0400 From: Steven Rostedt To: Petr Mladek Cc: Andy Shevchenko , Rasmus Villemoes , Linus Torvalds , "Tobin C . Harding" , Joe Perches , Andrew Morton , Michal Hocko , Sergey Senozhatsky , Sergey Senozhatsky , linux-kernel@vger.kernel.org, Kees Cook Subject: Re: [PATCH v7 02/10] vsprintf: Consistent %pK handling for kptr_restrict == 0 Message-ID: <20190417094430.6a490eee@gandalf.local.home> In-Reply-To: <20190417115350.20479-3-pmladek@suse.com> References: <20190417115350.20479-1-pmladek@suse.com> <20190417115350.20479-3-pmladek@suse.com> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 17 Apr 2019 13:53:42 +0200 Petr Mladek wrote: > restricted_pointer() pretends that it prints the address when kptr_restrict > is set to zero. But it is never called in this situation. Instead, > pointer() falls back to ptr_to_id() and hashes the pointer. > > This patch removes the potential confusion. klp_restrict is checked only > in restricted_pointer(). > > It actually fixes a small race when the address might get printed unhashed: > > CPU0 CPU1 > > pointer() > if (!kptr_restrict) > /* for example set to 2 */ > restricted_pointer() > /* echo 0 >/proc/sys/kernel/kptr_restrict */ > proc_dointvec_minmax_sysadmin() > klpr_restrict = 0; > switch(kptr_restrict) > case 0: > break: > > number() > > Fixes: commit ef0010a30935de4e0211 ("vsprintf: don't use 'restricted_pointer()' when not restricting") > Cc: Linus Torvalds > Cc: Tobin Harding > Cc: Kees Cook > Signed-off-by: Petr Mladek > Reviewed-by: Andy Shevchenko Reviewed-by: Steven Rostedt (VMware) -- Steve > --- > lib/vsprintf.c | 6 ++---- > 1 file changed, 2 insertions(+), 4 deletions(-) > > diff --git a/lib/vsprintf.c b/lib/vsprintf.c > index eb7b4a06e1f0..2af48948a973 100644 > --- a/lib/vsprintf.c > +++ b/lib/vsprintf.c > @@ -725,8 +725,8 @@ char *restricted_pointer(char *buf, char *end, const void *ptr, > { > switch (kptr_restrict) { > case 0: > - /* Always print %pK values */ > - break; > + /* Handle as %p, hash and do _not_ leak addresses. */ > + return ptr_to_id(buf, end, ptr, spec); > case 1: { > const struct cred *cred; > > @@ -2041,8 +2041,6 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr, > return buf; > } > case 'K': > - if (!kptr_restrict) > - break; > return restricted_pointer(buf, end, ptr, spec); > case 'N': > return netdev_bits(buf, end, ptr, spec, fmt);