From patchwork Mon May 11 18:08:02 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Al Viro X-Patchwork-Id: 6380561 Return-Path: X-Original-To: patchwork-linux-fsdevel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id E2167BEEE1 for ; Mon, 11 May 2015 18:12:19 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 1BC07209C2 for ; Mon, 11 May 2015 18:12:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2CCEB209C5 for ; Mon, 11 May 2015 18:12:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932437AbbEKSMM (ORCPT ); Mon, 11 May 2015 14:12:12 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:47597 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755063AbbEKSIa (ORCPT ); Mon, 11 May 2015 14:08:30 -0400 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.76 #1 (Red Hat Linux)) id 1Yrs7w-0001WY-Ip; Mon, 11 May 2015 18:08:28 +0000 From: Al Viro To: Linus Torvalds Cc: Neil Brown , Christoph Hellwig , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH v3 102/110] namei: make may_follow_link() safe in RCU mode Date: Mon, 11 May 2015 19:08:02 +0100 Message-Id: <1431367690-5223-102-git-send-email-viro@ZenIV.linux.org.uk> X-Mailer: git-send-email 1.7.7.6 In-Reply-To: <20150511180650.GA4147@ZenIV.linux.org.uk> References: <20150511180650.GA4147@ZenIV.linux.org.uk> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Al Viro We *can't* call that audit garbage in RCU mode - it's doing a weird mix of allocations (GFP_NOFS, immediately followed by GFP_KERNEL) and I'm not touching that... thing again. So if this security sclero^Whardening feature gets triggered when we are in RCU mode, tough - we'll fail with -ECHILD and have everything restarted in non-RCU mode. Only to hit the same test and fail, this time with EACCES and with (oh, rapture) an audit spew produced. Signed-off-by: Al Viro --- fs/namei.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/namei.c b/fs/namei.c index 998c3c2..20bf494 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -794,6 +794,9 @@ static inline int may_follow_link(struct nameidata *nd) if (uid_eq(parent->i_uid, inode->i_uid)) return 0; + if (nd->flags & LOOKUP_RCU) + return -ECHILD; + audit_log_link_denied("follow_link", &nd->stack[0].link); return -EACCES; }