From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-1521561-1519217830-2-838655259366440222 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, HEADER_FROM_DIFFERENT_DOMAINS 0.001, ME_NOAUTH 0.01, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.132.180.67', Host='vger.kernel.org', Country='CN', FromHeader='org', MailFrom='org' X-Spam-charsets: plain='UTF-8' X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: stable-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1519217829; b=HOXlzMSSMYixd04H7IvpjIgePd5FPwcLTrzMid4pv5+qmUc pu3YuzzPQ/rXNp9yVGgV3XFogBkm9fotCjPii5xSOtv9YT4VvF5XUBcZjGwUlq9q FUiohxiXYiv4l9+3vC71nL12Ia9qc/LPz/hB/KqYUR/m+6X0yoXgXrHlHwzMVVP9 8fZonrhMFP6Zv/wUdL27XnSwTfigUHtqIZo73DHm/czL/MrgrBgH+7TjlOyOns+Q 3YcVBN/QPyPNUjYmhK++FCHIYotLow70VrHvo5g+0dD0KjRdmScOvmmJxrN+LBoD ucquBVrgyFiXsCgWEongCIhGjzOiPEacXQp6jCQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=from:to:cc:subject:date:message-id :in-reply-to:references:mime-version:content-type:sender :list-id; s=arctest; t=1519217829; bh=JpcKYMmXQa9W76v+oLKtF0wnFs Z5oyZJySS0t3+Zp84=; b=lUTUrM0D42LhEM7nBi5lGRLfDylaH8OFXK8mmoqxXf iz3zfHcc+dXctXwOpPxdRnmRjMfgimp6ry7MQ/hCUrLcvBhGKJh7TNNMIXynRJxf 3dTYYXRL1CcMiBP06dPijCr4sb3OGmzVB4+U4e9Y5/TFfIq+MMNerc5HoUDlT2wA bRXHqRoksHcSd9IrtcglaI7JaSYUlP2tTZY0J+Otzaj3Wvb4hgawr3LoWqADHoy1 rBlUngdyh1ekHSaMDjhgIvF1EQAFKRoYYymA4RXtoYVaY4CjaoEEADFK23lxYlqh mihHH7v3qssj9ghwdQ/QObnn6ERI9RFeZNH/xg1bc15A== ARC-Authentication-Results: i=1; mx6.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=linuxfoundation.org; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=linuxfoundation.org header.result=pass header_is_org_domain=yes Authentication-Results: mx6.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=linuxfoundation.org; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=linuxfoundation.org header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934588AbeBUM5G (ORCPT ); Wed, 21 Feb 2018 07:57:06 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:35650 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932701AbeBUM5E (ORCPT ); Wed, 21 Feb 2018 07:57:04 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dmitry Vyukov , Vegard Nossum , Al Viro , Linus Torvalds , Eric Biggers Subject: [PATCH 4.9 68/77] vfs: dont do RCU lookup of empty pathnames Date: Wed, 21 Feb 2018 13:49:17 +0100 Message-Id: <20180221124435.068113114@linuxfoundation.org> X-Mailer: git-send-email 2.16.2 In-Reply-To: <20180221124432.172390020@linuxfoundation.org> References: <20180221124432.172390020@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Linus Torvalds commit c0eb027e5aef70b71e5a38ee3e264dc0b497f343 upstream. Normal pathname lookup doesn't allow empty pathnames, but using AT_EMPTY_PATH (with name_to_handle_at() or fstatat(), for example) you can trigger an empty pathname lookup. And not only is the RCU lookup in that case entirely unnecessary (because we'll obviously immediately finalize the end result), it is actively wrong. Why? An empth path is a special case that will return the original 'dirfd' dentry - and that dentry may not actually be RCU-free'd, resulting in a potential use-after-free if we were to initialize the path lazily under the RCU read lock and depend on complete_walk() finalizing the dentry. Found by syzkaller and KASAN. Reported-by: Dmitry Vyukov Reported-by: Vegard Nossum Acked-by: Al Viro Signed-off-by: Linus Torvalds Cc: Eric Biggers Signed-off-by: Greg Kroah-Hartman --- fs/namei.c | 3 +++ 1 file changed, 3 insertions(+) --- a/fs/namei.c +++ b/fs/namei.c @@ -2138,6 +2138,9 @@ static const char *path_init(struct name int retval = 0; const char *s = nd->name->name; + if (!*s) + flags &= ~LOOKUP_RCU; + nd->last_type = LAST_ROOT; /* if there are only slashes... */ nd->flags = flags | LOOKUP_JUMPED | LOOKUP_PARENT; nd->depth = 0;