From nobody Mon Feb 9 23:40:30 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zoho.com; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; Return-Path: Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) by mx.zohomail.com with SMTPS id 1488278540659566.7248926625846; Tue, 28 Feb 2017 02:42:20 -0800 (PST) Received: from localhost ([::1]:60066 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cifEY-0001oG-DD for importer@patchew.org; Tue, 28 Feb 2017 05:42:18 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37864) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cif3x-0001Uy-OF for qemu-devel@nongnu.org; Tue, 28 Feb 2017 05:31:24 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cif3u-00084C-JL for qemu-devel@nongnu.org; Tue, 28 Feb 2017 05:31:21 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:40781) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cif3u-000841-8x for qemu-devel@nongnu.org; Tue, 28 Feb 2017 05:31:18 -0500 Received: from pps.filterd (m0098393.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v1SASdST051648 for ; Tue, 28 Feb 2017 05:31:17 -0500 Received: from e06smtp05.uk.ibm.com (e06smtp05.uk.ibm.com [195.75.94.101]) by mx0a-001b2d01.pphosted.com with ESMTP id 28w3d4jxrp-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Tue, 28 Feb 2017 05:31:16 -0500 Received: from localhost by e06smtp05.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Tue, 28 Feb 2017 10:31:11 -0000 Received: from b06cxnps3075.portsmouth.uk.ibm.com (d06relay10.portsmouth.uk.ibm.com [9.149.109.195]) by d06dlp01.portsmouth.uk.ibm.com (Postfix) with ESMTP id D367817D805F; Tue, 28 Feb 2017 10:34:23 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (mk.ibm.com [9.149.105.60]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v1SAVAKp26935462; Tue, 28 Feb 2017 10:31:10 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 93A3542045; Tue, 28 Feb 2017 10:31:05 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 827AB4204F; Tue, 28 Feb 2017 10:31:05 +0000 (GMT) Received: from smtp.lab.toulouse-stg.fr.ibm.com (unknown [9.101.4.1]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 28 Feb 2017 10:31:05 +0000 (GMT) Received: from bahia.lan (icon-9-164-183-34.megacenter.de.ibm.com [9.164.183.34]) by smtp.lab.toulouse-stg.fr.ibm.com (Postfix) with ESMTP id 6BEF7220748; Tue, 28 Feb 2017 11:31:09 +0100 (CET) From: Greg Kurz To: qemu-devel@nongnu.org Date: Tue, 28 Feb 2017 11:30:38 +0100 X-Mailer: git-send-email 2.7.4 In-Reply-To: <1488277840-18608-1-git-send-email-groug@kaod.org> References: <1488277840-18608-1-git-send-email-groug@kaod.org> X-TM-AS-GCONF: 00 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 17022810-0020-0000-0000-0000027C4214 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17022810-0021-0000-0000-00001F8791D6 Message-Id: <1488277840-18608-27-git-send-email-groug@kaod.org> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2017-02-28_07:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=13 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1612050000 definitions=main-1702280098 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] [fuzzy] X-Received-From: 148.163.156.1 Subject: [Qemu-devel] [PULL 26/28] 9pfs: local: mkdir: don't follow symlinks X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , "Aneesh Kumar K.V" , Greg Kurz Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RSF_0 Z_629925259 SPT_0 Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" The local_mkdir() callback is vulnerable to symlink attacks because it calls: (1) mkdir() which follows symbolic links for all path elements but the rightmost one (2) local_set_xattr()->setxattr() which follows symbolic links for all path elements (3) local_set_mapped_file_attr() which calls in turn local_fopen() and mkdir(), both functions following symbolic links for all path elements but the rightmost one (4) local_post_create_passthrough() which calls in turn lchown() and chmod(), both functions also following symbolic links This patch converts local_mkdir() to rely on opendir_nofollow() and mkdirat() to fix (1), as well as local_set_xattrat(), local_set_mapped_file_attrat() and local_set_cred_passthrough() to fix (2), (3) and (4) respectively. The mapped and mapped-file security modes are supposed to be identical, except for the place where credentials and file modes are stored. While here, we also make that explicit by sharing the call to mkdirat(). This partly fixes CVE-2016-9602. Signed-off-by: Greg Kurz Reviewed-by: Stefan Hajnoczi --- hw/9pfs/9p-local.c | 55 ++++++++++++++++++++------------------------------= ---- 1 file changed, 20 insertions(+), 35 deletions(-) diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c index db70c2daf498..33893d50113c 100644 --- a/hw/9pfs/9p-local.c +++ b/hw/9pfs/9p-local.c @@ -799,62 +799,47 @@ out: static int local_mkdir(FsContext *fs_ctx, V9fsPath *dir_path, const char *name, FsCred *credp) { - char *path; int err =3D -1; - int serrno =3D 0; - V9fsString fullname; - char *buffer =3D NULL; + int dirfd; =20 - v9fs_string_init(&fullname); - v9fs_string_sprintf(&fullname, "%s/%s", dir_path->data, name); - path =3D fullname.data; + dirfd =3D local_opendir_nofollow(fs_ctx, dir_path->data); + if (dirfd =3D=3D -1) { + return -1; + } =20 - /* Determine the security model */ - if (fs_ctx->export_flags & V9FS_SM_MAPPED) { - buffer =3D rpath(fs_ctx, path); - err =3D mkdir(buffer, SM_LOCAL_DIR_MODE_BITS); + if (fs_ctx->export_flags & V9FS_SM_MAPPED || + fs_ctx->export_flags & V9FS_SM_MAPPED_FILE) { + err =3D mkdirat(dirfd, name, SM_LOCAL_DIR_MODE_BITS); if (err =3D=3D -1) { goto out; } - credp->fc_mode =3D credp->fc_mode|S_IFDIR; - err =3D local_set_xattr(buffer, credp); - if (err =3D=3D -1) { - serrno =3D errno; - goto err_end; - } - } else if (fs_ctx->export_flags & V9FS_SM_MAPPED_FILE) { - buffer =3D rpath(fs_ctx, path); - err =3D mkdir(buffer, SM_LOCAL_DIR_MODE_BITS); - if (err =3D=3D -1) { - goto out; + credp->fc_mode =3D credp->fc_mode | S_IFDIR; + + if (fs_ctx->export_flags & V9FS_SM_MAPPED) { + err =3D local_set_xattrat(dirfd, name, credp); + } else { + err =3D local_set_mapped_file_attrat(dirfd, name, credp); } - credp->fc_mode =3D credp->fc_mode|S_IFDIR; - err =3D local_set_mapped_file_attr(fs_ctx, path, credp); if (err =3D=3D -1) { - serrno =3D errno; goto err_end; } - } else if ((fs_ctx->export_flags & V9FS_SM_PASSTHROUGH) || - (fs_ctx->export_flags & V9FS_SM_NONE)) { - buffer =3D rpath(fs_ctx, path); - err =3D mkdir(buffer, credp->fc_mode); + } else if (fs_ctx->export_flags & V9FS_SM_PASSTHROUGH || + fs_ctx->export_flags & V9FS_SM_NONE) { + err =3D mkdirat(dirfd, name, credp->fc_mode); if (err =3D=3D -1) { goto out; } - err =3D local_post_create_passthrough(fs_ctx, path, credp); + err =3D local_set_cred_passthrough(fs_ctx, dirfd, name, credp); if (err =3D=3D -1) { - serrno =3D errno; goto err_end; } } goto out; =20 err_end: - remove(buffer); - errno =3D serrno; + unlinkat_preserve_errno(dirfd, name, AT_REMOVEDIR); out: - g_free(buffer); - v9fs_string_free(&fullname); + close_preserve_errno(dirfd); return err; } =20 --=20 2.7.4