From nobody Thu Nov 6 19:05:51 2025 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 1488238485530275.98779954908105; Mon, 27 Feb 2017 15:34:45 -0800 (PST) Received: from localhost ([::1]:57594 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ciUoV-0004B7-UU for importer@patchew.org; Mon, 27 Feb 2017 18:34:43 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47108) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ciUHu-0000iV-Tw for qemu-devel@nongnu.org; Mon, 27 Feb 2017 18:01:06 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ciUHt-0004Aw-Nu for qemu-devel@nongnu.org; Mon, 27 Feb 2017 18:01:03 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:33531 helo=mx0a-001b2d01.pphosted.com) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ciUHt-0004AI-HI for qemu-devel@nongnu.org; Mon, 27 Feb 2017 18:01:01 -0500 Received: from pps.filterd (m0098416.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v1RMra77121469 for ; Mon, 27 Feb 2017 18:01:00 -0500 Received: from e06smtp08.uk.ibm.com (e06smtp08.uk.ibm.com [195.75.94.104]) by mx0b-001b2d01.pphosted.com with ESMTP id 28vn69xy2f-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 27 Feb 2017 18:01:00 -0500 Received: from localhost by e06smtp08.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Mon, 27 Feb 2017 23:00:56 -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 5249C17D8042; Mon, 27 Feb 2017 23:04:09 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (d06av23.portsmouth.uk.ibm.com [9.149.105.59]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v1RN0u9h64749666; Mon, 27 Feb 2017 23:00:56 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A4C91A4051; Mon, 27 Feb 2017 23:00:52 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8A78CA4040; Mon, 27 Feb 2017 23:00:52 +0000 (GMT) Received: from smtp.lab.toulouse-stg.fr.ibm.com (unknown [9.101.4.1]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTP; Mon, 27 Feb 2017 23:00:52 +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 7A7C0220711; Tue, 28 Feb 2017 00:00:55 +0100 (CET) From: Greg Kurz To: qemu-devel@nongnu.org Date: Tue, 28 Feb 2017 00:00:20 +0100 X-Mailer: git-send-email 2.7.4 In-Reply-To: <1488236421-30983-1-git-send-email-groug@kaod.org> References: <1488236421-30983-1-git-send-email-groug@kaod.org> X-TM-AS-GCONF: 00 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 17022723-0032-0000-0000-00000725B494 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17022723-0033-0000-0000-00002394EDD2 Message-Id: <1488236421-30983-31-git-send-email-groug@kaod.org> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2017-02-27_17:, , 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-1702270213 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] [fuzzy] X-Received-From: 148.163.158.5 Subject: [Qemu-devel] [PULL 30/31] 9pfs: local: open2: 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_open2() callback is vulnerable to symlink attacks because it calls: (1) open() 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_open2() 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. Since local_open2() already opens a descriptor to the target file, local_set_cred_passthrough() is modified to reuse it instead of opening a new one. 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 openat(). This partly fixes CVE-2016-9602. Signed-off-by: Greg Kurz Reviewed-by: Stefan Hajnoczi --- hw/9pfs/9p-local.c | 56 ++++++++++++++++++--------------------------------= ---- 1 file changed, 19 insertions(+), 37 deletions(-) diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c index 572eb5886e04..0b8bbf31a12d 100644 --- a/hw/9pfs/9p-local.c +++ b/hw/9pfs/9p-local.c @@ -887,62 +887,45 @@ static int local_fstat(FsContext *fs_ctx, int fid_typ= e, static int local_open2(FsContext *fs_ctx, V9fsPath *dir_path, const char *= name, int flags, FsCred *credp, V9fsFidOpenState *fs) { - char *path; int fd =3D -1; int err =3D -1; - int serrno =3D 0; - V9fsString fullname; - char *buffer =3D NULL; + int dirfd; =20 /* * Mark all the open to not follow symlinks */ flags |=3D O_NOFOLLOW; =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); - fd =3D open(buffer, flags, SM_LOCAL_MODE_BITS); + if (fs_ctx->export_flags & V9FS_SM_MAPPED || + fs_ctx->export_flags & V9FS_SM_MAPPED_FILE) { + fd =3D openat_file(dirfd, name, flags, SM_LOCAL_MODE_BITS); if (fd =3D=3D -1) { - err =3D fd; goto out; } credp->fc_mode =3D credp->fc_mode|S_IFREG; - /* Set cleint credentials in xattr */ - 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); - fd =3D open(buffer, flags, SM_LOCAL_MODE_BITS); - if (fd =3D=3D -1) { - err =3D fd; - goto out; + if (fs_ctx->export_flags & V9FS_SM_MAPPED) { + /* Set cleint credentials in xattr */ + 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_IFREG; - /* Set client credentials in .virtfs_metadata directory files */ - 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); - fd =3D open(buffer, flags, credp->fc_mode); + fd =3D openat_file(dirfd, name, flags, credp->fc_mode); if (fd =3D=3D -1) { - err =3D fd; 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; } } @@ -951,12 +934,11 @@ static int local_open2(FsContext *fs_ctx, V9fsPath *d= ir_path, const char *name, goto out; =20 err_end: - close(fd); - remove(buffer); - errno =3D serrno; + unlinkat_preserve_errno(dirfd, name, + flags & O_DIRECTORY ? AT_REMOVEDIR : 0); + close_preserve_errno(fd); out: - g_free(buffer); - v9fs_string_free(&fullname); + close_preserve_errno(dirfd); return err; } =20 --=20 2.7.4