From nobody Sun Feb 8 19:55:35 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 149005203088824.24918081804708; Mon, 20 Mar 2017 16:20:30 -0700 (PDT) Received: from localhost ([::1]:35521 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cq6bE-0001YP-49 for importer@patchew.org; Mon, 20 Mar 2017 19:20:29 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40668) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cq6Qc-0001aJ-Pu for qemu-devel@nongnu.org; Mon, 20 Mar 2017 19:09:36 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cq6QY-0004qE-8q for qemu-devel@nongnu.org; Mon, 20 Mar 2017 19:09:30 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:44480) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cq6QX-0004oi-Po for qemu-devel@nongnu.org; Mon, 20 Mar 2017 19:09:26 -0400 Received: from pps.filterd (m0098409.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v2KN8YuW109702 for ; Mon, 20 Mar 2017 19:09:24 -0400 Received: from e15.ny.us.ibm.com (e15.ny.us.ibm.com [129.33.205.205]) by mx0a-001b2d01.pphosted.com with ESMTP id 29ak40pby4-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 20 Mar 2017 19:09:24 -0400 Received: from localhost by e15.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Mon, 20 Mar 2017 19:09:21 -0400 Received: from b01ledav002.gho.pok.ibm.com (b01ledav002.gho.pok.ibm.com [9.57.199.107]) by b01cxnp23032.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v2KN9LPG40435902; Mon, 20 Mar 2017 23:09:21 GMT Received: from b01ledav002.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1646112403D; Mon, 20 Mar 2017 19:09:17 -0400 (EDT) Received: from localhost (unknown [9.53.92.194]) by b01ledav002.gho.pok.ibm.com (Postfix) with ESMTP id EF62B124037; Mon, 20 Mar 2017 19:09:16 -0400 (EDT) From: Michael Roth To: qemu-devel@nongnu.org Date: Mon, 20 Mar 2017 18:07:49 -0500 X-Mailer: git-send-email 2.7.4 In-Reply-To: <1490051325-3770-1-git-send-email-mdroth@linux.vnet.ibm.com> References: <1490051325-3770-1-git-send-email-mdroth@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 17032023-0036-0000-0000-000001B88DAC X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00006819; HX=3.00000240; KW=3.00000007; PH=3.00000004; SC=3.00000206; SDB=6.00836553; UDB=6.00411161; IPR=6.00614321; BA=6.00005224; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00014732; XFM=3.00000013; UTC=2017-03-20 23:09:22 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17032023-0037-0000-0000-00003F0DBB60 Message-Id: <1490051325-3770-26-git-send-email-mdroth@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2017-03-20_16:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=3 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1702020001 definitions=main-1703200196 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] [fuzzy] X-Received-From: 148.163.156.1 Subject: [Qemu-devel] [PATCH 25/81] 9pfs: local: mknod: 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: Greg Kurz , qemu-stable@nongnu.org, 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" From: Greg Kurz The local_mknod() callback is vulnerable to symlink attacks because it calls: (1) mknod() 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_mknod() to rely on opendir_nofollow() and mknodat() to fix (1), as well as local_set_xattrat() and local_set_mapped_file_attrat() to fix (2) and (3) respectively. A new local_set_cred_passthrough() helper based on fchownat() and fchmodat_nofollow() is introduced as a replacement to local_post_create_passthrough() to fix (4). 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 mknodat(). This partly fixes CVE-2016-9602. Signed-off-by: Greg Kurz Reviewed-by: Stefan Hajnoczi (cherry picked from commit d815e7219036d6911fce12efe3e59906264c8536) Signed-off-by: Greg Kurz Signed-off-by: Michael Roth --- hw/9pfs/9p-local.c | 68 ++++++++++++++++++++++++++++----------------------= ---- 1 file changed, 35 insertions(+), 33 deletions(-) diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c index 2bb77e2..f71cc11 100644 --- a/hw/9pfs/9p-local.c +++ b/hw/9pfs/9p-local.c @@ -543,6 +543,23 @@ err: return -1; } =20 +static int local_set_cred_passthrough(FsContext *fs_ctx, int dirfd, + const char *name, FsCred *credp) +{ + if (fchownat(dirfd, name, credp->fc_uid, credp->fc_gid, + AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH) < 0) { + /* + * If we fail to change ownership and if we are + * using security model none. Ignore the error + */ + if ((fs_ctx->export_flags & V9FS_SEC_MASK) !=3D V9FS_SM_NONE) { + return -1; + } + } + + return fchmodat_nofollow(dirfd, name, credp->fc_mode & 07777); +} + static ssize_t local_readlink(FsContext *fs_ctx, V9fsPath *fs_path, char *buf, size_t bufsz) { @@ -737,61 +754,46 @@ out: static int local_mknod(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 mknod(buffer, SM_LOCAL_MODE_BITS|S_IFREG, 0); + if (fs_ctx->export_flags & V9FS_SM_MAPPED || + fs_ctx->export_flags & V9FS_SM_MAPPED_FILE) { + err =3D mknodat(dirfd, name, SM_LOCAL_MODE_BITS | S_IFREG, 0); if (err =3D=3D -1) { goto out; } - 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) { =20 - buffer =3D rpath(fs_ctx, path); - err =3D mknod(buffer, SM_LOCAL_MODE_BITS|S_IFREG, 0); - if (err =3D=3D -1) { - goto out; + 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); } - 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 mknod(buffer, credp->fc_mode, credp->fc_rdev); + } else if (fs_ctx->export_flags & V9FS_SM_PASSTHROUGH || + fs_ctx->export_flags & V9FS_SM_NONE) { + err =3D mknodat(dirfd, name, credp->fc_mode, credp->fc_rdev); 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, 0); out: - g_free(buffer); - v9fs_string_free(&fullname); + close_preserve_errno(dirfd); return err; } =20 --=20 2.7.4