From nobody Tue Feb 10 05:41:23 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 148760396383523.149109833539114; Mon, 20 Feb 2017 07:19:23 -0800 (PST) Received: from localhost ([::1]:39129 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cfpkG-0007Gp-Vd for importer@patchew.org; Mon, 20 Feb 2017 10:19:21 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54669) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cfpAj-0008PE-Tx for qemu-devel@nongnu.org; Mon, 20 Feb 2017 09:42:38 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cfpAg-00041f-O2 for qemu-devel@nongnu.org; Mon, 20 Feb 2017 09:42:38 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:49752) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cfpAg-00041X-EN for qemu-devel@nongnu.org; Mon, 20 Feb 2017 09:42:34 -0500 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 v1KEgXT1092927 for ; Mon, 20 Feb 2017 09:42:33 -0500 Received: from e38.co.us.ibm.com (e38.co.us.ibm.com [32.97.110.159]) by mx0a-001b2d01.pphosted.com with ESMTP id 28pnxqka17-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 20 Feb 2017 09:42:33 -0500 Received: from localhost by e38.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Mon, 20 Feb 2017 07:42:30 -0700 Received: from b01cxnp23032.gho.pok.ibm.com (b01cxnp23032.gho.pok.ibm.com [9.57.198.27]) by d03dlp03.boulder.ibm.com (Postfix) with ESMTP id A906E3B2000A; Mon, 20 Feb 2017 07:41:41 -0700 (MST) Received: from b01ledav006.gho.pok.ibm.com (b01ledav006.gho.pok.ibm.com [9.57.199.111]) by b01cxnp23032.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v1KEgSu316449544; Mon, 20 Feb 2017 14:42:28 GMT Received: from b01ledav006.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D5158AC040; Mon, 20 Feb 2017 09:42:26 -0500 (EST) Received: from bahia.lan (unknown [9.164.137.25]) by b01ledav006.gho.pok.ibm.com (Postfix) with ESMTP id 9750EAC048; Mon, 20 Feb 2017 09:42:25 -0500 (EST) From: Greg Kurz To: qemu-devel@nongnu.org Date: Mon, 20 Feb 2017 15:42:26 +0100 In-Reply-To: <148760155821.31154.13876757160410915057.stgit@bahia.lan> References: <148760155821.31154.13876757160410915057.stgit@bahia.lan> User-Agent: StGit/0.17.1-20-gc0b1b-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 17022014-0028-0000-0000-00000717A2BA X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00006651; HX=3.00000240; KW=3.00000007; PH=3.00000004; SC=3.00000204; SDB=6.00824569; UDB=6.00403651; IPR=6.00602025; BA=6.00005157; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00014359; XFM=3.00000011; UTC=2017-02-20 14:42:32 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17022014-0029-0000-0000-000033B87BD1 Message-Id: <148760174673.31154.11366007991909627456.stgit@bahia.lan> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2017-02-20_13:, , 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=8.0.1-1612050000 definitions=main-1702200144 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 24/29] 9pfs: local: chown: 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: Jann Horn , Prasad J Pandit , Greg Kurz , "Aneesh Kumar K.V" , Stefan Hajnoczi Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RSF_0 Z_629925259 SPT_0 The local_chown() callback is vulnerable to symlink attacks because it calls: (1) lchown() 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 This patch converts local_chown() to rely on open_nofollow() and fchownat() to fix (1), as well as local_set_xattrat() and local_set_mapped_file_attrat() to fix (2) and (3) respectively. This partly fixes CVE-2016-9602. Signed-off-by: Greg Kurz Reviewed-by: Stefan Hajnoczi --- hw/9pfs/9p-local.c | 26 +++++++++++++++++--------- 1 file changed, 17 insertions(+), 9 deletions(-) diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c index 56d7731f7ce1..7f1e105d72aa 100644 --- a/hw/9pfs/9p-local.c +++ b/hw/9pfs/9p-local.c @@ -1138,23 +1138,31 @@ static int local_truncate(FsContext *ctx, V9fsPath = *fs_path, off_t size) =20 static int local_chown(FsContext *fs_ctx, V9fsPath *fs_path, FsCred *credp) { - char *buffer; + char *dirpath =3D g_path_get_dirname(fs_path->data); + char *name =3D g_path_get_basename(fs_path->data); int ret =3D -1; - char *path =3D fs_path->data; + int dirfd; + + dirfd =3D local_opendir_nofollow(fs_ctx, dirpath); + if (dirfd =3D=3D -1) { + goto out; + } =20 if ((credp->fc_uid =3D=3D -1 && credp->fc_gid =3D=3D -1) || (fs_ctx->export_flags & V9FS_SM_PASSTHROUGH) || (fs_ctx->export_flags & V9FS_SM_NONE)) { - buffer =3D rpath(fs_ctx, path); - ret =3D lchown(buffer, credp->fc_uid, credp->fc_gid); - g_free(buffer); + ret =3D fchownat(dirfd, name, credp->fc_uid, credp->fc_gid, + AT_SYMLINK_NOFOLLOW); } else if (fs_ctx->export_flags & V9FS_SM_MAPPED) { - buffer =3D rpath(fs_ctx, path); - ret =3D local_set_xattr(buffer, credp); - g_free(buffer); + ret =3D local_set_xattrat(dirfd, name, credp); } else if (fs_ctx->export_flags & V9FS_SM_MAPPED_FILE) { - return local_set_mapped_file_attr(fs_ctx, path, credp); + ret =3D local_set_mapped_file_attrat(dirfd, name, credp); } + + close_preserve_errno(dirfd); +out: + g_free(name); + g_free(dirpath); return ret; } =20