From nobody Tue Feb 10 07:22:30 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 1487602870222837.7980079949787; Mon, 20 Feb 2017 07:01:10 -0800 (PST) Received: from localhost ([::1]:39034 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cfpSd-0007gX-OX for importer@patchew.org; Mon, 20 Feb 2017 10:01:07 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54598) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cfpAW-0008Am-8y for qemu-devel@nongnu.org; Mon, 20 Feb 2017 09:42:27 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cfpAT-0003zs-3b for qemu-devel@nongnu.org; Mon, 20 Feb 2017 09:42:24 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:53444 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 1cfpAS-0003zj-St for qemu-devel@nongnu.org; Mon, 20 Feb 2017 09:42:21 -0500 Received: from pps.filterd (m0098417.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v1KEd0m2034984 for ; Mon, 20 Feb 2017 09:42:20 -0500 Received: from e35.co.us.ibm.com (e35.co.us.ibm.com [32.97.110.153]) by mx0a-001b2d01.pphosted.com with ESMTP id 28r00g6w1e-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 20 Feb 2017 09:42:19 -0500 Received: from localhost by e35.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Mon, 20 Feb 2017 07:42:15 -0700 Received: from b01cxnp22034.gho.pok.ibm.com (b01cxnp22034.gho.pok.ibm.com [9.57.198.24]) by d03dlp03.boulder.ibm.com (Postfix) with ESMTP id C8AD119D8026; Mon, 20 Feb 2017 07:41:26 -0700 (MST) Received: from b01ledav004.gho.pok.ibm.com (b01ledav004.gho.pok.ibm.com [9.57.199.109]) by b01cxnp22034.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v1KEgE2541156674; Mon, 20 Feb 2017 14:42:14 GMT Received: from b01ledav004.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 59010112047; Mon, 20 Feb 2017 09:42:13 -0500 (EST) Received: from bahia.lan (unknown [9.164.137.25]) by b01ledav004.gho.pok.ibm.com (Postfix) with ESMTP id 21CC611204B; Mon, 20 Feb 2017 09:42:11 -0500 (EST) From: Greg Kurz To: qemu-devel@nongnu.org Date: Mon, 20 Feb 2017 15:42:11 +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: 17022014-0012-0000-0000-000013B54F2C 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=6.00602024; 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 14:42:17 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17022014-0013-0000-0000-00004B92B95D Message-Id: <148760173178.31154.10880735541217141085.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: 148.163.158.5 Subject: [Qemu-devel] [PATCH 22/29] 9pfs: local: link: 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_link() callback is vulnerable to symlink attacks because it calls: (1) link() which follows symbolic links for all path elements but the rightmost one (2) local_create_mapped_attr_dir()->mkdir() which follows symbolic links for all path elements but the rightmost one This patch converts local_link() to rely on opendir_nofollow() and linkat() to fix (1), mkdirat() to fix (2). This partly fixes CVE-2016-9602. Signed-off-by: Greg Kurz Reviewed-by: Stefan Hajnoczi --- hw/9pfs/9p-local.c | 86 ++++++++++++++++++++++++++++++++++--------------= ---- 1 file changed, 57 insertions(+), 29 deletions(-) diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c index 9b9c39ee42ee..fb536fdb3082 100644 --- a/hw/9pfs/9p-local.c +++ b/hw/9pfs/9p-local.c @@ -69,6 +69,13 @@ static void renameat_preserve_errno(int odirfd, const ch= ar *opath, int ndirfd, errno =3D serrno; } =20 +static void unlinkat_preserve_errno(int dirfd, const char *path, int flags) +{ + int serrno =3D errno; + unlinkat(dirfd, path, flags); + errno =3D serrno; +} + #define VIRTFS_META_DIR ".virtfs_metadata" =20 static char *local_mapped_attr_path(FsContext *ctx, const char *path) @@ -912,49 +919,70 @@ out: static int local_link(FsContext *ctx, V9fsPath *oldpath, V9fsPath *dirpath, const char *name) { - int ret; - V9fsString newpath; - char *buffer, *buffer1; - int serrno; + char *odirpath =3D g_path_get_dirname(oldpath->data); + char *oname =3D g_path_get_basename(oldpath->data); + int ret =3D -1; + int odirfd, ndirfd; =20 - v9fs_string_init(&newpath); - v9fs_string_sprintf(&newpath, "%s/%s", dirpath->data, name); + odirfd =3D local_opendir_nofollow(ctx, odirpath); + if (odirfd =3D=3D -1) { + goto out; + } =20 - buffer =3D rpath(ctx, oldpath->data); - buffer1 =3D rpath(ctx, newpath.data); - ret =3D link(buffer, buffer1); - g_free(buffer); - if (ret < 0) { + ndirfd =3D local_opendir_nofollow(ctx, dirpath->data); + if (ndirfd =3D=3D -1) { + close_preserve_errno(odirfd); goto out; } =20 + ret =3D linkat(odirfd, oname, ndirfd, name, 0); + if (ret < 0) { + goto out_close; + } + /* now link the virtfs_metadata files */ if (ctx->export_flags & V9FS_SM_MAPPED_FILE) { - char *vbuffer, *vbuffer1; + int omap_dirfd, nmap_dirfd; =20 - /* Link the .virtfs_metadata files. Create the metada directory */ - ret =3D local_create_mapped_attr_dir(ctx, newpath.data); - if (ret < 0) { - goto err_out; + ret =3D mkdirat(ndirfd, VIRTFS_META_DIR, 0700); + if (ret < 0 && errno !=3D EEXIST) { + goto err_undo_link; } - vbuffer =3D local_mapped_attr_path(ctx, oldpath->data); - vbuffer1 =3D local_mapped_attr_path(ctx, newpath.data); - ret =3D link(vbuffer, vbuffer1); - g_free(vbuffer); - g_free(vbuffer1); + + omap_dirfd =3D openat(odirfd, VIRTFS_META_DIR, + O_RDONLY | O_DIRECTORY | O_NOFOLLOW); + if (omap_dirfd =3D=3D -1) { + goto err; + } + + nmap_dirfd =3D openat(ndirfd, VIRTFS_META_DIR, + O_RDONLY | O_DIRECTORY | O_NOFOLLOW); + if (nmap_dirfd =3D=3D -1) { + close_preserve_errno(omap_dirfd); + goto err; + } + + ret =3D linkat(omap_dirfd, oname, nmap_dirfd, name, 0); + close_preserve_errno(nmap_dirfd); + close_preserve_errno(omap_dirfd); if (ret < 0 && errno !=3D ENOENT) { - goto err_out; + goto err_undo_link; } + + ret =3D 0; } - goto out; + goto out_close; =20 -err_out: - serrno =3D errno; - remove(buffer1); - errno =3D serrno; +err: + ret =3D -1; +err_undo_link: + unlinkat_preserve_errno(ndirfd, name, 0); +out_close: + close_preserve_errno(ndirfd); + close_preserve_errno(odirfd); out: - g_free(buffer1); - v9fs_string_free(&newpath); + g_free(oname); + g_free(odirpath); return ret; } =20