From nobody Tue Feb 10 06:07:31 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 1487603306089446.95556428811415; Mon, 20 Feb 2017 07:08:26 -0800 (PST) Received: from localhost ([::1]:39070 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cfpZf-0005l6-MO for importer@patchew.org; Mon, 20 Feb 2017 10:08:23 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54422) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cfp9t-0007QC-OR for qemu-devel@nongnu.org; Mon, 20 Feb 2017 09:41:49 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cfp9q-0003se-Iq for qemu-devel@nongnu.org; Mon, 20 Feb 2017 09:41:45 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:37869 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 1cfp9q-0003sY-Bu for qemu-devel@nongnu.org; Mon, 20 Feb 2017 09:41:42 -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 v1KEdP0T114362 for ; Mon, 20 Feb 2017 09:41:41 -0500 Received: from e38.co.us.ibm.com (e38.co.us.ibm.com [32.97.110.159]) by mx0b-001b2d01.pphosted.com with ESMTP id 28pgs4w9tp-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 20 Feb 2017 09:41:41 -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 07:41:36 -0700 Received: from b03cxnp08028.gho.boulder.ibm.com (b03cxnp08028.gho.boulder.ibm.com [9.17.130.20]) by d03dlp02.boulder.ibm.com (Postfix) with ESMTP id 1EEFF3E40047; Mon, 20 Feb 2017 07:41:36 -0700 (MST) Received: from b03ledav005.gho.boulder.ibm.com (b03ledav005.gho.boulder.ibm.com [9.17.130.236]) by b03cxnp08028.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v1KEfaZI15794634; Mon, 20 Feb 2017 07:41:36 -0700 Received: from b03ledav005.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id ED67CBE038; Mon, 20 Feb 2017 07:41:35 -0700 (MST) Received: from bahia.lan (unknown [9.164.137.25]) by b03ledav005.gho.boulder.ibm.com (Postfix) with ESMTP id 368C6BE04C; Mon, 20 Feb 2017 07:41:34 -0700 (MST) From: Greg Kurz To: qemu-devel@nongnu.org Date: Mon, 20 Feb 2017 15:41:32 +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: 17022014-0028-0000-0000-00000717A1DE 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 14:41:39 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17022014-0029-0000-0000-000033B879F0 Message-Id: <148760169288.31154.16807785388921473289.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 17/29] 9pfs: local: readlink: 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_readlink() callback is vulnerable to symlink attacks because it calls: (1) open(O_NOFOLLOW) which follows symbolic links for all path elements but the rightmost one (2) readlink() which follows symbolic links for all path elements but the rightmost one This patch converts local_readlink() to rely on open_nofollow() to fix (1) and opendir_nofollow(), readlinkat() to fix (2). 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 da233198d032..dbd5549283aa 100644 --- a/hw/9pfs/9p-local.c +++ b/hw/9pfs/9p-local.c @@ -334,27 +334,35 @@ static ssize_t local_readlink(FsContext *fs_ctx, V9fs= Path *fs_path, char *buf, size_t bufsz) { ssize_t tsize =3D -1; - char *buffer; - char *path =3D fs_path->data; =20 if ((fs_ctx->export_flags & V9FS_SM_MAPPED) || (fs_ctx->export_flags & V9FS_SM_MAPPED_FILE)) { int fd; - buffer =3D rpath(fs_ctx, path); - fd =3D open(buffer, O_RDONLY | O_NOFOLLOW); - g_free(buffer); + + fd =3D local_open_nofollow(fs_ctx, fs_path->data, O_RDONLY, 0); if (fd =3D=3D -1) { return -1; } do { tsize =3D read(fd, (void *)buf, bufsz); } while (tsize =3D=3D -1 && errno =3D=3D EINTR); - close(fd); + close_preserve_errno(fd); } else if ((fs_ctx->export_flags & V9FS_SM_PASSTHROUGH) || (fs_ctx->export_flags & V9FS_SM_NONE)) { - buffer =3D rpath(fs_ctx, path); - tsize =3D readlink(buffer, buf, bufsz); - g_free(buffer); + char *dirpath =3D g_path_get_dirname(fs_path->data); + char *name =3D g_path_get_basename(fs_path->data); + int dirfd; + + dirfd =3D local_opendir_nofollow(fs_ctx, dirpath); + if (dirfd =3D=3D -1) { + goto out; + } + + tsize =3D readlinkat(dirfd, name, buf, bufsz); + close_preserve_errno(dirfd); + out: + g_free(name); + g_free(dirpath); } return tsize; }