From nobody Thu Nov 6 19:45:39 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 1488149597859231.99061920963652; Sun, 26 Feb 2017 14:53:17 -0800 (PST) Received: from localhost ([::1]:48790 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ci7gq-0005P0-Cz for importer@patchew.org; Sun, 26 Feb 2017 17:53:16 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50530) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ci7Wg-00051H-0N for qemu-devel@nongnu.org; Sun, 26 Feb 2017 17:42:49 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ci7Wc-0002ph-SB for qemu-devel@nongnu.org; Sun, 26 Feb 2017 17:42:46 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:42974) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ci7Wc-0002pS-I0 for qemu-devel@nongnu.org; Sun, 26 Feb 2017 17:42:42 -0500 Received: from pps.filterd (m0098396.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v1QMcesr070066 for ; Sun, 26 Feb 2017 17:42:41 -0500 Received: from e31.co.us.ibm.com (e31.co.us.ibm.com [32.97.110.149]) by mx0a-001b2d01.pphosted.com with ESMTP id 28u6xmv0gq-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Sun, 26 Feb 2017 17:42:41 -0500 Received: from localhost by e31.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Sun, 26 Feb 2017 15:42:38 -0700 Received: from b03cxnp08025.gho.boulder.ibm.com (b03cxnp08025.gho.boulder.ibm.com [9.17.130.17]) by d03dlp01.boulder.ibm.com (Postfix) with ESMTP id 4F66E1FF001E; Sun, 26 Feb 2017 15:42:15 -0700 (MST) Received: from b03ledav002.gho.boulder.ibm.com (b03ledav002.gho.boulder.ibm.com [9.17.130.233]) by b03cxnp08025.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v1QMgckt10223932; Sun, 26 Feb 2017 15:42:38 -0700 Received: from b03ledav002.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id F08C3136048; Sun, 26 Feb 2017 15:42:37 -0700 (MST) Received: from [192.168.66.23] (unknown [9.164.183.34]) by b03ledav002.gho.boulder.ibm.com (Postfix) with ESMTP id 37D9A13603C; Sun, 26 Feb 2017 15:42:36 -0700 (MST) From: Greg Kurz To: qemu-devel@nongnu.org Date: Sun, 26 Feb 2017 23:42:34 +0100 In-Reply-To: <148814889214.28146.16915712763478774662.stgit@bahia> References: <148814889214.28146.16915712763478774662.stgit@bahia> 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: 17022622-8235-0000-0000-00000B0E415E X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00006689; HX=3.00000240; KW=3.00000007; PH=3.00000004; SC=3.00000204; SDB=6.00827424; UDB=6.00405424; IPR=6.00604940; BA=6.00005172; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00014449; XFM=3.00000011; UTC=2017-02-26 22:42:40 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17022622-8236-0000-0000-000039EBE2FC Message-Id: <148814895464.28146.14337427309543597613.stgit@bahia> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2017-02-26_11:, , 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-1702260233 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 v2 08/28] 9pfs: local: llistxattr: 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_llistxattr() callback is vulnerable to symlink attacks because it calls llistxattr() which follows symbolic links in all path elements but the rightmost one. This patch introduces a helper to emulate the non-existing flistxattrat() function: it is implemented with /proc/self/fd which provides a trusted path that can be safely passed to llistxattr(). local_llistxattr() is converted to use this helper and opendir_nofollow(). This partly fixes CVE-2016-9602. Signed-off-by: Greg Kurz Reviewed-by: Stefan Hajnoczi --- v2: - introduce /proc based flistxattrat_nofollow() --- hw/9pfs/9p-xattr.c | 35 +++++++++++++++++++++++++++++------ 1 file changed, 29 insertions(+), 6 deletions(-) diff --git a/hw/9pfs/9p-xattr.c b/hw/9pfs/9p-xattr.c index aa4391e6b317..54193c630c9d 100644 --- a/hw/9pfs/9p-xattr.c +++ b/hw/9pfs/9p-xattr.c @@ -60,6 +60,16 @@ ssize_t pt_listxattr(FsContext *ctx, const char *path, return name_size; } =20 +static ssize_t flistxattrat_nofollow(int dirfd, const char *filename, + char *list, size_t size) +{ + char *proc_path =3D g_strdup_printf("/proc/self/fd/%d/%s", dirfd, file= name); + int ret; + + ret =3D llistxattr(proc_path, list, size); + g_free(proc_path); + return ret; +} =20 /* * Get the list and pass to each layer to find out whether @@ -69,24 +79,37 @@ ssize_t v9fs_list_xattr(FsContext *ctx, const char *pat= h, void *value, size_t vsize) { ssize_t size =3D 0; - char *buffer; void *ovalue =3D value; XattrOperations *xops; char *orig_value, *orig_value_start; ssize_t xattr_len, parsed_len =3D 0, attr_len; + char *dirpath, *name; + int dirfd; =20 /* Get the actual len */ - buffer =3D rpath(ctx, path); - xattr_len =3D llistxattr(buffer, value, 0); + dirpath =3D g_path_get_dirname(path); + dirfd =3D local_opendir_nofollow(ctx, dirpath); + g_free(dirpath); + if (dirfd =3D=3D -1) { + return -1; + } + + name =3D g_path_get_basename(path); + xattr_len =3D flistxattrat_nofollow(dirfd, name, value, 0); if (xattr_len <=3D 0) { - g_free(buffer); + g_free(name); + close_preserve_errno(dirfd); return xattr_len; } =20 /* Now fetch the xattr and find the actual size */ orig_value =3D g_malloc(xattr_len); - xattr_len =3D llistxattr(buffer, orig_value, xattr_len); - g_free(buffer); + xattr_len =3D flistxattrat_nofollow(dirfd, name, orig_value, xattr_len= ); + g_free(name); + close_preserve_errno(dirfd); + if (xattr_len < 0) { + return -1; + } =20 /* store the orig pointer */ orig_value_start =3D orig_value;