From nobody Thu Nov 6 19:57:09 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 1488150233538323.4973281085719; Sun, 26 Feb 2017 15:03:53 -0800 (PST) Received: from localhost ([::1]:48849 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ci7r5-0006Px-Nx for importer@patchew.org; Sun, 26 Feb 2017 18:03:51 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50658) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ci7XE-0005dD-Ee for qemu-devel@nongnu.org; Sun, 26 Feb 2017 17:43:23 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ci7XB-0002vc-A3 for qemu-devel@nongnu.org; Sun, 26 Feb 2017 17:43:20 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:50844 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 1ci7XB-0002vU-3W for qemu-devel@nongnu.org; Sun, 26 Feb 2017 17:43:17 -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 v1QMcd9K087160 for ; Sun, 26 Feb 2017 17:43:16 -0500 Received: from e34.co.us.ibm.com (e34.co.us.ibm.com [32.97.110.152]) by mx0a-001b2d01.pphosted.com with ESMTP id 28u862td80-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Sun, 26 Feb 2017 17:43:16 -0500 Received: from localhost by e34.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Sun, 26 Feb 2017 15:43:12 -0700 Received: from b03cxnp08028.gho.boulder.ibm.com (b03cxnp08028.gho.boulder.ibm.com [9.17.130.20]) by d03dlp01.boulder.ibm.com (Postfix) with ESMTP id 7EE271FF0021; Sun, 26 Feb 2017 15:42:49 -0700 (MST) Received: from b03ledav006.gho.boulder.ibm.com (b03ledav006.gho.boulder.ibm.com [9.17.130.237]) by b03cxnp08028.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v1QMhCxh2490798; Sun, 26 Feb 2017 15:43:12 -0700 Received: from b03ledav006.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2B01FC6042; Sun, 26 Feb 2017 15:43:12 -0700 (MST) Received: from [192.168.66.23] (unknown [9.164.183.34]) by b03ledav006.gho.boulder.ibm.com (Postfix) with ESMTP id 563ACC603C; Sun, 26 Feb 2017 15:43:10 -0700 (MST) From: Greg Kurz To: qemu-devel@nongnu.org Date: Sun, 26 Feb 2017 23:43:08 +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: 17022622-0016-0000-0000-000006484FAA 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 22:43:14 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17022622-0017-0000-0000-000037BD3B3E Message-Id: <148814898890.28146.12107417177877261380.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: 148.163.158.5 Subject: [Qemu-devel] [PATCH v2 12/28] 9pfs: local: remove: 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_remove() callback is vulnerable to symlink attacks because it calls: (1) lstat() which follows symbolic links in all path elements but the rightmost one (2) remove() which follows symbolic links in all path elements but the rightmost one This patch converts local_remove() to rely on opendir_nofollow(), fstatat(AT_SYMLINK_NOFOLLOW) to fix (1) and unlinkat() to fix (2). This partly fixes CVE-2016-9602. Signed-off-by: Greg Kurz Reviewed-by: Stefan Hajnoczi --- hw/9pfs/9p-local.c | 64 +++++++++++++++++-------------------------------= ---- 1 file changed, 21 insertions(+), 43 deletions(-) diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c index 69439714cd91..b118a7632362 100644 --- a/hw/9pfs/9p-local.c +++ b/hw/9pfs/9p-local.c @@ -1021,54 +1021,32 @@ err_out: =20 static int local_remove(FsContext *ctx, const char *path) { - int err; struct stat stbuf; - char *buffer; + char *dirpath =3D g_path_get_dirname(path); + char *name =3D g_path_get_basename(path); + int flags =3D 0; + int dirfd; + int err =3D -1; =20 - if (ctx->export_flags & V9FS_SM_MAPPED_FILE) { - buffer =3D rpath(ctx, path); - err =3D lstat(buffer, &stbuf); - g_free(buffer); - if (err) { - goto err_out; - } - /* - * If directory remove .virtfs_metadata contained in the - * directory - */ - if (S_ISDIR(stbuf.st_mode)) { - buffer =3D g_strdup_printf("%s/%s/%s", ctx->fs_root, - path, VIRTFS_META_DIR); - err =3D remove(buffer); - g_free(buffer); - if (err < 0 && errno !=3D ENOENT) { - /* - * We didn't had the .virtfs_metadata file. May be file cr= eated - * in non-mapped mode ?. Ignore ENOENT. - */ - goto err_out; - } - } - /* - * Now remove the name from parent directory - * .virtfs_metadata directory - */ - buffer =3D local_mapped_attr_path(ctx, path); - err =3D remove(buffer); - g_free(buffer); - if (err < 0 && errno !=3D ENOENT) { - /* - * We didn't had the .virtfs_metadata file. May be file created - * in non-mapped mode ?. Ignore ENOENT. - */ - goto err_out; - } + dirfd =3D local_opendir_nofollow(ctx, dirpath); + if (dirfd) { + goto out; } =20 - buffer =3D rpath(ctx, path); - err =3D remove(buffer); - g_free(buffer); + if (fstatat(dirfd, path, &stbuf, AT_SYMLINK_NOFOLLOW) < 0) { + goto err_out; + } + + if (S_ISDIR(stbuf.st_mode)) { + flags |=3D AT_REMOVEDIR; + } + + err =3D local_unlinkat_common(ctx, dirfd, name, flags); err_out: + close_preserve_errno(dirfd); +out: + g_free(name); + g_free(dirpath); return err; } =20