From nobody Mon Feb 9 23:40:20 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 1488279254778892.5236638939922; Tue, 28 Feb 2017 02:54:14 -0800 (PST) Received: from localhost ([::1]:60124 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cifQ5-0003Nj-Dd for importer@patchew.org; Tue, 28 Feb 2017 05:54:13 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37614) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cif3h-0001EH-Ck for qemu-devel@nongnu.org; Tue, 28 Feb 2017 05:31:09 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cif3e-0007xn-7r for qemu-devel@nongnu.org; Tue, 28 Feb 2017 05:31:05 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:35123 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 1cif3d-0007xL-Uo for qemu-devel@nongnu.org; Tue, 28 Feb 2017 05:31:02 -0500 Received: from pps.filterd (m0098413.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v1SATFsr093671 for ; Tue, 28 Feb 2017 05:31:01 -0500 Received: from e06smtp07.uk.ibm.com (e06smtp07.uk.ibm.com [195.75.94.103]) by mx0b-001b2d01.pphosted.com with ESMTP id 28w28kny7a-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Tue, 28 Feb 2017 05:31:01 -0500 Received: from localhost by e06smtp07.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Tue, 28 Feb 2017 10:30:57 -0000 Received: from b06cxnps3074.portsmouth.uk.ibm.com (d06relay09.portsmouth.uk.ibm.com [9.149.109.194]) by d06dlp01.portsmouth.uk.ibm.com (Postfix) with ESMTP id 3A0D817D8056; Tue, 28 Feb 2017 10:34:10 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v1SAUvxu15663552; Tue, 28 Feb 2017 10:30:57 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A967BAE051; Tue, 28 Feb 2017 09:28:46 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8D28BAE05A; Tue, 28 Feb 2017 09:28:46 +0000 (GMT) Received: from smtp.lab.toulouse-stg.fr.ibm.com (unknown [9.101.4.1]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 28 Feb 2017 09:28:46 +0000 (GMT) Received: from bahia.lan (icon-9-164-183-34.megacenter.de.ibm.com [9.164.183.34]) by smtp.lab.toulouse-stg.fr.ibm.com (Postfix) with ESMTP id 191C1220748; Tue, 28 Feb 2017 11:30:56 +0100 (CET) From: Greg Kurz To: qemu-devel@nongnu.org Date: Tue, 28 Feb 2017 11:30:23 +0100 X-Mailer: git-send-email 2.7.4 In-Reply-To: <1488277840-18608-1-git-send-email-groug@kaod.org> References: <1488277840-18608-1-git-send-email-groug@kaod.org> X-TM-AS-GCONF: 00 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 17022810-0028-0000-0000-000002B341B9 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17022810-0029-0000-0000-00002287633D Message-Id: <1488277840-18608-12-git-send-email-groug@kaod.org> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2017-02-28_07:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=13 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1612050000 definitions=main-1702280098 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] [fuzzy] X-Received-From: 148.163.158.5 Subject: [Qemu-devel] [PULL 11/28] 9pfs: local: unlinkat: 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: Peter Maydell , "Aneesh Kumar K.V" , Greg Kurz Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RSF_0 Z_629925259 SPT_0 Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" The local_unlinkat() callback is vulnerable to symlink attacks because it calls remove() which follows symbolic links in all path elements but the rightmost one. This patch converts local_unlinkat() to rely on opendir_nofollow() and unlinkat() instead. Most of the code is moved to a separate local_unlinkat_common() helper which will be reused in a subsequent patch to fix the same issue in local_remove(). This partly fixes CVE-2016-9602. Signed-off-by: Greg Kurz Reviewed-by: Stefan Hajnoczi Reviewed-by: Stefan Hajnoczi --- hw/9pfs/9p-local.c | 99 ++++++++++++++++++++++++++++++--------------------= ---- 1 file changed, 56 insertions(+), 43 deletions(-) diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c index 2c491af623f9..04de511765d8 100644 --- a/hw/9pfs/9p-local.c +++ b/hw/9pfs/9p-local.c @@ -969,6 +969,56 @@ static int local_utimensat(FsContext *s, V9fsPath *fs_= path, return ret; } =20 +static int local_unlinkat_common(FsContext *ctx, int dirfd, const char *na= me, + int flags) +{ + int ret =3D -1; + + if (ctx->export_flags & V9FS_SM_MAPPED_FILE) { + int map_dirfd; + + if (flags =3D=3D AT_REMOVEDIR) { + int fd; + + fd =3D openat(dirfd, name, O_RDONLY | O_DIRECTORY | O_PATH); + if (fd =3D=3D -1) { + goto err_out; + } + /* + * If directory remove .virtfs_metadata contained in the + * directory + */ + ret =3D unlinkat(fd, VIRTFS_META_DIR, AT_REMOVEDIR); + close_preserve_errno(fd); + if (ret < 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. + */ + map_dirfd =3D openat_dir(dirfd, VIRTFS_META_DIR); + ret =3D unlinkat(map_dirfd, name, 0); + close_preserve_errno(map_dirfd); + if (ret < 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; + } + } + + ret =3D unlinkat(dirfd, name, flags); +err_out: + return ret; +} + static int local_remove(FsContext *ctx, const char *path) { int err; @@ -1118,52 +1168,15 @@ static int local_unlinkat(FsContext *ctx, V9fsPath = *dir, const char *name, int flags) { int ret; - V9fsString fullname; - char *buffer; - - v9fs_string_init(&fullname); + int dirfd; =20 - v9fs_string_sprintf(&fullname, "%s/%s", dir->data, name); - if (ctx->export_flags & V9FS_SM_MAPPED_FILE) { - if (flags =3D=3D AT_REMOVEDIR) { - /* - * If directory remove .virtfs_metadata contained in the - * directory - */ - buffer =3D g_strdup_printf("%s/%s/%s", ctx->fs_root, - fullname.data, VIRTFS_META_DIR); - ret =3D remove(buffer); - g_free(buffer); - if (ret < 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, fullname.data); - ret =3D remove(buffer); - g_free(buffer); - if (ret < 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, dir->data); + if (dirfd =3D=3D -1) { + return -1; } - /* Remove the name finally */ - buffer =3D rpath(ctx, fullname.data); - ret =3D remove(buffer); - g_free(buffer); =20 -err_out: - v9fs_string_free(&fullname); + ret =3D local_unlinkat_common(ctx, dirfd, name, flags); + close_preserve_errno(dirfd); return ret; } =20 --=20 2.7.4