From patchwork Mon Mar 20 23:07:42 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Michael Roth X-Patchwork-Id: 741248 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3vnBcC1Rrjz9rvt for ; Tue, 21 Mar 2017 10:14:51 +1100 (AEDT) Received: from localhost ([::1]:35488 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cq6Vk-0005dB-G9 for incoming@patchwork.ozlabs.org; Mon, 20 Mar 2017 19:14:48 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40410) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cq6QW-0001Rb-PU for qemu-devel@nongnu.org; Mon, 20 Mar 2017 19:09:28 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cq6QT-0004in-41 for qemu-devel@nongnu.org; Mon, 20 Mar 2017 19:09:24 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:44925 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 1cq6QS-0004iO-U0 for qemu-devel@nongnu.org; Mon, 20 Mar 2017 19:09:21 -0400 Received: from pps.filterd (m0098419.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v2KN8ptT008189 for ; Mon, 20 Mar 2017 19:09:20 -0400 Received: from e15.ny.us.ibm.com (e15.ny.us.ibm.com [129.33.205.205]) by mx0b-001b2d01.pphosted.com with ESMTP id 29afu7a7vy-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 20 Mar 2017 19:09:20 -0400 Received: from localhost by e15.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Mon, 20 Mar 2017 19:09:17 -0400 Received: from b01ledav03.gho.pok.ibm.com (b01ledav003.gho.pok.ibm.com [9.57.199.108]) by b01cxnp22033.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v2KN9HQ343647160; Mon, 20 Mar 2017 23:09:17 GMT Received: from b01ledav03.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 6C35BB2046; Mon, 20 Mar 2017 19:09:13 -0400 (EDT) Received: from localhost (unknown [9.53.92.194]) by b01ledav03.gho.pok.ibm.com (Postfix) with ESMTP id 51309B2054; Mon, 20 Mar 2017 19:09:13 -0400 (EDT) From: Michael Roth To: qemu-devel@nongnu.org Date: Mon, 20 Mar 2017 18:07:42 -0500 X-Mailer: git-send-email 2.7.4 In-Reply-To: <1490051325-3770-1-git-send-email-mdroth@linux.vnet.ibm.com> References: <1490051325-3770-1-git-send-email-mdroth@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 17032023-0036-0000-0000-000001B88DA7 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00006819; HX=3.00000240; KW=3.00000007; PH=3.00000004; SC=3.00000206; SDB=6.00836553; UDB=6.00411161; IPR=6.00614321; BA=6.00005224; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00014732; XFM=3.00000013; UTC=2017-03-20 23:09:18 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17032023-0037-0000-0000-00003F0DBB52 Message-Id: <1490051325-3770-19-git-send-email-mdroth@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2017-03-20_16:, , 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=8.0.1-1702020001 definitions=main-1703200196 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 18/81] 9pfs: local: renameat: 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: Greg Kurz , qemu-stable@nongnu.org, Greg Kurz Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" From: Greg Kurz The local_renameat() callback is currently a wrapper around local_rename() which is vulnerable to symlink attacks. This patch rewrites local_renameat() to have its own implementation, based on local_opendir_nofollow() and renameat(). This partly fixes CVE-2016-9602. Signed-off-by: Greg Kurz Reviewed-by: Stefan Hajnoczi (cherry picked from commit 99f2cf4b2dad7b37c69759deb0d0b19d3ec1a24a) Signed-off-by: Greg Kurz Signed-off-by: Michael Roth --- hw/9pfs/9p-local.c | 74 ++++++++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 64 insertions(+), 10 deletions(-) diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c index 547baa4..f2adf25 100644 --- a/hw/9pfs/9p-local.c +++ b/hw/9pfs/9p-local.c @@ -67,6 +67,14 @@ int local_opendir_nofollow(FsContext *fs_ctx, const char *path) return local_open_nofollow(fs_ctx, path, O_DIRECTORY | O_RDONLY, 0); } +static void renameat_preserve_errno(int odirfd, const char *opath, int ndirfd, + const char *npath) +{ + int serrno = errno; + renameat(odirfd, opath, ndirfd, npath); + errno = serrno; +} + #define VIRTFS_META_DIR ".virtfs_metadata" static char *local_mapped_attr_path(FsContext *ctx, const char *path) @@ -146,8 +154,7 @@ static void local_mapped_file_attr(int dirfd, const char *name, char buf[ATTR_MAX]; int map_dirfd; - map_dirfd = openat(dirfd, VIRTFS_META_DIR, - O_RDONLY | O_DIRECTORY | O_NOFOLLOW); + map_dirfd = openat_dir(dirfd, VIRTFS_META_DIR); if (map_dirfd == -1) { return; } @@ -1187,17 +1194,64 @@ static int local_renameat(FsContext *ctx, V9fsPath *olddir, const char *new_name) { int ret; - V9fsString old_full_name, new_full_name; + int odirfd, ndirfd; + + odirfd = local_opendir_nofollow(ctx, olddir->data); + if (odirfd == -1) { + return -1; + } + + ndirfd = local_opendir_nofollow(ctx, newdir->data); + if (ndirfd == -1) { + close_preserve_errno(odirfd); + return -1; + } + + ret = renameat(odirfd, old_name, ndirfd, new_name); + if (ret < 0) { + goto out; + } - v9fs_string_init(&old_full_name); - v9fs_string_init(&new_full_name); + if (ctx->export_flags & V9FS_SM_MAPPED_FILE) { + int omap_dirfd, nmap_dirfd; - v9fs_string_sprintf(&old_full_name, "%s/%s", olddir->data, old_name); - v9fs_string_sprintf(&new_full_name, "%s/%s", newdir->data, new_name); + ret = mkdirat(ndirfd, VIRTFS_META_DIR, 0700); + if (ret < 0 && errno != EEXIST) { + goto err_undo_rename; + } - ret = local_rename(ctx, old_full_name.data, new_full_name.data); - v9fs_string_free(&old_full_name); - v9fs_string_free(&new_full_name); + omap_dirfd = openat(odirfd, VIRTFS_META_DIR, + O_RDONLY | O_DIRECTORY | O_NOFOLLOW); + if (omap_dirfd == -1) { + goto err; + } + + nmap_dirfd = openat(ndirfd, VIRTFS_META_DIR, + O_RDONLY | O_DIRECTORY | O_NOFOLLOW); + if (nmap_dirfd == -1) { + close_preserve_errno(omap_dirfd); + goto err; + } + + /* rename the .virtfs_metadata files */ + ret = renameat(omap_dirfd, old_name, nmap_dirfd, new_name); + close_preserve_errno(nmap_dirfd); + close_preserve_errno(omap_dirfd); + if (ret < 0 && errno != ENOENT) { + goto err_undo_rename; + } + + ret = 0; + } + goto out; + +err: + ret = -1; +err_undo_rename: + renameat_preserve_errno(ndirfd, new_name, odirfd, old_name); +out: + close_preserve_errno(ndirfd); + close_preserve_errno(odirfd); return ret; }