From patchwork Mon Mar 20 23:07:36 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Michael Roth X-Patchwork-Id: 741253 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 3vnBhN5gcWz9ryr for ; Tue, 21 Mar 2017 10:18:28 +1100 (AEDT) Received: from localhost ([::1]:35509 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cq6ZG-0000B8-41 for incoming@patchwork.ozlabs.org; Mon, 20 Mar 2017 19:18:26 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40365) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cq6QW-0001Qy-DH for qemu-devel@nongnu.org; Mon, 20 Mar 2017 19:09:26 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cq6QS-0004i4-Dt for qemu-devel@nongnu.org; Mon, 20 Mar 2017 19:09:23 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:46812 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-0004ga-6x for qemu-devel@nongnu.org; Mon, 20 Mar 2017 19:09:20 -0400 Received: from pps.filterd (m0098414.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v2KN8W5e084386 for ; Mon, 20 Mar 2017 19:09:19 -0400 Received: from e11.ny.us.ibm.com (e11.ny.us.ibm.com [129.33.205.201]) by mx0b-001b2d01.pphosted.com with ESMTP id 29amb2aayg-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 20 Mar 2017 19:09:19 -0400 Received: from localhost by e11.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Mon, 20 Mar 2017 19:09:15 -0400 Received: from b01ledav002.gho.pok.ibm.com (b01ledav002.gho.pok.ibm.com [9.57.199.107]) by b01cxnp22033.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v2KN9E4r43647130; Mon, 20 Mar 2017 23:09:14 GMT Received: from b01ledav002.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A7B82124049; Mon, 20 Mar 2017 19:09:10 -0400 (EDT) Received: from localhost (unknown [9.53.92.194]) by b01ledav002.gho.pok.ibm.com (Postfix) with ESMTP id 8C6A1124035; Mon, 20 Mar 2017 19:09:10 -0400 (EDT) From: Michael Roth To: qemu-devel@nongnu.org Date: Mon, 20 Mar 2017 18:07:36 -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: 17032023-2213-0000-0000-0000016A7CA4 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00006819; HX=3.00000240; KW=3.00000007; PH=3.00000004; SC=3.00000206; SDB=6.00836552; UDB=6.00411161; IPR=6.00614322; 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 23:09:16 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17032023-2214-0000-0000-000054D5903D Message-Id: <1490051325-3770-13-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 12/81] 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: 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_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 (cherry picked from commit a0e640a87210b1e986bcd4e7f7de03beb3db0a4a) Signed-off-by: Greg Kurz Signed-off-by: Michael Roth --- 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 a72adb8..9caee0e 100644 --- a/hw/9pfs/9p-local.c +++ b/hw/9pfs/9p-local.c @@ -1022,54 +1022,32 @@ err_out: static int local_remove(FsContext *ctx, const char *path) { - int err; struct stat stbuf; - char *buffer; + char *dirpath = g_path_get_dirname(path); + char *name = g_path_get_basename(path); + int flags = 0; + int dirfd; + int err = -1; - if (ctx->export_flags & V9FS_SM_MAPPED_FILE) { - buffer = rpath(ctx, path); - err = 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 = g_strdup_printf("%s/%s/%s", ctx->fs_root, - path, VIRTFS_META_DIR); - err = remove(buffer); - g_free(buffer); - if (err < 0 && errno != ENOENT) { - /* - * We didn't had the .virtfs_metadata file. May be file created - * in non-mapped mode ?. Ignore ENOENT. - */ - goto err_out; - } - } - /* - * Now remove the name from parent directory - * .virtfs_metadata directory - */ - buffer = local_mapped_attr_path(ctx, path); - err = remove(buffer); - g_free(buffer); - if (err < 0 && errno != ENOENT) { - /* - * We didn't had the .virtfs_metadata file. May be file created - * in non-mapped mode ?. Ignore ENOENT. - */ - goto err_out; - } + dirfd = local_opendir_nofollow(ctx, dirpath); + if (dirfd) { + goto out; } - buffer = rpath(ctx, path); - err = remove(buffer); - g_free(buffer); + if (fstatat(dirfd, path, &stbuf, AT_SYMLINK_NOFOLLOW) < 0) { + goto err_out; + } + + if (S_ISDIR(stbuf.st_mode)) { + flags |= AT_REMOVEDIR; + } + + err = local_unlinkat_common(ctx, dirfd, name, flags); err_out: + close_preserve_errno(dirfd); +out: + g_free(name); + g_free(dirpath); return err; }