From patchwork Sun Feb 26 22:43:40 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kurz X-Patchwork-Id: 732641 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 3vWgSk442Fz9s9r for ; Mon, 27 Feb 2017 10:06:30 +1100 (AEDT) Received: from localhost ([::1]:48863 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ci7tb-0008J9-3Y for incoming@patchwork.ozlabs.org; Sun, 26 Feb 2017 18:06:27 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50744) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ci7Xk-0006Gy-5f for qemu-devel@nongnu.org; Sun, 26 Feb 2017 17:43:55 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ci7Xh-0002zi-1g for qemu-devel@nongnu.org; Sun, 26 Feb 2017 17:43:52 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:59078 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 1ci7Xg-0002za-RH for qemu-devel@nongnu.org; Sun, 26 Feb 2017 17:43:48 -0500 Received: from pps.filterd (m0098421.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v1QMcPfk123743 for ; Sun, 26 Feb 2017 17:43:48 -0500 Received: from e17.ny.us.ibm.com (e17.ny.us.ibm.com [129.33.205.207]) by mx0a-001b2d01.pphosted.com with ESMTP id 28uqvksrkv-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Sun, 26 Feb 2017 17:43:48 -0500 Received: from localhost by e17.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Sun, 26 Feb 2017 17:43:43 -0500 Received: from b01cxnp22036.gho.pok.ibm.com (b01cxnp22036.gho.pok.ibm.com [9.57.198.26]) by d01dlp01.pok.ibm.com (Postfix) with ESMTP id 1207138C8054; Sun, 26 Feb 2017 17:43:44 -0500 (EST) Received: from b01ledav004.gho.pok.ibm.com (b01ledav004.gho.pok.ibm.com [9.57.199.109]) by b01cxnp22036.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v1QMhgvt53412056; Sun, 26 Feb 2017 22:43:42 GMT Received: from b01ledav004.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1E83C112034; Sun, 26 Feb 2017 17:43:42 -0500 (EST) Received: from [192.168.66.23] (unknown [9.164.183.34]) by b01ledav004.gho.pok.ibm.com (Postfix) with ESMTP id D0672112040; Sun, 26 Feb 2017 17:43:40 -0500 (EST) From: Greg Kurz To: qemu-devel@nongnu.org Date: Sun, 26 Feb 2017 23:43:40 +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 X-TM-AS-GCONF: 00 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 17022622-0040-0000-0000-000002B84CBB 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=6.00604939; 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 22:43:46 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17022622-0041-0000-0000-000006AB790A Message-Id: <148814902031.28146.9279629325183576435.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 16/28] 9pfs: local: readlink: 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+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" The local_readlink() callback is vulnerable to symlink attacks because it calls: (1) open(O_NOFOLLOW) which follows symbolic links for all path elements but the rightmost one (2) readlink() which follows symbolic links for all path elements but the rightmost one This patch converts local_readlink() to rely on open_nofollow() to fix (1) and opendir_nofollow(), readlinkat() to fix (2). This partly fixes CVE-2016-9602. Signed-off-by: Greg Kurz Reviewed-by: Stefan Hajnoczi --- hw/9pfs/9p-local.c | 26 +++++++++++++++++--------- 1 file changed, 17 insertions(+), 9 deletions(-) diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c index 1d460a35aa7f..a47b7476545a 100644 --- a/hw/9pfs/9p-local.c +++ b/hw/9pfs/9p-local.c @@ -340,27 +340,35 @@ static ssize_t local_readlink(FsContext *fs_ctx, V9fsPath *fs_path, char *buf, size_t bufsz) { ssize_t tsize = -1; - char *buffer; - char *path = fs_path->data; if ((fs_ctx->export_flags & V9FS_SM_MAPPED) || (fs_ctx->export_flags & V9FS_SM_MAPPED_FILE)) { int fd; - buffer = rpath(fs_ctx, path); - fd = open(buffer, O_RDONLY | O_NOFOLLOW); - g_free(buffer); + + fd = local_open_nofollow(fs_ctx, fs_path->data, O_RDONLY, 0); if (fd == -1) { return -1; } do { tsize = read(fd, (void *)buf, bufsz); } while (tsize == -1 && errno == EINTR); - close(fd); + close_preserve_errno(fd); } else if ((fs_ctx->export_flags & V9FS_SM_PASSTHROUGH) || (fs_ctx->export_flags & V9FS_SM_NONE)) { - buffer = rpath(fs_ctx, path); - tsize = readlink(buffer, buf, bufsz); - g_free(buffer); + char *dirpath = g_path_get_dirname(fs_path->data); + char *name = g_path_get_basename(fs_path->data); + int dirfd; + + dirfd = local_opendir_nofollow(fs_ctx, dirpath); + if (dirfd == -1) { + goto out; + } + + tsize = readlinkat(dirfd, name, buf, bufsz); + close_preserve_errno(dirfd); + out: + g_free(name); + g_free(dirpath); } return tsize; }