From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54363) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cfp9l-0007Fw-GC for qemu-devel@nongnu.org; Mon, 20 Feb 2017 09:41:40 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cfp9i-0003qv-BR for qemu-devel@nongnu.org; Mon, 20 Feb 2017 09:41:37 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:57004 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 1cfp9i-0003qY-59 for qemu-devel@nongnu.org; Mon, 20 Feb 2017 09:41:34 -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 v1KEdMQN134021 for ; Mon, 20 Feb 2017 09:41:33 -0500 Received: from e35.co.us.ibm.com (e35.co.us.ibm.com [32.97.110.153]) by mx0b-001b2d01.pphosted.com with ESMTP id 28qyr0y92a-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 20 Feb 2017 09:41:33 -0500 Received: from localhost by e35.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 20 Feb 2017 07:41:32 -0700 From: Greg Kurz Date: Mon, 20 Feb 2017 15:41:24 +0100 In-Reply-To: <148760155821.31154.13876757160410915057.stgit@bahia.lan> References: <148760155821.31154.13876757160410915057.stgit@bahia.lan> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <148760168489.31154.7921066936280376884.stgit@bahia.lan> Subject: [Qemu-devel] [PATCH 16/29] 9pfs: local: truncate: don't follow symlinks List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: "Daniel P. Berrange" , Jann Horn , Prasad J Pandit , Greg Kurz , "Aneesh Kumar K.V" , Stefan Hajnoczi The local_truncate() callback is vulnerable to symlink attacks because it calls truncate() which follows symbolic links in all path elements. This patch converts local_truncate() to rely on open_nofollow() and ftruncate() instead. This partly fixes CVE-2016-9602. Signed-off-by: Greg Kurz --- hw/9pfs/9p-local.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c index ebc12f3c0691..da233198d032 100644 --- a/hw/9pfs/9p-local.c +++ b/hw/9pfs/9p-local.c @@ -888,13 +888,14 @@ err_out: static int local_truncate(FsContext *ctx, V9fsPath *fs_path, off_t size) { - char *buffer; - int ret; - char *path = fs_path->data; + int fd, ret; - buffer = rpath(ctx, path); - ret = truncate(buffer, size); - g_free(buffer); + fd = local_open_nofollow(ctx, fs_path->data, O_WRONLY, 0); + if (fd == -1) { + return -1; + } + ret = ftruncate(fd, size); + close_preserve_errno(fd); return ret; }