From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46953) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ciUHo-0000bd-84 for qemu-devel@nongnu.org; Mon, 27 Feb 2017 18:00:59 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ciUHl-00040b-CQ for qemu-devel@nongnu.org; Mon, 27 Feb 2017 18:00:56 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:34058 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 1ciUHl-0003zx-6b for qemu-devel@nongnu.org; Mon, 27 Feb 2017 18:00:53 -0500 Received: from pps.filterd (m0098417.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v1RMrc5D080992 for ; Mon, 27 Feb 2017 18:00:52 -0500 Received: from e06smtp10.uk.ibm.com (e06smtp10.uk.ibm.com [195.75.94.106]) by mx0a-001b2d01.pphosted.com with ESMTP id 28vm1wankr-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 27 Feb 2017 18:00:52 -0500 Received: from localhost by e06smtp10.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 27 Feb 2017 23:00:50 -0000 From: Greg Kurz Date: Tue, 28 Feb 2017 00:00:08 +0100 In-Reply-To: <1488236421-30983-1-git-send-email-groug@kaod.org> References: <1488236421-30983-1-git-send-email-groug@kaod.org> Message-Id: <1488236421-30983-19-git-send-email-groug@kaod.org> Subject: [Qemu-devel] [PULL 18/31] 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: Peter Maydell , "Aneesh Kumar K.V" , Greg Kurz 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 Reviewed-by: Stefan Hajnoczi --- 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 ae5d26821791..c6c114839287 100644 --- a/hw/9pfs/9p-local.c +++ b/hw/9pfs/9p-local.c @@ -894,13 +894,14 @@ 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; } -- 2.7.4