From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46899) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ciUHl-0000Ye-PD for qemu-devel@nongnu.org; Mon, 27 Feb 2017 18:00:57 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ciUHk-0003zr-Po for qemu-devel@nongnu.org; Mon, 27 Feb 2017 18:00:53 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:47244 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 1ciUHk-0003yr-IV for qemu-devel@nongnu.org; Mon, 27 Feb 2017 18:00:52 -0500 Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v1RMrbx0010739 for ; Mon, 27 Feb 2017 18:00:51 -0500 Received: from e06smtp06.uk.ibm.com (e06smtp06.uk.ibm.com [195.75.94.102]) by mx0b-001b2d01.pphosted.com with ESMTP id 28vp2342ev-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 27 Feb 2017 18:00:51 -0500 Received: from localhost by e06smtp06.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 00:00:06 +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: <1488236421-30983-17-git-send-email-groug@kaod.org> Subject: [Qemu-devel] [PULL 16/31] 9pfs: local: utimensat: 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_utimensat() callback is vulnerable to symlink attacks because it calls qemu_utimens()->utimensat(AT_SYMLINK_NOFOLLOW) which follows symbolic links in all path elements but the rightmost one or qemu_utimens()->utimes() which follows symbolic links for all path elements. This patch converts local_utimensat() to rely on opendir_nofollow() and utimensat(AT_SYMLINK_NOFOLLOW) directly instead of using qemu_utimens(). It is hence assumed that the OS supports utimensat(), i.e. has glibc 2.6 or higher and linux 2.6.22 or higher, which seems reasonable nowadays. This partly fixes CVE-2016-9602. Signed-off-by: Greg Kurz Reviewed-by: Stefan Hajnoczi --- hw/9pfs/9p-local.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c index 53a2fd50edbb..bab095353da7 100644 --- a/hw/9pfs/9p-local.c +++ b/hw/9pfs/9p-local.c @@ -959,13 +959,20 @@ static int local_chown(FsContext *fs_ctx, V9fsPath *fs_path, FsCred *credp) static int local_utimensat(FsContext *s, V9fsPath *fs_path, const struct timespec *buf) { - char *buffer; - int ret; - char *path = fs_path->data; + char *dirpath = g_path_get_dirname(fs_path->data); + char *name = g_path_get_basename(fs_path->data); + int dirfd, ret = -1; - buffer = rpath(s, path); - ret = qemu_utimens(buffer, buf); - g_free(buffer); + dirfd = local_opendir_nofollow(s, dirpath); + if (dirfd == -1) { + goto out; + } + + ret = utimensat(dirfd, name, buf, AT_SYMLINK_NOFOLLOW); + close_preserve_errno(dirfd); +out: + g_free(dirpath); + g_free(name); return ret; } -- 2.7.4