Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S969325AbdD1Ixw (ORCPT ); Fri, 28 Apr 2017 04:53:52 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:55478 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1164951AbdD1Iay (ORCPT ); Fri, 28 Apr 2017 04:30:54 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Phil Turnbull , Pablo Neira Ayuso , Ben Hutchings Subject: [PATCH 4.4 12/17] netfilter: nfnetlink: correctly validate length of batch messages Date: Fri, 28 Apr 2017 10:30:25 +0200 Message-Id: <20170428082912.076133196@linuxfoundation.org> X-Mailer: git-send-email 2.12.2 In-Reply-To: <20170428082910.160564394@linuxfoundation.org> References: <20170428082910.160564394@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3539 Lines: 78 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Phil Turnbull commit c58d6c93680f28ac58984af61d0a7ebf4319c241 upstream. If nlh->nlmsg_len is zero then an infinite loop is triggered because 'skb_pull(skb, msglen);' pulls zero bytes. The calculation in nlmsg_len() underflows if 'nlh->nlmsg_len < NLMSG_HDRLEN' which bypasses the length validation and will later trigger an out-of-bound read. If the length validation does fail then the malformed batch message is copied back to userspace. However, we cannot do this because the nlh->nlmsg_len can be invalid. This leads to an out-of-bounds read in netlink_ack: [ 41.455421] ================================================================== [ 41.456431] BUG: KASAN: slab-out-of-bounds in memcpy+0x1d/0x40 at addr ffff880119e79340 [ 41.456431] Read of size 4294967280 by task a.out/987 [ 41.456431] ============================================================================= [ 41.456431] BUG kmalloc-512 (Not tainted): kasan: bad access detected [ 41.456431] ----------------------------------------------------------------------------- ... [ 41.456431] Bytes b4 ffff880119e79310: 00 00 00 00 d5 03 00 00 b0 fb fe ff 00 00 00 00 ................ [ 41.456431] Object ffff880119e79320: 20 00 00 00 10 00 05 00 00 00 00 00 00 00 00 00 ............... [ 41.456431] Object ffff880119e79330: 14 00 0a 00 01 03 fc 40 45 56 11 22 33 10 00 05 .......@EV."3... [ 41.456431] Object ffff880119e79340: f0 ff ff ff 88 99 aa bb 00 14 00 0a 00 06 fe fb ................ ^^ start of batch nlmsg with nlmsg_len=4294967280 ... [ 41.456431] Memory state around the buggy address: [ 41.456431] ffff880119e79400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ 41.456431] ffff880119e79480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ 41.456431] >ffff880119e79500: 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc [ 41.456431] ^ [ 41.456431] ffff880119e79580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 41.456431] ffff880119e79600: fc fc fc fc fc fc fc fc fc fc fb fb fb fb fb fb [ 41.456431] ================================================================== Fix this with better validation of nlh->nlmsg_len and by setting NFNL_BATCH_FAILURE if any batch message fails length validation. CAP_NET_ADMIN is required to trigger the bugs. Fixes: 9ea2aa8b7dba ("netfilter: nfnetlink: validate nfnetlink header from batch") Signed-off-by: Phil Turnbull Signed-off-by: Pablo Neira Ayuso Cc: Ben Hutchings Signed-off-by: Greg Kroah-Hartman --- net/netfilter/nfnetlink.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) --- a/net/netfilter/nfnetlink.c +++ b/net/netfilter/nfnetlink.c @@ -326,10 +326,12 @@ replay: nlh = nlmsg_hdr(skb); err = 0; - if (nlmsg_len(nlh) < sizeof(struct nfgenmsg) || - skb->len < nlh->nlmsg_len) { - err = -EINVAL; - goto ack; + if (nlh->nlmsg_len < NLMSG_HDRLEN || + skb->len < nlh->nlmsg_len || + nlmsg_len(nlh) < sizeof(struct nfgenmsg)) { + nfnl_err_reset(&err_list); + status |= NFNL_BATCH_FAILURE; + goto done; } /* Only requests are handled by the kernel */