Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933367AbcKNQzX (ORCPT ); Mon, 14 Nov 2016 11:55:23 -0500 Received: from mail-pf0-f171.google.com ([209.85.192.171]:35744 "EHLO mail-pf0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753258AbcKNQzV (ORCPT ); Mon, 14 Nov 2016 11:55:21 -0500 Subject: Re: [PATCH v3] ip6_output: ensure flow saddr actually belongs to device To: Hannes Frederic Sowa , "Jason A. Donenfeld" , Netdev , WireGuard mailing list , LKML , YOSHIFUJI Hideaki References: <27cccef1-06d9-74b3-5b8a-912850119a76@cumulusnetworks.com> <20161113232813.28926-1-Jason@zx2c4.com> <1479141867.3723362.787321689.4A3DCFD6@webmail.messagingengine.com> From: David Ahern Message-ID: Date: Mon, 14 Nov 2016 09:55:18 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <1479141867.3723362.787321689.4A3DCFD6@webmail.messagingengine.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2044 Lines: 46 On 11/14/16 9:44 AM, Hannes Frederic Sowa wrote: > On Mon, Nov 14, 2016, at 00:28, Jason A. Donenfeld wrote: >> This puts the IPv6 routing functions in parity with the IPv4 routing >> functions. Namely, we now check in v6 that if a flowi6 requests an >> saddr, the returned dst actually corresponds to a net device that has >> that saddr. This mirrors the v4 logic with __ip_dev_find in >> __ip_route_output_key_hash. In the event that the returned dst is not >> for a dst with a dev that has the saddr, we return -EINVAL, just like >> v4; this makes it easy to use the same error handlers for both cases. >> >> Signed-off-by: Jason A. Donenfeld >> Cc: David Ahern >> --- >> Changes from v2: >> It turns out ipv6_chk_addr already has the device enumeration >> logic that we need by simply passing NULL. >> >> net/ipv6/ip6_output.c | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c >> index 6001e78..b3b5cb6 100644 >> --- a/net/ipv6/ip6_output.c >> +++ b/net/ipv6/ip6_output.c >> @@ -926,6 +926,10 @@ static int ip6_dst_lookup_tail(struct net *net, >> const struct sock *sk, >> int err; >> int flags = 0; >> >> + if (!ipv6_addr_any(&fl6->saddr) && >> + !ipv6_chk_addr(net, &fl6->saddr, NULL, 1)) >> + return -EINVAL; > > Hmm, this check is too permissive, no? > > E.g. what happens if you move a link local address from one interface to > another? In this case this code would still allow the saddr to be used. This check -- like the ipv4 variant -- only verifies the saddr is locally assigned. If the address moves interfaces it should be fine. > > I just also quickly read up on the history (sorry was travelling last > week) and wonder if you ever saw a user space facing bug or if this is > basically some difference you saw while writing out of tree code? I checked the userspace API this morning. bind and cmsg for example check that the address is valid with calls to ipv6_chk_addr.