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([2601:282:800:fd80:f191:fe61:9293:d1ca]) by smtp.googlemail.com with ESMTPSA id n21sm10537257ioh.30.2019.07.01.10.19.16 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 01 Jul 2019 10:19:16 -0700 (PDT) Subject: Re: [PATCH net v2] ipv4: don't set IPv6 only flags to IPv4 addresses To: Matteo Croce , netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org, "David S. Miller" , Alexey Kuznetsov , Hideaki YOSHIFUJI References: <20190701170155.1967-1-mcroce@redhat.com> From: David Ahern Message-ID: Date: Mon, 1 Jul 2019 11:19:15 -0600 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20190701170155.1967-1-mcroce@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/1/19 11:01 AM, Matteo Croce wrote: > Avoid the situation where an IPV6 only flag is applied to an IPv4 address: > > # ip addr add 192.0.2.1/24 dev dummy0 nodad home mngtmpaddr noprefixroute > # ip -4 addr show dev dummy0 > 2: dummy0: mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000 > inet 192.0.2.1/24 scope global noprefixroute dummy0 > valid_lft forever preferred_lft forever > > Or worse, by sending a malicious netlink command: > > # ip -4 addr show dev dummy0 > 2: dummy0: mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000 > inet 192.0.2.1/24 scope global nodad optimistic dadfailed home tentative mngtmpaddr noprefixroute stable-privacy dummy0 > valid_lft forever preferred_lft forever > > Signed-off-by: Matteo Croce > --- > net/ipv4/devinet.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c > index c6bd0f7a020a..c5ebfa199794 100644 > --- a/net/ipv4/devinet.c > +++ b/net/ipv4/devinet.c > @@ -62,6 +62,11 @@ > #include > #include > > +#define IPV6ONLY_FLAGS \ > + (IFA_F_NODAD | IFA_F_OPTIMISTIC | IFA_F_DADFAILED | \ > + IFA_F_HOMEADDRESS | IFA_F_TENTATIVE | \ > + IFA_F_MANAGETEMPADDR | IFA_F_STABLE_PRIVACY) > + > static struct ipv4_devconf ipv4_devconf = { > .data = { > [IPV4_DEVCONF_ACCEPT_REDIRECTS - 1] = 1, > @@ -468,6 +473,9 @@ static int __inet_insert_ifa(struct in_ifaddr *ifa, struct nlmsghdr *nlh, > ifa->ifa_flags &= ~IFA_F_SECONDARY; > last_primary = &in_dev->ifa_list; > > + /* Don't set IPv6 only flags to IPv4 addresses */ > + ifa->ifa_flags &= ~IPV6ONLY_FLAGS; > + > for (ifap = &in_dev->ifa_list; (ifa1 = *ifap) != NULL; > ifap = &ifa1->ifa_next) { > if (!(ifa1->ifa_flags & IFA_F_SECONDARY) && > I guess at this point we can fail the address add, so this is the best option. rtm_to_ifaddr could set a message in extack about invalid flags - not fail the change, just warn the user that flags will be ignored. Reviewed-by: David Ahern