[PATCH 4.9 133/223] ipv4: dont set IPv6 only flags to IPv4 addresses

Greg Kroah-Hartman
2019-08-02T09:49:44Z

From: Matteo Croce <mcroce@redhat.com>

[ Upstream commit 2e60546368165c2449564d71f6005dda9205b5fb ]

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: <BROADCAST,NOARP,UP,LOWER_UP> 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: <BROADCAST,NOARP,UP,LOWER_UP> 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 <mcroce@redhat.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv4/devinet.c | 8 ++++++++
1 file changed, 8 insertions(+)

--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -67,6 +67,11 @@

#include "fib_lookup.h"

+#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,
@@ -453,6 +458,9 @@ static int __inet_insert_ifa(struct in_i
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) &&