ipv4: validate IPV4_DEVCONF attributes properly

As the IPV4_DEVCONF netlink attributes are not being validated, it is
possible to use netlink to set read-only values like mc_forwarding. In
addition, valid ranges are not being validated neither but that is less
relevant as they aren't in sysctl.

To avoid similar situations in the future, define a NLA policy for
IPV4_DEVCONF attributes which are nested in IFLA_INET_CONF.

Signed-off-by: Fernando Fernandez Mancera <fmancera@suse.de>
Link: https://patch.msgid.link/20260312142637.5704-1-fmancera@suse.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 537bb6c315d2e25916984623e7e28169b9fa9196..58fe7cb69545c927f7b4bd7de9d9569335a5e9fd 100644 (file)
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -2063,12 +2063,50 @@ static const struct nla_policy inet_af_policy[IFLA_INET_MAX+1] = {
        [IFLA_INET_CONF]        = { .type = NLA_NESTED },
 };
 
+static const struct nla_policy inet_devconf_policy[IPV4_DEVCONF_MAX + 1] = {
+       [IPV4_DEVCONF_FORWARDING]       = NLA_POLICY_RANGE(NLA_U32, 0, 1),
+       [IPV4_DEVCONF_MC_FORWARDING]    = { .type = NLA_REJECT },
+       [IPV4_DEVCONF_PROXY_ARP]        = NLA_POLICY_RANGE(NLA_U32, 0, 1),
+       [IPV4_DEVCONF_ACCEPT_REDIRECTS] = NLA_POLICY_RANGE(NLA_U32, 0, 1),
+       [IPV4_DEVCONF_SECURE_REDIRECTS] = NLA_POLICY_RANGE(NLA_U32, 0, 1),
+       [IPV4_DEVCONF_SEND_REDIRECTS]   = NLA_POLICY_RANGE(NLA_U32, 0, 1),
+       [IPV4_DEVCONF_SHARED_MEDIA]     = NLA_POLICY_RANGE(NLA_U32, 0, 1),
+       [IPV4_DEVCONF_RP_FILTER]        = NLA_POLICY_RANGE(NLA_U32, 0, 2),
+       [IPV4_DEVCONF_ACCEPT_SOURCE_ROUTE] = NLA_POLICY_RANGE(NLA_U32, 0, 1),
+       [IPV4_DEVCONF_BOOTP_RELAY]      = NLA_POLICY_RANGE(NLA_U32, 0, 1),
+       [IPV4_DEVCONF_LOG_MARTIANS]     = NLA_POLICY_RANGE(NLA_U32, 0, 1),
+       [IPV4_DEVCONF_TAG]              = { .type = NLA_U32 },
+       [IPV4_DEVCONF_ARPFILTER]        = NLA_POLICY_RANGE(NLA_U32, 0, 1),
+       [IPV4_DEVCONF_MEDIUM_ID]        = NLA_POLICY_MIN(NLA_S32, -1),
+       [IPV4_DEVCONF_NOXFRM]           = NLA_POLICY_RANGE(NLA_U32, 0, 1),
+       [IPV4_DEVCONF_NOPOLICY]         = NLA_POLICY_RANGE(NLA_U32, 0, 1),
+       [IPV4_DEVCONF_FORCE_IGMP_VERSION] = NLA_POLICY_RANGE(NLA_U32, 0, 3),
+       [IPV4_DEVCONF_ARP_ANNOUNCE]     = NLA_POLICY_RANGE(NLA_U32, 0, 2),
+       [IPV4_DEVCONF_ARP_IGNORE]       = NLA_POLICY_RANGE(NLA_U32, 0, 8),
+       [IPV4_DEVCONF_PROMOTE_SECONDARIES] = NLA_POLICY_RANGE(NLA_U32, 0, 1),
+       [IPV4_DEVCONF_ARP_ACCEPT]       = NLA_POLICY_RANGE(NLA_U32, 0, 2),
+       [IPV4_DEVCONF_ARP_NOTIFY]       = NLA_POLICY_RANGE(NLA_U32, 0, 1),
+       [IPV4_DEVCONF_ACCEPT_LOCAL]     = NLA_POLICY_RANGE(NLA_U32, 0, 1),
+       [IPV4_DEVCONF_SRC_VMARK]        = NLA_POLICY_RANGE(NLA_U32, 0, 1),
+       [IPV4_DEVCONF_PROXY_ARP_PVLAN]  = NLA_POLICY_RANGE(NLA_U32, 0, 1),
+       [IPV4_DEVCONF_ROUTE_LOCALNET]   = NLA_POLICY_RANGE(NLA_U32, 0, 1),
+       [IPV4_DEVCONF_BC_FORWARDING]    = NLA_POLICY_RANGE(NLA_U32, 0, 1),
+       [IPV4_DEVCONF_IGMPV2_UNSOLICITED_REPORT_INTERVAL] = { .type = NLA_U32 },
+       [IPV4_DEVCONF_IGMPV3_UNSOLICITED_REPORT_INTERVAL] = { .type = NLA_U32 },
+       [IPV4_DEVCONF_IGNORE_ROUTES_WITH_LINKDOWN] =
+               NLA_POLICY_RANGE(NLA_U32, 0, 1),
+       [IPV4_DEVCONF_DROP_UNICAST_IN_L2_MULTICAST] =
+               NLA_POLICY_RANGE(NLA_U32, 0, 1),
+       [IPV4_DEVCONF_DROP_GRATUITOUS_ARP] = NLA_POLICY_RANGE(NLA_U32, 0, 1),
+       [IPV4_DEVCONF_ARP_EVICT_NOCARRIER] = NLA_POLICY_RANGE(NLA_U32, 0, 1),
+};
+
 static int inet_validate_link_af(const struct net_device *dev,
                                 const struct nlattr *nla,
                                 struct netlink_ext_ack *extack)
 {
-       struct nlattr *a, *tb[IFLA_INET_MAX+1];
-       int err, rem;
+       struct nlattr *tb[IFLA_INET_MAX + 1], *nested_tb[IPV4_DEVCONF_MAX + 1];
+       int err;
 
        if (dev && !__in_dev_get_rtnl(dev))
                return -EAFNOSUPPORT;
@@ -2079,15 +2117,12 @@ static int inet_validate_link_af(const struct net_device *dev,
                return err;
 
        if (tb[IFLA_INET_CONF]) {
-               nla_for_each_nested(a, tb[IFLA_INET_CONF], rem) {
-                       int cfgid = nla_type(a);
+               err = nla_parse_nested(nested_tb, IPV4_DEVCONF_MAX,
+                                      tb[IFLA_INET_CONF], inet_devconf_policy,
+                                      extack);
 
-                       if (nla_len(a) < 4)
-                               return -EINVAL;
-
-                       if (cfgid <= 0 || cfgid > IPV4_DEVCONF_MAX)
-                               return -EINVAL;
-               }
+               if (err < 0)
+                       return err;
        }
 
        return 0;