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Thu, 12 Mar 2026 14:26:46 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 1DnLFybNsmkUdAAAD6G6ig (envelope-from ); Thu, 12 Mar 2026 14:26:46 +0000 From: Fernando Fernandez Mancera To: netdev@vger.kernel.org Cc: horms@kernel.org, pabeni@redhat.com, kuba@kernel.org, edumazet@google.com, dsahern@kernel.org, davem@davemloft.net, Fernando Fernandez Mancera Subject: [PATCH net-next v4] ipv4: validate IPV4_DEVCONF attributes properly Date: Thu, 12 Mar 2026 15:26:37 +0100 Message-ID: <20260312142637.5704-1-fmancera@suse.de> X-Mailer: git-send-email 2.51.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spamd-Result: default: False [-3.01 / 50.00]; BAYES_HAM(-3.00)[100.00%]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_MISSING_CHARSET(0.50)[]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:mid,suse.de:dkim,suse.de:email,imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; MIME_TRACE(0.00)[0:+]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; RCPT_COUNT_SEVEN(0.00)[8]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; RCVD_TLS_ALL(0.00)[]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; DKIM_TRACE(0.00)[suse.de:+] X-Rspamd-Action: no action X-Spam-Flag: NO X-Spam-Score: -3.01 X-Spam-Level: X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Rspamd-Queue-Id: EBA6E4D1FA 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 --- v2: no changes v3: dropped the fixes tag and adjusted the indentation of the policy, MEDIUM_ID is now NLA_S32 v4: used NLA_POLICY_MIN() for MEDIUM_ID so the min value takes effect properly, make ARP_ACCEPT accept 2 as valid value and checked each attribute again so they match the documentation. Tested with a custom script using libnl --- net/ipv4/devinet.c | 55 +++++++++++++++++++++++++++++++++++++--------- 1 file changed, 45 insertions(+), 10 deletions(-) diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c index 537bb6c315d2..58fe7cb69545 100644 --- 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; -- 2.53.0