@@ -64,7 +64,7 @@ struct rtnl_link_ops {
size_t priv_size;
void (*setup)(struct net_device *dev);
- int maxtype;
+ unsigned int maxtype;
const struct nla_policy *policy;
int (*validate)(struct nlattr *tb[],
struct nlattr *data[],
@@ -92,7 +92,7 @@ struct rtnl_link_ops {
unsigned int (*get_num_tx_queues)(void);
unsigned int (*get_num_rx_queues)(void);
- int slave_maxtype;
+ unsigned int slave_maxtype;
const struct nla_policy *slave_policy;
int (*slave_changelink)(struct net_device *dev,
struct net_device *slave_dev,
@@ -59,6 +59,9 @@
#include <net/rtnetlink.h>
#include <net/net_namespace.h>
+#define RTNL_MAX_TYPE 48
+#define RTNL_SLAVE_MAX_TYPE 36
+
struct rtnl_link {
rtnl_doit_func doit;
rtnl_dumpit_func dumpit;
@@ -389,6 +392,11 @@ int rtnl_link_register(struct rtnl_link_ops *ops)
{
int err;
+ /* Sanity-check max sizes to avoid stack buffer overflow. */
+ if (WARN_ON(ops->maxtype > RTNL_MAX_TYPE ||
+ ops->slave_maxtype > RTNL_SLAVE_MAX_TYPE))
+ return -EINVAL;
+
rtnl_lock();
err = __rtnl_link_register(ops);
rtnl_unlock();
@@ -2900,13 +2908,16 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
}
if (1) {
- struct nlattr *attr[ops ? ops->maxtype + 1 : 1];
- struct nlattr *slave_attr[m_ops ? m_ops->slave_maxtype + 1 : 1];
+ struct nlattr *attr[RTNL_MAX_TYPE + 1];
+ struct nlattr *slave_attr[RTNL_SLAVE_MAX_TYPE + 1];
struct nlattr **data = NULL;
struct nlattr **slave_data = NULL;
struct net *dest_net, *link_net = NULL;
if (ops) {
+ if (ops->maxtype > RTNL_MAX_TYPE)
+ return -EINVAL;
+
if (ops->maxtype && linkinfo[IFLA_INFO_DATA]) {
err = nla_parse_nested(attr, ops->maxtype,
linkinfo[IFLA_INFO_DATA],
@@ -2923,6 +2934,9 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
}
if (m_ops) {
+ if (ops->slave_maxtype > RTNL_SLAVE_MAX_TYPE)
+ return -EINVAL;
+
if (m_ops->slave_maxtype &&
linkinfo[IFLA_INFO_SLAVE_DATA]) {
err = nla_parse_nested(slave_attr,
In the quest to remove all stack VLA usage from the kernel[1], this allocates the maximum size expected for all possible types and adds sanity-checks at both registration and usage to make sure nothing gets out of sync. This matches the proposed VLA solution for nfnetlink[2]. The values chosen here were based on finding assignments for .maxtype and .slave_maxtype and manually counting the enums: slave_maxtype (max 33): IFLA_BRPORT_MAX 33 IFLA_BOND_SLAVE_MAX 9 maxtype (max 45): IFLA_BOND_MAX 28 IFLA_BR_MAX 45 __IFLA_CAIF_HSI_MAX 8 IFLA_CAIF_MAX 4 IFLA_CAN_MAX 16 IFLA_GENEVE_MAX 12 IFLA_GRE_MAX 25 IFLA_GTP_MAX 5 IFLA_HSR_MAX 7 IFLA_IPOIB_MAX 4 IFLA_IPTUN_MAX 21 IFLA_IPVLAN_MAX 3 IFLA_MACSEC_MAX 15 IFLA_MACVLAN_MAX 7 IFLA_PPP_MAX 2 __IFLA_RMNET_MAX 4 IFLA_VLAN_MAX 6 IFLA_VRF_MAX 2 IFLA_VTI_MAX 7 IFLA_VXLAN_MAX 28 VETH_INFO_MAX 2 VXCAN_INFO_MAX 2 This additionally changes maxtype and slave_maxtype fields to unsigned, since they're only ever using positive values. [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com [2] https://patchwork.kernel.org/patch/10439647/ Signed-off-by: Kees Cook <keescook@chromium.org> --- include/net/rtnetlink.h | 4 ++-- net/core/rtnetlink.c | 18 ++++++++++++++++-- 2 files changed, 18 insertions(+), 4 deletions(-)