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Commit ccf8dbcd authored by Kees Cook's avatar Kees Cook Committed by David S. Miller
Browse files

rtnetlink: Remove VLA usage 

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: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 7bb8c996

include/net/rtnetlink.h

+2 −2
Original line number Diff line number Diff line
@@ -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,

net/core/rtnetlink.c

+16 −2
Original line number Diff line number Diff line
@@ -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();
@@ -2902,13 +2910,16 @@ 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],
@@ -2925,6 +2936,9 @@ 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,