lkml.org 
[lkml]   [2018]   [May]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH] 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: Kees Cook <keescook@chromium.org>
---
include/net/rtnetlink.h | 4 ++--
net/core/rtnetlink.c | 18 ++++++++++++++++--
2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/include/net/rtnetlink.h b/include/net/rtnetlink.h
index 14b6b3af8918..0bbaa5488423 100644
--- a/include/net/rtnetlink.h
+++ b/include/net/rtnetlink.h
@@ -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,
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 45936922d7e2..4ede33719ca9 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -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,
--
2.17.0

--
Kees Cook
Pixel Security

\
 
 \ /
  Last update: 2018-05-31 00:21    [W:0.055 / U:7.232 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site