Commit 016d0298 authored by Michal Kubeček's avatar Michal Kubeček Committed by Sasha Levin

tipc: check minimum bearer MTU

[ Upstream commit 3de81b75 ]

Qian Zhang (张谦) reported a potential socket buffer overflow in
tipc_msg_build() which is also known as CVE-2016-8632: due to
insufficient checks, a buffer overflow can occur if MTU is too short for
even tipc headers. As anyone can set device MTU in a user/net namespace,
this issue can be abused by a regular user.

As agreed in the discussion on Ben Hutchings' original patch, we should
check the MTU at the moment a bearer is attached rather than for each
processed packet. We also need to repeat the check when bearer MTU is
adjusted to new device MTU. UDP case also needs a check to avoid
overflow when calculating bearer MTU.

References: CVE-2016-8632
Fixes: b97bf3fd ("[TIPC] Initial merge")
Signed-off-by: default avatarMichal Kubecek <mkubecek@suse.cz>
Reported-by: default avatarQian Zhang (张谦) <zhangqian-c@360.cn>
Acked-by: default avatarYing Xue <ying.xue@windriver.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>

Conflicts:
	net/tipc/bearer.c
	net/tipc/bearer.h
due to 1a90632d: tipc: eliminate remnants of hungarian notation
and b1c29f6b tipc: simplify resetting and disabling of bearers
Signed-off-by: default avatarPhilipp Hahn <hahn@univention.de>
Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
parent efcf38bd
......@@ -386,6 +386,10 @@ int tipc_enable_l2_media(struct net *net, struct tipc_bearer *b,
dev = dev_get_by_name(net, driver_name);
if (!dev)
return -ENODEV;
if (tipc_mtu_bad(dev, 0)) {
dev_put(dev);
return -EINVAL;
}
/* Associate TIPC bearer with L2 bearer */
rcu_assign_pointer(b->media_ptr, dev);
......@@ -524,14 +528,17 @@ static int tipc_l2_device_event(struct notifier_block *nb, unsigned long evt,
if (!b_ptr)
return NOTIFY_DONE;
b_ptr->mtu = dev->mtu;
switch (evt) {
case NETDEV_CHANGE:
if (netif_carrier_ok(dev))
break;
case NETDEV_DOWN:
case NETDEV_CHANGEMTU:
if (tipc_mtu_bad(dev, 0)) {
bearer_disable(net, b_ptr, false);
break;
}
b_ptr->mtu = dev->mtu;
tipc_reset_bearer(net, b_ptr);
break;
case NETDEV_CHANGEADDR:
......
......@@ -38,6 +38,7 @@
#define _TIPC_BEARER_H
#include "netlink.h"
#include "msg.h"
#include <net/genetlink.h>
#define MAX_BEARERS 2
......@@ -61,6 +62,9 @@
#define TIPC_MEDIA_TYPE_IB 2
#define TIPC_MEDIA_TYPE_UDP 3
/* minimum bearer MTU */
#define TIPC_MIN_BEARER_MTU (MAX_H_SIZE + INT_H_SIZE)
/**
* struct tipc_node_map - set of node identifiers
* @count: # of nodes in set
......@@ -218,4 +222,13 @@ void tipc_bearer_stop(struct net *net);
void tipc_bearer_send(struct net *net, u32 bearer_id, struct sk_buff *buf,
struct tipc_media_addr *dest);
/* check if device MTU is too low for tipc headers */
static inline bool tipc_mtu_bad(struct net_device *dev, unsigned int reserve)
{
if (dev->mtu >= TIPC_MIN_BEARER_MTU + reserve)
return false;
netdev_warn(dev, "MTU too low for tipc bearer\n");
return true;
}
#endif /* _TIPC_BEARER_H */
......@@ -374,6 +374,11 @@ static int tipc_udp_enable(struct net *net, struct tipc_bearer *b,
udp_conf.local_ip.s_addr = htonl(INADDR_ANY);
udp_conf.use_udp_checksums = false;
ub->ifindex = dev->ifindex;
if (tipc_mtu_bad(dev, sizeof(struct iphdr) +
sizeof(struct udphdr))) {
err = -EINVAL;
goto err;
}
b->mtu = dev->mtu - sizeof(struct iphdr)
- sizeof(struct udphdr);
#if IS_ENABLED(CONFIG_IPV6)
......
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