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tipc: check minimum bearer MTU

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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.

Fixes: b97bf3fd8f ("[TIPC] Initial merge")
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Reported-by: Qian Zhang (张谦) <zhangqian-c@360.cn>
Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Michal Kubeček 2016-12-02 09:33:41 +01:00 committed by David S. Miller
parent f0d21e8947
commit 3de81b7588
3 changed files with 27 additions and 2 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

11
net/tipc/bearer.c
View file

@ -421,6 +421,10 @@ 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);
@ -610,8 +614,6 @@ static int tipc_l2_device_event(struct notifier_block *nb, unsigned long evt,
if (!b)
return NOTIFY_DONE;
b->mtu = dev->mtu;
switch (evt) {
case NETDEV_CHANGE:
if (netif_carrier_ok(dev))
@ -624,6 +626,11 @@ static int tipc_l2_device_event(struct notifier_block *nb, unsigned long evt,
tipc_reset_bearer(net, b);
break;
case NETDEV_CHANGEMTU:
if (tipc_mtu_bad(dev, 0)) {
bearer_disable(net, b);
break;
}
b->mtu = dev->mtu;
tipc_reset_bearer(net, b);
break;
case NETDEV_CHANGEADDR:

13
net/tipc/bearer.h
View file

@ -39,6 +39,7 @@
#include "netlink.h"
#include "core.h"
#include "msg.h"
#include <net/genetlink.h>
#define MAX_MEDIA 3
@ -59,6 +60,9 @@
#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_media_addr - destination address used by TIPC bearers
* @value: address info (format defined by media)
@ -215,4 +219,13 @@ void tipc_bearer_xmit(struct net *net, u32 bearer_id,
void tipc_bearer_bc_xmit(struct net *net, u32 bearer_id,
struct sk_buff_head *xmitq);
/* 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 */

5
net/tipc/udp_media.c
View file

@ -697,6 +697,11 @@ 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)