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Commit 65d30f75 authored by Michal Kubeček's avatar Michal Kubeček Committed by Greg Kroah-Hartman
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tipc: check minimum bearer MTU 



commit 3de81b758853f0b29c61e246679d20b513c4cfec upstream.

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: 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>
[bwh: Backported to 4.4:
 - Adjust context
 - NETDEV_GOING_DOWN and NETDEV_CHANGEMTU cases in net notifier were combined]
Signed-off-by: default avatarBen Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 9540baad

net/tipc/bearer.c

+11 −2
Original line number Diff line number Diff line
@@ -381,6 +381,10 @@ 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);
@@ -570,14 +574,19 @@ 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_GOING_DOWN:

		tipc_reset_bearer(net, b_ptr);

		break;

	case NETDEV_CHANGEMTU:

		if (tipc_mtu_bad(dev, 0)) {

			bearer_disable(net, b_ptr);

			break;

		}

		b_ptr->mtu = dev->mtu;

		tipc_reset_bearer(net, b_ptr);

		break;

	case NETDEV_CHANGEADDR:

net/tipc/bearer.h

+13 −0
Original line number Diff line number Diff line
@@ -39,6 +39,7 @@ 


#include "netlink.h"

#include "core.h"

#include "msg.h"

#include <net/genetlink.h>



#define MAX_MEDIA	3
@@ -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
@@ -226,4 +230,13 @@ 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 */

net/tipc/udp_media.c

+5 −0
Original line number Diff line number Diff line
@@ -376,6 +376,11 @@ 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)