This is a note to let you know that I've just added the patch titled
tipc: check minimum bearer MTU
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tipc-check-minimum-bearer-mtu.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 3de81b758853f0b29c61e246679d20b513c4cfec Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Michal=20Kube=C4=8Dek?= <mkubecek@xxxxxxx>
Date: Fri, 2 Dec 2016 09:33:41 +0100
Subject: tipc: check minimum bearer MTU
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From: Michal Kubeček <mkubecek@xxxxxxx>
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: b97bf3fd8f6a ("[TIPC] Initial merge")
Signed-off-by: Michal Kubecek <mkubecek@xxxxxxx>
Reported-by: Qian Zhang (张谦) <zhangqian-c@xxxxxx>
Acked-by: Ying Xue <ying.xue@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
[bwh: Backported to 4.4:
- Adjust context
- NETDEV_GOING_DOWN and NETDEV_CHANGEMTU cases in net notifier were combined]
Signed-off-by: Ben Hutchings <ben.hutchings@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/tipc/bearer.c | 13 +++++++++++--
net/tipc/bearer.h | 13 +++++++++++++
net/tipc/udp_media.c | 5 +++++
3 files changed, 29 insertions(+), 2 deletions(-)
--- a/net/tipc/bearer.c
+++ b/net/tipc/bearer.c
@@ -381,6 +381,10 @@ int tipc_enable_l2_media(struct net *net
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 n
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:
--- a/net/tipc/bearer.h
+++ b/net/tipc/bearer.h
@@ -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, u
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 */
--- a/net/tipc/udp_media.c
+++ b/net/tipc/udp_media.c
@@ -376,6 +376,11 @@ static int tipc_udp_enable(struct net *n
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)
Patches currently in stable-queue which might be from mkubecek@xxxxxxx are
queue-4.4/tipc-check-minimum-bearer-mtu.patch