From 3de81b758853f0b29c61e246679d20b513c4cfec Mon Sep 17 00:00:00 2001 From: Michal Kubeček Date: Fri, 2 Dec 2016 09:33:41 +0100 Subject: tipc: check minimum bearer MTU MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Reported-by: Qian Zhang (张谦) Acked-by: Ying Xue Signed-off-by: David S. Miller --- net/tipc/bearer.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'net/tipc/bearer.h') diff --git a/net/tipc/bearer.h b/net/tipc/bearer.h index 78892e2f53e3..278ff7f616f9 100644 --- a/net/tipc/bearer.h +++ b/net/tipc/bearer.h @@ -39,6 +39,7 @@ #include "netlink.h" #include "core.h" +#include "msg.h" #include #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 */ -- cgit v1.2.3