[AF_NETLINK]: Fix DoS in netlink_rcv_skb()

From: Martin Murray <murrayma@citi.umich.edu>

Sanity check nlmsg_len during netlink_rcv_skb.  An nlmsg_len == 0 can
cause infinite loop in kernel, effectively DoSing machine.  Noted by
Matin Murray.

Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index a67f1b44c9a385e24c1b8c3330e2e869b2e5d55b..bb50c8a9fcad51b4539e5866a2ce10a427a14d70 100644 (file)
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1422,7 +1422,7 @@ static int netlink_rcv_skb(struct sk_buff *skb, int (*cb)(struct sk_buff *,
        while (skb->len >= nlmsg_total_size(0)) {
                nlh = (struct nlmsghdr *) skb->data;
 
-               if (skb->len < nlh->nlmsg_len)
+               if (nlh->nlmsg_len < NLMSG_HDRLEN || skb->len < nlh->nlmsg_len)
                        return 0;
 
                total_len = min(NLMSG_ALIGN(nlh->nlmsg_len), skb->len);