Commit 1194ed0a authored by Alexey Kuznetsov's avatar Alexey Kuznetsov Committed by David S. Miller
Browse files

[NETLINK]: Infinite recursion in netlink. 



Reply to NETLINK_FIB_LOOKUP messages were misrouted back to kernel,
which resulted in infinite recursion and stack overflow.

The bug is present in all kernel versions since the feature appeared.

The patch also makes some minimal cleanup:

1. Return something consistent (-ENOENT) when fib table is missing
2. Do not crash when queue is empty (does not happen, but yet)
3. Put result of lookup

Signed-off-by: default avatarAlexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 5044eed4

net/ipv4/fib_frontend.c

+7 −1
Original line number Diff line number Diff line
@@ -776,6 +776,8 @@ static void nl_fib_lookup(struct fib_result_nl *frn, struct fib_table *tb ) 
				       .nl_u = { .ip4_u = { .daddr = frn->fl_addr,

							    .tos = frn->fl_tos,

							    .scope = frn->fl_scope } } };



	frn->err = -ENOENT;

	if (tb) {

		local_bh_disable();
@@ -787,6 +789,7 @@ static void nl_fib_lookup(struct fib_result_nl *frn, struct fib_table *tb ) 
			frn->nh_sel = res.nh_sel;

			frn->type = res.type;

			frn->scope = res.scope;

			fib_res_put(&res);

		}

		local_bh_enable();

	}
@@ -801,6 +804,9 @@ static void nl_fib_input(struct sock *sk, int len) 
	struct fib_table *tb;



	skb = skb_dequeue(&sk->sk_receive_queue);

	if (skb == NULL)

		return;



	nlh = (struct nlmsghdr *)skb->data;

	if (skb->len < NLMSG_SPACE(0) || skb->len < nlh->nlmsg_len ||

	    nlh->nlmsg_len < NLMSG_LENGTH(sizeof(*frn))) {
@@ -813,7 +819,7 @@ static void nl_fib_input(struct sock *sk, int len) 


	nl_fib_lookup(frn, tb);



	pid = nlh->nlmsg_pid;           /*pid of sending process */

	pid = NETLINK_CB(skb).pid;       /* pid of sending process */

	NETLINK_CB(skb).pid = 0;         /* from kernel */

	NETLINK_CB(skb).dst_group = 0;  /* unicast */

	netlink_unicast(sk, skb, pid, MSG_DONTWAIT);

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