[NETLINK]: Infinite recursion in netlink (CVE-2007-1861)

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

Sergey Vlasov:
Oops fix

Signed-off-by: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Signed-off-by: Sergey Vlasov <vsu@altlinux.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Adrian Bunk <bunk@stusta.de>

diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 4e3d3811dea29f67c2cd701368ea3bb6a0c677a8..5ca2af0a1c26c8e75c2565ed68708c42da1381ba 100644 (file)
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -525,6 +525,12 @@ static void nl_fib_lookup(struct fib_result_nl *frn, struct fib_table *tb )
                                                            .fwmark = frn->fl_fwmark,
                                                            .tos = frn->fl_tos,
                                                            .scope = frn->fl_scope } } };
+
+#ifdef CONFIG_IP_MULTIPLE_TABLES
+       res.r = NULL;
+#endif
+
+       frn->err = -ENOENT;
        if (tb) {
                local_bh_disable();
 
@@ -536,6 +542,7 @@ 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();
        }
@@ -550,6 +557,9 @@ 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))) {
@@ -562,7 +572,7 @@ 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_pid = pid;
        NETLINK_CB(skb).dst_group = 0;  /* unicast */