[PATCH] NETLINK: Infinite recursion in netlink.

[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: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index d47b72af89edeb4a9f506d4f919117de5517d2ae..fa2cb8c2989182cf1d7a6721612ea2936297cc1a 100644 (file)
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -772,6 +772,8 @@ 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();
 
@@ -783,6 +785,7 @@ 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();
        }
@@ -797,6 +800,9 @@ 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))) {
@@ -809,7 +815,7 @@ 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);