netrom: fix locking in nr_find_socket()

[ Upstream commit 7314f5480f3e37e570104dc5e0f28823ef849e72 ]

nr_find_socket(), nr_find_peer() and nr_find_listener() lock the
sock after finding it in the global list. However, the call path
requires BH disabled for the sock lock consistently.

Actually the locking is unnecessary at this point, we can just hold
the sock refcnt to make sure it is not gone after we unlock the global
list, and lock it later only when needed.

Reported-and-tested-by: syzbot+f621cda8b7e598908efa@syzkaller.appspotmail.com
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/netrom/af_netrom.c b/net/netrom/af_netrom.c
index 1b06a1fcf3e80acfe26a67e31dec1648ce6104f5..ab8b227e0ec0218dc8c11094c292c49fe6126fe3 100644 (file)
--- a/net/netrom/af_netrom.c
+++ b/net/netrom/af_netrom.c
@@ -153,7 +153,7 @@ static struct sock *nr_find_listener(ax25_address *addr)
        sk_for_each(s, &nr_list)
                if (!ax25cmp(&nr_sk(s)->source_addr, addr) &&
                    s->sk_state == TCP_LISTEN) {
-                       bh_lock_sock(s);
+                       sock_hold(s);
                        goto found;
                }
        s = NULL;
@@ -174,7 +174,7 @@ static struct sock *nr_find_socket(unsigned char index, unsigned char id)
                struct nr_sock *nr = nr_sk(s);
 
                if (nr->my_index == index && nr->my_id == id) {
-                       bh_lock_sock(s);
+                       sock_hold(s);
                        goto found;
                }
        }
@@ -198,7 +198,7 @@ static struct sock *nr_find_peer(unsigned char index, unsigned char id,
 
                if (nr->your_index == index && nr->your_id == id &&
                    !ax25cmp(&nr->dest_addr, dest)) {
-                       bh_lock_sock(s);
+                       sock_hold(s);
                        goto found;
                }
        }
@@ -224,7 +224,7 @@ static unsigned short nr_find_next_circuit(void)
                if (i != 0 && j != 0) {
                        if ((sk=nr_find_socket(i, j)) == NULL)
                                break;
-                       bh_unlock_sock(sk);
+                       sock_put(sk);
                }
 
                id++;
@@ -918,6 +918,7 @@ int nr_rx_frame(struct sk_buff *skb, struct net_device *dev)
        }
 
        if (sk != NULL) {
+               bh_lock_sock(sk);
                skb_reset_transport_header(skb);
 
                if (frametype == NR_CONNACK && skb->len == 22)
@@ -927,6 +928,7 @@ int nr_rx_frame(struct sk_buff *skb, struct net_device *dev)
 
                ret = nr_process_rx_frame(sk, skb);
                bh_unlock_sock(sk);
+               sock_put(sk);
                return ret;
        }
 
@@ -958,10 +960,12 @@ int nr_rx_frame(struct sk_buff *skb, struct net_device *dev)
            (make = nr_make_new(sk)) == NULL) {
                nr_transmit_refusal(skb, 0);
                if (sk)
-                       bh_unlock_sock(sk);
+                       sock_put(sk);
                return 0;
        }
 
+       bh_lock_sock(sk);
+
        window = skb->data[20];
 
        skb->sk             = make;
@@ -1014,6 +1018,7 @@ int nr_rx_frame(struct sk_buff *skb, struct net_device *dev)
                sk->sk_data_ready(sk);
 
        bh_unlock_sock(sk);
+       sock_put(sk);
 
        nr_insert_socket(make);