bonding: use local function pointer of bond->recv_probe in bond_handle_frame

The bond->recv_probe is called in bond_handle_frame() when
a packet is received, but bond_close() sets it to NULL. So,
a panic occurs when both functions work in parallel.

Why this happen:
After null pointer check of bond->recv_probe, an sk_buff is
duplicated and bond->recv_probe is called in bond_handle_frame.
So, a panic occurs when bond_close() is called between the
check and call of bond->recv_probe.

Patch:
This patch uses a local function pointer of bond->recv_probe
in bond_handle_frame(). So, it can avoid the null pointer
dereference.

Signed-off-by: Mitsuo Hayasaka <mitsuo.hayasaka.hu@hitachi.com>
Cc: Jay Vosburgh <fubar@us.ibm.com>
Cc: Andy Gospodarek <andy@greyhouse.net>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: WANG Cong <xiyou.wangcong@gmail.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 6d79b78cfc75594a8d9398bae83ff08bfe36246f..de3d351ccb6b19bc42c73dc2004a9a586fce20bc 100644 (file)
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -1435,6 +1435,8 @@ static rx_handler_result_t bond_handle_frame(struct sk_buff **pskb)
        struct sk_buff *skb = *pskb;
        struct slave *slave;
        struct bonding *bond;
+       void (*recv_probe)(struct sk_buff *, struct bonding *,
+                               struct slave *);
 
        skb = skb_share_check(skb, GFP_ATOMIC);
        if (unlikely(!skb))
@@ -1448,11 +1450,12 @@ static rx_handler_result_t bond_handle_frame(struct sk_buff **pskb)
        if (bond->params.arp_interval)
                slave->dev->last_rx = jiffies;
 
-       if (bond->recv_probe) {
+       recv_probe = ACCESS_ONCE(bond->recv_probe);
+       if (recv_probe) {
                struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC);
 
                if (likely(nskb)) {
-                       bond->recv_probe(nskb, bond, slave);
+                       recv_probe(nskb, bond, slave);
                        dev_kfree_skb(nskb);
                }
        }