bonding: validate ip header before check IPPROTO_IGMP

bond_xmit_roundrobin() checks for IGMP packets but it parses
the IP header even before checking skb->protocol.

We should validate the IP header with pskb_may_pull() before
using iph->protocol.

Reported-and-tested-by: syzbot+e5be16aa39ad6e755391@syzkaller.appspotmail.com
Fixes: a2fd940f4cff ("bonding: fix broken multicast with round-robin mode")
Cc: Jay Vosburgh <j.vosburgh@gmail.com>
Cc: Veaceslav Falico <vfalico@gmail.com>
Cc: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: Cong Wang <xiyou.wangcong@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 799fc38c5c34e8d167a7a14d01eff54034a1f86a..b0aab3a0a1bfae86d9a87e98e439bf47c102d124 100644 (file)
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -3866,8 +3866,8 @@ static netdev_tx_t bond_xmit_roundrobin(struct sk_buff *skb,
                                        struct net_device *bond_dev)
 {
        struct bonding *bond = netdev_priv(bond_dev);
-       struct iphdr *iph = ip_hdr(skb);
        struct slave *slave;
+       int slave_cnt;
        u32 slave_id;
 
        /* Start with the curr_active_slave that joined the bond as the
@@ -3876,23 +3876,32 @@ static netdev_tx_t bond_xmit_roundrobin(struct sk_buff *skb,
         * send the join/membership reports.  The curr_active_slave found
         * will send all of this type of traffic.
         */
-       if (iph->protocol == IPPROTO_IGMP && skb->protocol == htons(ETH_P_IP)) {
-               slave = rcu_dereference(bond->curr_active_slave);
-               if (slave)
-                       bond_dev_queue_xmit(bond, skb, slave->dev);
-               else
-                       bond_xmit_slave_id(bond, skb, 0);
-       } else {
-               int slave_cnt = READ_ONCE(bond->slave_cnt);
+       if (skb->protocol == htons(ETH_P_IP)) {
+               int noff = skb_network_offset(skb);
+               struct iphdr *iph;
 
-               if (likely(slave_cnt)) {
-                       slave_id = bond_rr_gen_slave_id(bond);
-                       bond_xmit_slave_id(bond, skb, slave_id % slave_cnt);
-               } else {
-                       bond_tx_drop(bond_dev, skb);
+               if (unlikely(!pskb_may_pull(skb, noff + sizeof(*iph))))
+                       goto non_igmp;
+
+               iph = ip_hdr(skb);
+               if (iph->protocol == IPPROTO_IGMP) {
+                       slave = rcu_dereference(bond->curr_active_slave);
+                       if (slave)
+                               bond_dev_queue_xmit(bond, skb, slave->dev);
+                       else
+                               bond_xmit_slave_id(bond, skb, 0);
+                       return NETDEV_TX_OK;
                }
        }
 
+non_igmp:
+       slave_cnt = READ_ONCE(bond->slave_cnt);
+       if (likely(slave_cnt)) {
+               slave_id = bond_rr_gen_slave_id(bond);
+               bond_xmit_slave_id(bond, skb, slave_id % slave_cnt);
+       } else {
+               bond_tx_drop(bond_dev, skb);
+       }
        return NETDEV_TX_OK;
 }