From: Cong Wang <xiyou.wangcong@gmail.com>
Date: Mon, 1 Jul 2019 20:40:24 -0700
Subject: bonding: validate ip header before check IPPROTO_IGMP
Git-commit: 9d1bc24b52fb8c5d859f9a47084bf1179470e04c
Patch-mainline: 5.3-rc1
References: networking-stable-19_07_25

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>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/net/bonding/bond_main.c |   37 +++++++++++++++++++++++--------------
 1 file changed, 23 insertions(+), 14 deletions(-)

--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -3808,8 +3808,8 @@ static u32 bond_rr_gen_slave_id(struct b
 static int 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
@@ -3818,23 +3818,32 @@ static int bond_xmit_roundrobin(struct s
 	 * 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 (unlikely(!pskb_may_pull(skb, noff + sizeof(*iph))))
+			goto non_igmp;
 
-		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);
+		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;
 }