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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Jay Vosburgh <j.vosburgh@gmail.com>,
        Veaceslav Falico <vfalico@gmail.com>,
        Andy Gospodarek <andy@greyhouse.net>,
        Cong Wang <xiyou.wangcong@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <sashal@kernel.org>,
        syzbot+e5be16aa39ad6e755391@syzkaller.appspotmail.com
Subject: [PATCH 5.2 221/413] bonding: validate ip header before check IPPROTO_IGMP
Date:   Wed, 24 Jul 2019 21:18:32 +0200
Message-Id: <20190724191750.592371357@linuxfoundation.org>
In-Reply-To: <20190724191735.096702571@linuxfoundation.org>
References: <20190724191735.096702571@linuxfoundation.org>
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[ Upstream commit 9d1bc24b52fb8c5d859f9a47084bf1179470e04c ]

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: Sasha Levin <sashal@kernel.org>
---
 drivers/net/bonding/bond_main.c | 37 ++++++++++++++++++++-------------
 1 file changed, 23 insertions(+), 14 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 799fc38c5c34..b0aab3a0a1bf 100644
--- 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;
 }
 
-- 
2.20.1