netdev - [PATCH net v2] ipvlan: fix crash when master is set in loopback mode

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Date:   Sun, 18 Dec 2016 11:00:25 -0800
From:   Mahesh Bandewar <mahesh@...dewar.net>
To:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        David Miller <davem@...emloft.net>
Cc:     Mahesh Bandewar <maheshb@...gle.com>
Subject: [PATCH net v2] ipvlan: fix crash when master is set in loopback mode

From: Mahesh Bandewar <maheshb@...gle.com>

In an IPvlan setup when master is set in loopback mode e.g.

  ethtool -K eth0 set loopback on

  where eth0 is master device for IPvlan setup.

The failure actually happens while processing mulitcast packets
but that's a result of unconditionally queueing packets without
ensuring ether-header is part of the linear part of skb.

This patch forces this check at the reception and drops packets
which fail this check before queuing them.

------------[ cut here ]------------
kernel BUG at include/linux/skbuff.h:1737!
Call Trace:
 [<ffffffff921fbbc2>] dev_forward_skb+0x92/0xd0
 [<ffffffffc031ac65>] ipvlan_process_multicast+0x395/0x4c0 [ipvlan]
 [<ffffffffc031a9a7>] ? ipvlan_process_multicast+0xd7/0x4c0 [ipvlan]
 [<ffffffff91cdfea7>] ? process_one_work+0x147/0x660
 [<ffffffff91cdff09>] process_one_work+0x1a9/0x660
 [<ffffffff91cdfea7>] ? process_one_work+0x147/0x660
 [<ffffffff91ce086d>] worker_thread+0x11d/0x360
 [<ffffffff91ce0750>] ? rescuer_thread+0x350/0x350
 [<ffffffff91ce960b>] kthread+0xdb/0xe0
 [<ffffffff91c05c70>] ? _raw_spin_unlock_irq+0x30/0x50
 [<ffffffff91ce9530>] ? flush_kthread_worker+0xc0/0xc0
 [<ffffffff92348b7a>] ret_from_fork+0x9a/0xd0
 [<ffffffff91ce9530>] ? flush_kthread_worker+0xc0/0xc0

Signed-off-by: Mahesh Bandewar <maheshb@...gle.com>
---
v1->v2: commit log update

 drivers/net/ipvlan/ipvlan_core.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/ipvlan/ipvlan_core.c b/drivers/net/ipvlan/ipvlan_core.c
index b4e990743e1d..4294fc1f5564 100644
--- a/drivers/net/ipvlan/ipvlan_core.c
+++ b/drivers/net/ipvlan/ipvlan_core.c
@@ -660,6 +660,9 @@ rx_handler_result_t ipvlan_handle_frame(struct sk_buff **pskb)
 	if (!port)
 		return RX_HANDLER_PASS;
 
+	if (unlikely(!pskb_may_pull(skb, sizeof(struct ethhdr))))
+		goto out;
+
 	switch (port->mode) {
 	case IPVLAN_MODE_L2:
 		return ipvlan_handle_mode_l2(pskb, port);
@@ -672,6 +675,8 @@ rx_handler_result_t ipvlan_handle_frame(struct sk_buff **pskb)
 	/* Should not reach here */
 	WARN_ONCE(true, "ipvlan_handle_frame() called for mode = [%hx]\n",
 			  port->mode);
+
+out:
 	kfree_skb(skb);
 	return RX_HANDLER_CONSUMED;
 }
-- 
2.8.0.rc3.226.g39d4020