CVE-2017-18218: Use After Free (CWE-416)
value: In drivers/net/ethernet/hisilicon/hns/hns_enet.c in the Linux kernel before 4.13, local users can cause a denial of service (use-after-free and BUG) or possibly have unspecified other impact by leveraging differences in skb handling between hns_nic_net_xmit_hw and hns_nic_net_xmit.
CWE description: The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.
CVSS v3 base score: 7.8
Published: 2018-03-05T20:29Z
Repository: https://github.com/torvalds/linux
Language: C
Files changed: drivers/net/ethernet/hisilicon/hns/hns_enet.c, drivers/net/ethernet/hisilicon/hns/hns_enet.h
Commit date: 2017-07-08 11:05:21 +0100
Commit message: net: hns: Fix a skb used after free bug

skb maybe freed in hns_nic_net_xmit_hw() and return NETDEV_TX_OK,
which cause hns_nic_net_xmit to use a freed skb.

BUG: KASAN: use-after-free in hns_nic_net_xmit_hw+0x62c/0x940...
	[17659.112635]      alloc_debug_processing+0x18c/0x1a0
	[17659.117208]      __slab_alloc+0x52c/0x560
	[17659.120909]      kmem_cache_alloc_node+0xac/0x2c0
	[17659.125309]      __alloc_skb+0x6c/0x260
	[17659.128837]      tcp_send_ack+0x8c/0x280
	[17659.132449]      __tcp_ack_snd_check+0x9c/0xf0
	[17659.136587]      tcp_rcv_established+0x5a4/0xa70
	[17659.140899]      tcp_v4_do_rcv+0x27c/0x620
	[17659.144687]      tcp_prequeue_process+0x108/0x170
	[17659.149085]      tcp_recvmsg+0x940/0x1020
	[17659.152787]      inet_recvmsg+0x124/0x180
	[17659.156488]      sock_recvmsg+0x64/0x80
	[17659.160012]      SyS_recvfrom+0xd8/0x180
	[17659.163626]      __sys_trace_return+0x0/0x4
	[17659.167506] INFO: Freed in kfree_skbmem+0xa0/0xb0 age=23 cpu=1 pid=13
	[17659.174000]      free_debug_processing+0x1d4/0x2c0
	[17659.178486]      __slab_free+0x240/0x390
	[17659.182100]      kmem_cache_free+0x24c/0x270
	[17659.186062]      kfree_skbmem+0xa0/0xb0
	[17659.189587]      __kfree_skb+0x28/0x40
	[17659.193025]      napi_gro_receive+0x168/0x1c0
	[17659.197074]      hns_nic_rx_up_pro+0x58/0x90
	[17659.201038]      hns_nic_rx_poll_one+0x518/0xbc0
	[17659.205352]      hns_nic_common_poll+0x94/0x140
	[17659.209576]      net_rx_action+0x458/0x5e0
	[17659.213363]      __do_softirq+0x1b8/0x480
	[17659.217062]      run_ksoftirqd+0x64/0x80
	[17659.220679]      smpboot_thread_fn+0x224/0x310
	[17659.224821]      kthread+0x150/0x170
	[17659.228084]      ret_from_fork+0x10/0x40

	BUG: KASAN: use-after-free in hns_nic_net_xmit+0x8c/0xc0...
	[17751.080490]      __slab_alloc+0x52c/0x560
	[17751.084188]      kmem_cache_alloc+0x244/0x280
	[17751.088238]      __build_skb+0x40/0x150
	[17751.091764]      build_skb+0x28/0x100
	[17751.095115]      __alloc_rx_skb+0x94/0x150
	[17751.098900]      __napi_alloc_skb+0x34/0x90
	[17751.102776]      hns_nic_rx_poll_one+0x180/0xbc0
	[17751.107097]      hns_nic_common_poll+0x94/0x140
	[17751.111333]      net_rx_action+0x458/0x5e0
	[17751.115123]      __do_softirq+0x1b8/0x480
	[17751.118823]      run_ksoftirqd+0x64/0x80
	[17751.122437]      smpboot_thread_fn+0x224/0x310
	[17751.126575]      kthread+0x150/0x170
	[17751.129838]      ret_from_fork+0x10/0x40
	[17751.133454] INFO: Freed in kfree_skbmem+0xa0/0xb0 age=19 cpu=7 pid=43
	[17751.139951]      free_debug_processing+0x1d4/0x2c0
	[17751.144436]      __slab_free+0x240/0x390
	[17751.148051]      kmem_cache_free+0x24c/0x270
	[17751.152014]      kfree_skbmem+0xa0/0xb0
	[17751.155543]      __kfree_skb+0x28/0x40
	[17751.159022]      napi_gro_receive+0x168/0x1c0
	[17751.163074]      hns_nic_rx_up_pro+0x58/0x90
	[17751.167041]      hns_nic_rx_poll_one+0x518/0xbc0
	[17751.171358]      hns_nic_common_poll+0x94/0x140
	[17751.175585]      net_rx_action+0x458/0x5e0
	[17751.179373]      __do_softirq+0x1b8/0x480
	[17751.183076]      run_ksoftirqd+0x64/0x80
	[17751.186691]      smpboot_thread_fn+0x224/0x310
	[17751.190826]      kthread+0x150/0x170
	[17751.194093]      ret_from_fork+0x10/0x40

Fixes: 13ac695e7ea1 ("net:hns: Add support of Hip06 SoC to the Hislicon Network Subsystem")
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: lipeng <lipeng321@huawei.com>
Reported-by: Jun He <hjat2005@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Diff: diff --git a/drivers/net/ethernet/hisilicon/hns/hns_enet.c b/drivers/net/ethernet/hisilicon/hns/hns_enet.c
index c6700b91a2dfd3..fe166e0f678101 100644
--- a/drivers/net/ethernet/hisilicon/hns/hns_enet.c
+++ b/drivers/net/ethernet/hisilicon/hns/hns_enet.c
@@ -298,13 +298,13 @@ static void fill_tso_desc(struct hnae_ring *ring, void *priv,
 			     (type == DESC_TYPE_SKB && !k) ?
 					DESC_TYPE_SKB : DESC_TYPE_PAGE,
 			     mtu);
 }
 
-int hns_nic_net_xmit_hw(struct net_device *ndev,
-			struct sk_buff *skb,
-			struct hns_nic_ring_data *ring_data)
+netdev_tx_t hns_nic_net_xmit_hw(struct net_device *ndev,
+				struct sk_buff *skb,
+				struct hns_nic_ring_data *ring_data)
 {
 	struct hns_nic_priv *priv = netdev_priv(ndev);
 	struct hnae_ring *ring = ring_data->ring;
 	struct device *dev = ring_to_dev(ring);
 	struct netdev_queue *dev_queue;
@@ -359,10 +359,14 @@ int hns_nic_net_xmit_hw(struct net_device *ndev,
 
 	/*complete translate all packets*/
 	dev_queue = netdev_get_tx_queue(ndev, skb->queue_mapping);
 	netdev_tx_sent_queue(dev_queue, skb->len);
 
+	netif_trans_update(ndev);
+	ndev->stats.tx_bytes += skb->len;
+	ndev->stats.tx_packets++;
+
 	wmb(); /* commit all data before submit */
 	assert(skb->queue_mapping < priv->ae_handle->q_num);
 	hnae_queue_xmit(priv->ae_handle->qs[skb->queue_mapping], buf_num);
 	ring->stats.tx_pkts++;
 	ring->stats.tx_bytes += skb->len;
@@ -1467,21 +1471,15 @@ void hns_nic_poll_controller(struct net_device *ndev)
 
 static netdev_tx_t hns_nic_net_xmit(struct sk_buff *skb,
 				    struct net_device *ndev)
 {
 	struct hns_nic_priv *priv = netdev_priv(ndev);
-	int ret;
 
 	assert(skb->queue_mapping < ndev->ae_handle->q_num);
-	ret = hns_nic_net_xmit_hw(ndev, skb,
-				  &tx_ring_data(priv, skb->queue_mapping));
-	if (ret == NETDEV_TX_OK) {
-		netif_trans_update(ndev);
-		ndev->stats.tx_bytes += skb->len;
-		ndev->stats.tx_packets++;
-	}
-	return (netdev_tx_t)ret;
+
+	return hns_nic_net_xmit_hw(ndev, skb,
+				   &tx_ring_data(priv, skb->queue_mapping));
 }
 
 static void hns_nic_drop_rx_fetch(struct hns_nic_ring_data *ring_data,
 				  struct sk_buff *skb)
 {
diff --git a/drivers/net/ethernet/hisilicon/hns/hns_enet.h b/drivers/net/ethernet/hisilicon/hns/hns_enet.h
index 1b83232082b2a2..9cb4c7884201e1 100644
--- a/drivers/net/ethernet/hisilicon/hns/hns_enet.h
+++ b/drivers/net/ethernet/hisilicon/hns/hns_enet.h
@@ -90,10 +90,10 @@ struct hns_nic_priv {
 
 void hns_ethtool_set_ops(struct net_device *ndev);
 void hns_nic_net_reset(struct net_device *ndev);
 void hns_nic_net_reinit(struct net_device *netdev);
 int hns_nic_init_phy(struct net_device *ndev, struct hnae_handle *h);
-int hns_nic_net_xmit_hw(struct net_device *ndev,
-			struct sk_buff *skb,
-			struct hns_nic_ring_data *ring_data);
+netdev_tx_t hns_nic_net_xmit_hw(struct net_device *ndev,
+				struct sk_buff *skb,
+				struct hns_nic_ring_data *ring_data);
 
 #endif	/**__HNS_ENET_H */

Vulnerable code: int hns_nic_net_xmit_hw(struct net_device *ndev,
			struct sk_buff *skb,
			struct hns_nic_ring_data *ring_data)
	int ret;
	ret = hns_nic_net_xmit_hw(ndev, skb,
				  &tx_ring_data(priv, skb->queue_mapping));
	if (ret == NETDEV_TX_OK) {
		netif_trans_update(ndev);
		ndev->stats.tx_bytes += skb->len;
		ndev->stats.tx_packets++;
	}
	return (netdev_tx_t)ret;
int hns_nic_net_xmit_hw(struct net_device *ndev,
			struct sk_buff *skb,
			struct hns_nic_ring_data *ring_data);
Fixed code: netdev_tx_t hns_nic_net_xmit_hw(struct net_device *ndev,
				struct sk_buff *skb,
				struct hns_nic_ring_data *ring_data)
	netif_trans_update(ndev);
	ndev->stats.tx_bytes += skb->len;
	ndev->stats.tx_packets++;


	return hns_nic_net_xmit_hw(ndev, skb,
				   &tx_ring_data(priv, skb->queue_mapping));
netdev_tx_t hns_nic_net_xmit_hw(struct net_device *ndev,
				struct sk_buff *skb,
				struct hns_nic_ring_data *ring_data);