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netvsc: add rcu_read locking to netvsc callback

PATCH In review Stephen Hemminger 2 participants 2 messages Jan 11, 2017

Subsystems (3)
Networking Network drivers Hyper-V/Azure core and drivers
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Stephen Hemminger

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#0 lore raw

PATCH v2 1/1 netvsc: add rcu_read locking to netvsc callback

The receive callback (in tasklet context) is using RCU to get reference to associated VF network device but this is not safe. RCU read lock needs to be held. Found by running with full lockdep debugging enabled.

Fixes f207c10d9823 ("hv_netvsc: use RCU to protect vf_netdev")
Signed-off-by Stephen Hemminger <[email protected]>

---
v2 - fix commit message

 drivers/net/hyperv/netvsc_drv.c | 3 +++
 1 file changed, 3 insertions(+)
drivers/net/hyperv/netvsc_drv.c +3 -0
index c9414c054852..fcab8019dda0 100644
@@ -659,6 +659,7 @@ int netvsc_recv_callback(struct hv_device *device_obj,
 	 * policy filters on the host). Deliver these via the VF
 	 * interface in the guest.
 	 */
+	rcu_read_lock();
 	vf_netdev = rcu_dereference(net_device_ctx->vf_netdev);
 	if (vf_netdev && (vf_netdev->flags & IFF_UP))
 		net = vf_netdev;

@@ -667,6 +668,7 @@ int netvsc_recv_callback(struct hv_device *device_obj,
 	skb = netvsc_alloc_recv_skb(net, packet, csum_info, *data, vlan_tci);
 	if (unlikely(!skb)) {
 		++net->stats.rx_dropped;
+		rcu_read_unlock();
 		return NVSP_STAT_FAIL;
 	}
 

@@ -696,6 +698,7 @@ int netvsc_recv_callback(struct hv_device *device_obj,
 	 * TODO - use NAPI?
 	 */
 	netif_rx(skb);
+	rcu_read_unlock();
 
 	return 0;
 }
Signature · 1 line
2.11.0
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#1 lore raw

From: Stephen Hemminger <[email protected]>
Date: Wed, 11 Jan 2017 09:16:32 -0800

Quoted 9 lines

The receive callback (in tasklet context) is using RCU to get reference to associated VF network device but this is not safe. RCU read lock needs to be held. Found by running with full lockdep debugging enabled.

Fixes f207c10d9823 ("hv_netvsc: use RCU to protect vf_netdev")
Signed-off-by Stephen Hemminger <[email protected]>

---
v2 - fix commit message

Applied and queued up for -stable.