net: tracepoint of net_dev_xmit sees freed skb and causes panic
Because there is a possibility that skb is kfree_skb()ed and zero cleared
after ndo_start_xmit, we should not see the contents of skb like skb->len and
skb->dev->name after ndo_start_xmit. But trace_net_dev_xmit does that
and causes panic by NULL pointer dereference.
This patch fixes trace_net_dev_xmit not to see the contents of skb directly.
If you want to reproduce this panic,
1. Get tracepoint of net_dev_xmit on
2. Create 2 guests on KVM
2. Make 2 guests use virtio_net
4. Execute netperf from one to another for a long time as a network burden
5. host will panic(It takes about 30 minutes)
Signed-off-by: Koki Sanagi <sanagi.koki@jp.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/trace/events/net.h b/include/trace/events/net.h
index 5f247f5..f99645d 100644
--- a/include/trace/events/net.h
+++ b/include/trace/events/net.h
@@ -12,22 +12,24 @@
TRACE_EVENT(net_dev_xmit,
TP_PROTO(struct sk_buff *skb,
- int rc),
+ int rc,
+ struct net_device *dev,
+ unsigned int skb_len),
- TP_ARGS(skb, rc),
+ TP_ARGS(skb, rc, dev, skb_len),
TP_STRUCT__entry(
__field( void *, skbaddr )
__field( unsigned int, len )
__field( int, rc )
- __string( name, skb->dev->name )
+ __string( name, dev->name )
),
TP_fast_assign(
__entry->skbaddr = skb;
- __entry->len = skb->len;
+ __entry->len = skb_len;
__entry->rc = rc;
- __assign_str(name, skb->dev->name);
+ __assign_str(name, dev->name);
),
TP_printk("dev=%s skbaddr=%p len=%u rc=%d",