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authorKoki Sanagi <sanagi.koki@jp.fujitsu.com>2011-05-30 21:48:34 +0000
committerDavid S. Miller <davem@davemloft.net>2011-06-02 14:06:31 -0700
commitec764bf083a6ff396234351b51fd236f53c903bf (patch)
tree30c0f8232fe10c76651114dea999b93fa2c8ade5
parent2e4ceec4edaef6e903422792de4f7f37de98cec6 (diff)
downloadlinux-stericsson-ec764bf083a6ff396234351b51fd236f53c903bf.tar.gz
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>
-rw-r--r--include/trace/events/net.h12
-rw-r--r--net/core/dev.c7
2 files changed, 12 insertions, 7 deletions
diff --git a/include/trace/events/net.h b/include/trace/events/net.h
index 5f247f5ffc56..f99645d05a8f 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",
diff --git a/net/core/dev.c b/net/core/dev.c
index c7e305d13b71..939307891e71 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2096,6 +2096,7 @@ int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
{
const struct net_device_ops *ops = dev->netdev_ops;
int rc = NETDEV_TX_OK;
+ unsigned int skb_len;
if (likely(!skb->next)) {
u32 features;
@@ -2146,8 +2147,9 @@ int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
}
}
+ skb_len = skb->len;
rc = ops->ndo_start_xmit(skb, dev);
- trace_net_dev_xmit(skb, rc);
+ trace_net_dev_xmit(skb, rc, dev, skb_len);
if (rc == NETDEV_TX_OK)
txq_trans_update(txq);
return rc;
@@ -2167,8 +2169,9 @@ gso:
if (dev->priv_flags & IFF_XMIT_DST_RELEASE)
skb_dst_drop(nskb);
+ skb_len = nskb->len;
rc = ops->ndo_start_xmit(nskb, dev);
- trace_net_dev_xmit(nskb, rc);
+ trace_net_dev_xmit(nskb, rc, dev, skb_len);
if (unlikely(rc != NETDEV_TX_OK)) {
if (rc & ~NETDEV_TX_MASK)
goto out_kfree_gso_skb;