From ec764bf083a6ff396234351b51fd236f53c903bf Mon Sep 17 00:00:00 2001 From: Koki Sanagi Date: Mon, 30 May 2011 21:48:34 +0000 Subject: 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 Signed-off-by: David S. Miller --- net/core/dev.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'net/core') diff --git a/net/core/dev.c b/net/core/dev.c index c7e305d13b7..939307891e7 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; -- cgit v1.2.3