From 676d23690fb62b5d51ba5d659935e9f7d9da9f8e Mon Sep 17 00:00:00 2001 From: "David S. Miller" Date: Fri, 11 Apr 2014 16:15:36 -0400 Subject: net: Fix use after free by removing length arg from sk_data_ready callbacks. Several spots in the kernel perform a sequence like: skb_queue_tail(&sk->s_receive_queue, skb); sk->sk_data_ready(sk, skb->len); But at the moment we place the SKB onto the socket receive queue it can be consumed and freed up. So this skb->len access is potentially to freed up memory. Furthermore, the skb->len can be modified by the consumer so it is possible that the value isn't accurate. And finally, no actual implementation of this callback actually uses the length argument. And since nobody actually cared about it's value, lots of call sites pass arbitrary values in such as '0' and even '1'. So just remove the length argument from the callback, that way there is no confusion whatsoever and all of these use-after-free cases get fixed as a side effect. Based upon a patch by Eric Dumazet and his suggestion to audit this issue tree-wide. Signed-off-by: David S. Miller --- net/packet/af_packet.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'net/packet') diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 72e0c71fb01d..b85c67ccb797 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1848,7 +1848,7 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev, skb->dropcount = atomic_read(&sk->sk_drops); __skb_queue_tail(&sk->sk_receive_queue, skb); spin_unlock(&sk->sk_receive_queue.lock); - sk->sk_data_ready(sk, skb->len); + sk->sk_data_ready(sk); return 0; drop_n_acct: @@ -2054,7 +2054,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev, else prb_clear_blk_fill_status(&po->rx_ring); - sk->sk_data_ready(sk, 0); + sk->sk_data_ready(sk); drop_n_restore: if (skb_head != skb->data && skb_shared(skb)) { @@ -2069,7 +2069,7 @@ ring_is_full: po->stats.stats1.tp_drops++; spin_unlock(&sk->sk_receive_queue.lock); - sk->sk_data_ready(sk, 0); + sk->sk_data_ready(sk); kfree_skb(copy_skb); goto drop_n_restore; } -- cgit v1.2.3-58-ga151