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 <davem@davemloft.net>

1 files changed, 5 insertions, 5 deletions

diff --git a/net/atm/lec.c b/net/atm/lec.c
index 5a2f602d07e1..4c5b8ba0f84f 100644
--- a/net/atm/lec.c
+++ b/net/atm/lec.c
@@ -152,7 +152,7 @@ static void lec_handle_bridge(struct sk_buff *skb, struct net_device *dev)
 		atm_force_charge(priv->lecd, skb2->truesize);
 		sk = sk_atm(priv->lecd);
 		skb_queue_tail(&sk->sk_receive_queue, skb2);
-		sk->sk_data_ready(sk, skb2->len);
+		sk->sk_data_ready(sk);
 	}
 }
 #endif /* defined(CONFIG_BRIDGE) || defined(CONFIG_BRIDGE_MODULE) */
@@ -447,7 +447,7 @@ static int lec_atm_send(struct atm_vcc *vcc, struct sk_buff *skb)
 			atm_force_charge(priv->lecd, skb2->truesize);
 			sk = sk_atm(priv->lecd);
 			skb_queue_tail(&sk->sk_receive_queue, skb2);
-			sk->sk_data_ready(sk, skb2->len);
+			sk->sk_data_ready(sk);
 		}
 	}
 #endif /* defined(CONFIG_BRIDGE) || defined(CONFIG_BRIDGE_MODULE) */
@@ -530,13 +530,13 @@ send_to_lecd(struct lec_priv *priv, atmlec_msg_type type,
 	atm_force_charge(priv->lecd, skb->truesize);
 	sk = sk_atm(priv->lecd);
 	skb_queue_tail(&sk->sk_receive_queue, skb);
-	sk->sk_data_ready(sk, skb->len);
+	sk->sk_data_ready(sk);
 
 	if (data != NULL) {
 		pr_debug("about to send %d bytes of data\n", data->len);
 		atm_force_charge(priv->lecd, data->truesize);
 		skb_queue_tail(&sk->sk_receive_queue, data);
-		sk->sk_data_ready(sk, skb->len);
+		sk->sk_data_ready(sk);
 	}
 
 	return 0;
@@ -616,7 +616,7 @@ static void lec_push(struct atm_vcc *vcc, struct sk_buff *skb)
 
 		pr_debug("%s: To daemon\n", dev->name);
 		skb_queue_tail(&sk->sk_receive_queue, skb);
-		sk->sk_data_ready(sk, skb->len);
+		sk->sk_data_ready(sk);
 	} else {		/* Data frame, queue to protocol handlers */
 		struct lec_arp_table *entry;
 		unsigned char *src, *dst;