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>

2 files changed, 2 insertions, 2 deletions

diff --git a/net/dccp/input.c b/net/dccp/input.c
index 14cdafa..3c8ec7d 100644
--- a/net/dccp/input.c
+++ b/net/dccp/input.c
@@ -28,7 +28,7 @@ static void dccp_enqueue_skb(struct sock *sk, struct sk_buff *skb)
 	__skb_pull(skb, dccp_hdr(skb)->dccph_doff * 4);
 	__skb_queue_tail(&sk->sk_receive_queue, skb);
 	skb_set_owner_r(skb, sk);
-	sk->sk_data_ready(sk, 0);
+	sk->sk_data_ready(sk);
 }
 
 static void dccp_fin(struct sock *sk, struct sk_buff *skb)
diff --git a/net/dccp/minisocks.c b/net/dccp/minisocks.c
index 9e2f78b..c69eb9c 100644
--- a/net/dccp/minisocks.c
+++ b/net/dccp/minisocks.c
@@ -237,7 +237,7 @@ int dccp_child_process(struct sock *parent, struct sock *child,
 
 		/* Wakeup parent, send SIGIO */
 		if (state == DCCP_RESPOND && child->sk_state != state)
-			parent->sk_data_ready(parent, 0);
+			parent->sk_data_ready(parent);
 	} else {
 		/* Alas, it is possible again, because we do lookup
 		 * in main socket hash table and lock on listening