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, 4 insertions, 4 deletions

diff --git a/fs/ncpfs/ncp_fs_sb.h b/fs/ncpfs/ncp_fs_sb.h
index b81e97a..fbb0881 100644
--- a/fs/ncpfs/ncp_fs_sb.h
+++ b/fs/ncpfs/ncp_fs_sb.h
@@ -111,7 +111,7 @@ struct ncp_server {
 
 	spinlock_t requests_lock;	/* Lock accesses to tx.requests, tx.creq and rcv.creq when STREAM mode */
 
-	void (*data_ready)(struct sock* sk, int len);
+	void (*data_ready)(struct sock* sk);
 	void (*error_report)(struct sock* sk);
 	void (*write_space)(struct sock* sk);	/* STREAM mode only */
 	struct {
@@ -153,7 +153,7 @@ extern void ncp_tcp_tx_proc(struct work_struct *work);
 extern void ncpdgram_rcv_proc(struct work_struct *work);
 extern void ncpdgram_timeout_proc(struct work_struct *work);
 extern void ncpdgram_timeout_call(unsigned long server);
-extern void ncp_tcp_data_ready(struct sock* sk, int len);
+extern void ncp_tcp_data_ready(struct sock* sk);
 extern void ncp_tcp_write_space(struct sock* sk);
 extern void ncp_tcp_error_report(struct sock* sk);
 
diff --git a/fs/ncpfs/sock.c b/fs/ncpfs/sock.c
index 3a15872..652da0d 100644
--- a/fs/ncpfs/sock.c
+++ b/fs/ncpfs/sock.c
@@ -96,11 +96,11 @@ static void ncp_req_put(struct ncp_request_reply *req)
 		kfree(req);
 }
 
-void ncp_tcp_data_ready(struct sock *sk, int len)
+void ncp_tcp_data_ready(struct sock *sk)
 {
 	struct ncp_server *server = sk->sk_user_data;
 
-	server->data_ready(sk, len);
+	server->data_ready(sk);
 	schedule_work(&server->rcv.tq);
 }