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/drivers/scsi/iscsi_tcp.c b/drivers/scsi/iscsi_tcp.c
index bfb6d07..1185484 100644
--- a/drivers/scsi/iscsi_tcp.c
+++ b/drivers/scsi/iscsi_tcp.c
@@ -125,7 +125,7 @@ static inline int iscsi_sw_sk_state_check(struct sock *sk)
 	return 0;
 }
 
-static void iscsi_sw_tcp_data_ready(struct sock *sk, int flag)
+static void iscsi_sw_tcp_data_ready(struct sock *sk)
 {
 	struct iscsi_conn *conn;
 	struct iscsi_tcp_conn *tcp_conn;
diff --git a/drivers/scsi/iscsi_tcp.h b/drivers/scsi/iscsi_tcp.h
index 666fe09..f42ecb23 100644
--- a/drivers/scsi/iscsi_tcp.h
+++ b/drivers/scsi/iscsi_tcp.h
@@ -40,7 +40,7 @@ struct iscsi_sw_tcp_conn {
 
 	struct iscsi_sw_tcp_send out;
 	/* old values for socket callbacks */
-	void			(*old_data_ready)(struct sock *, int);
+	void			(*old_data_ready)(struct sock *);
 	void			(*old_state_change)(struct sock *);
 	void			(*old_write_space)(struct sock *);