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, 4 insertions, 4 deletions

diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 966763d735e9..96458d434324 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -254,7 +254,7 @@ struct sock_xprt {
         /*
          * Saved socket callback addresses
          */
-        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 *);
         void                    (*old_error_report)(struct sock *);
@@ -946,7 +946,7 @@ static int xs_local_copy_to_xdr(struct xdr_buf *xdr, struct sk_buff *skb)
  *
  * Currently this assumes we can read the whole reply in a single gulp.
  */
-static void xs_local_data_ready(struct sock *sk, int len)
+static void xs_local_data_ready(struct sock *sk)
 {
         struct rpc_task *task;
         struct rpc_xprt *xprt;
@@ -1009,7 +1009,7 @@ static void xs_local_data_ready(struct sock *sk, int len)
  * @len: how much data to read
  *
  */
-static void xs_udp_data_ready(struct sock *sk, int len)
+static void xs_udp_data_ready(struct sock *sk)
 {
         struct rpc_task *task;
         struct rpc_xprt *xprt;
@@ -1432,7 +1432,7 @@ static int xs_tcp_data_recv(read_descriptor_t *rd_desc, struct sk_buff *skb, uns
  * @bytes: how much data to read
  *
  */
-static void xs_tcp_data_ready(struct sock *sk, int bytes)
+static void xs_tcp_data_ready(struct sock *sk)
 {
         struct rpc_xprt *xprt;
         read_descriptor_t rd_desc;