[PATCH 4.10 43/62] ipv6: check raw payload size correctly in ioctl

[Greg Kroah-Hartman]

4.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jamie Bainbridge <jbainbri@xxxxxxxxxx>


[ Upstream commit 105f5528b9bbaa08b526d3405a5bcd2ff0c953c8 ]

In situations where an skb is paged, the transport header pointer and
tail pointer can be the same because the skb contents are in frags.

This results in ioctl(SIOCINQ/FIONREAD) incorrectly returning a
length of 0 when the length to receive is actually greater than zero.

skb->len is already correctly set in ip6_input_finish() with
pskb_pull(), so use skb->len as it always returns the correct result
for both linear and paged data.

Signed-off-by: Jamie Bainbridge <jbainbri@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/ipv6/raw.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/net/ipv6/raw.c
+++ b/net/ipv6/raw.c
@@ -1174,8 +1174,7 @@ static int rawv6_ioctl(struct sock *sk,
 		spin_lock_bh(&sk->sk_receive_queue.lock);
 		skb = skb_peek(&sk->sk_receive_queue);
 		if (skb)
-			amount = skb_tail_pointer(skb) -
-				skb_transport_header(skb);
+			amount = skb->len;
 		spin_unlock_bh(&sk->sk_receive_queue.lock);
 		return put_user(amount, (int __user *)arg);
 	}