ipv6: check raw payload size correctly in ioctl

[ 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@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 1 insertions, 2 deletions

diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c
index 869ffc76befa..ced3817539c2 100644
--- a/net/ipv6/raw.c
+++ b/net/ipv6/raw.c
@@ -1171,8 +1171,7 @@ static int rawv6_ioctl(struct sock *sk, int cmd, unsigned long arg)
                 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);
         }