net: sock: validate data_len before allocating skb in sock_alloc_send_pskb()

We need to validate the number of pages consumed by data_len, otherwise frags
array could be overflowed by userspace. So this patch validate data_len and
return -EMSGSIZE when data_len may occupies more frags than MAX_SKB_FRAGS.

Change-Id: I2a7d6bb93e4fa04efc6f576d22277f43b11257d3
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Git-commit: cc9b17ad29ecaa20bfe426a8d4dbfb94b13ff1cc
Git-repo: https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>