net: ipv4: fix for a race condition in raw_sendmsg

net: ipv4: fix for a race condition in raw_sendmsg

inet->hdrincl is racy, and could lead to uninitialized stack pointer
usage, so its value should be read only once.

Fixes: c008ba5bdc9f ("ipv4: Avoid reading user iov twice after raw_probe_proto_opt")
Signed-off-by: Mohamed Ghannam <simo.ghannam@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 8f659a03a0ba9289b9aeb9b4470e6fb263d6f483)

Orabug: 27390679
CVE: CVE-2017-17712

Signed-off-by: Tim Tianyang Chen <tianyang.chen@oracle.com>
Reviewed-by: Jack Vogel <jack.vogel@oracle.com>
 Conflicts:
	net/ipv4/raw.c