MFC r309027:

MFC r309027:

Allocate a struct ifreq rather than using a (wrong) computed size for
the BIOCSETIF ioctl.

The kernel always copies an entire struct ifreq and IPv4 addresses will
always fit in an ifreq.

On systems with pointers larger than 64-bits, the computed size will be
less than the size of struct ifreq, potentially resulting in the kernel
attempting to copyin memory from outside the allocation.

Reviewed by:	jhb
Obtained from:	CheriBSD
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D8445

git-svn-id: svn://svn.freebsd.org/base/stable/10@309304 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f