MFC r302213:

MFC r302213:

Fix a bug introduced in r283433.

[1] Remove unneeded sockaddr conversion before kern_recvit() call as the from
argument is used to record result (the source address of the received message) only.

[2] In Linux the type of msg_namelen member of struct msghdr is signed but native
msg_namelen has a unsigned type (socklen_t). So use the proper storage to fetch fromlen
from userspace and than check the user supplied value and return EINVAL if it is less
than 0 as a Linux do.

Reported by:	Thomas Mueller <tmueller at sysgo dot com> [1]
Tested by:	Thomas Mueller <tmueller at sysgo dot com> [both]
Reviewed by:	kib@

git-svn-id: svn://svn.freebsd.org/base/stable/10@302259 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f