ifr name is assumed to be a valid string by the kernel, but nothing
was forcing username to pass a valid string.

In turn, this would cause panics as we tried to access the string
past it's valid memory.
Signed-off-by: NSasha Levin <alexander.levin@verizon.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>