commit d496f784 upstream.

A ROSE socket doesn't necessarily always have a neighbour pointer so check
if the neighbour pointer is valid before dereferencing it.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Tested-by: Bernard Pidoux <f6bvp@free.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Zefan Li <lizefan@huawei.com>