ethtool: Fix potential kernel buffer overflow in ETHTOOL_GRXCLSRLALL

ethtool: Fix potential kernel buffer overflow in ETHTOOL_GRXCLSRLALL

commit db048b69037e7fa6a7d9e95a1271a50dc08ae233 upstream.

On a 32-bit machine, info.rule_cnt >= 0x40000000 leads to integer
overflow and the buffer may be smaller than needed.  Since
ETHTOOL_GRXCLSRLALL is unprivileged, this can presumably be used for at
least denial of service.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>