When you are running a Core i7 CPU air cooled at 4.2 GHz with an ambient temperature of 31C, it's not too surprising that your core temperature is up into the 90C range when fully loaded, hopefully with LinX.

Is that a big number? Yes it is.

Is that a bad number? I don't think so. If Intel thought this was a dangerous number then they would lower the thermal throttling point of these chips and your CPU would start to slow down but that usually doesn't happen until a core temperature of 99C or 100C. You are still running your chip within spec at this temperature. Of course the MHz are a little beyond the original design spec but Intel put an adjustable multiplier in these expensive chips for a reason; so the end user could do some easy overclocking without having to think too much. Just increase the multi and away you go.

If you don't run LinX 24/7 then you'll probably be just fine as is. If you do run LinX 24/7 and it goes ka-boom, no worries. Intel puts a 3 year warranty on these things because they know how reliable they are, even at some extreme looking temperatures.

As long as your computer is stable and not thermal throttling then I don't think there's any reason to worry about the core temperature. All Intel Core CPUs are well designed to look after themselves.