Running a mainline kernel on a cellphone

There are all kinds of kernel bugs in every android release. That's just a simple fact. Most of root exploits are actually exploits of either the kernel or a privileged service running on top of it. We wouldn't be able to attain root without it.

Though better security would be a nice thing I doubt we'll see it unless the ARM phone chip guys embrace openness. Qualacom and others are openly hostile to openness.