I'd like to propose 34e02c05bb1e (cpuidle: Check the result of cpuidle_get_driver() against NULL) for backporting to -stable. This is a small, non-invasive patch readily reviewed by inspection which fixes a crash if there's no cpuidle driver. We've run into the issue it fixes when testing on stable kernels and though we did use some out of tree patches which made it much easier to trigger the issue is present in the underlying kernel.
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