cpu/hotplug: Reset node state after operation
The recent rework of the cpu hotplug internals changed the usage of the per
cpu state->node field, but missed to clean it up after usage.
So subsequent hotplug operations use the stale pointer from a previous
operation and hand it into the callback functions. The callbacks then
dereference a pointer which either belongs to a different facility or
points to freed and potentially reused memory. In either case data
corruption and crashes are the obvious consequence.
Reset the node and the last pointers in the per cpu state to NULL after the
operation which set them has completed.
Fixes: 96abb968549c ("smp/hotplug: Allow external multi-instance rollback")
Reported-by: Tvrtko Ursulin <tursulin at ursulin.net>
Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy at linutronix.de>
Cc: Boris Ostrovsky <boris.ostrovsky at oracle.com>
Cc: "Paul E. McKenney" <paulmck at linux.vnet.ibm.com>
Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1710211606130.3213@nanos
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