Commit 1f7c70d6 authored Oct 21, 2017 by Thomas Gleixner

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: 96abb968 ("smp/hotplug: Allow external multi-instance rollback")
Reported-by: Tvrtko Ursulin <tursulin@ursulin.net>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1710211606130.3213@nanos

parent 33d930e5

kernel/cpu.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -632,6 +632,11 @@ cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup,
		__cpuhp_kick_ap(st);
		}

		/*
		* Clean up the leftovers so the next hotplug operation wont use stale
		* data.
		*/
		st->node = st->last = NULL;
		return ret;
		}

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