Patch "powerpc/sysfs: Fix reference leak of cpu device_nodes present at boot" has been added to the 4.11-stable tree

This is a note to let you know that I've just added the patch titled

powerpc/sysfs: Fix reference leak of cpu device_nodes present at boot

to the 4.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
powerpc-sysfs-fix-reference-leak-of-cpu-device_nodes-present-at-boot.patch
and it can be found in the queue-4.11 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Tyrel Datwyler <[email protected]>
Date: Mon, 17 Apr 2017 20:24:39 -0400
Subject: powerpc/sysfs: Fix reference leak of cpu device_nodes present at boot

From: Tyrel Datwyler <[email protected]>

commit e76ca27790a514590af782f83f6eae49e0ccf8c9 upstream.

For CPUs present at boot each logical CPU acquires a reference to the associated device node of the core. This happens in register_cpu() which is called by topology_init(). The result of this is that we end up with a reference held by each thread of the core. However, these references are never freed if the CPU core is DLPAR removed.

This patch fixes the reference leaks by acquiring and releasing the references in the CPU hotplug callbacks un/register_cpu_online(). With this patch symmetric reference counting is observed with both CPUs present at boot, and those DLPAR added after boot.

---
 arch/powerpc/kernel/sysfs.c |    6 ++++++
 1 file changed, 6 insertions(+)

@@ -710,6 +710,10 @@ static int register_cpu_online(unsigned
 	struct device_attribute *attrs, *pmc_attrs;
 	int i, nattrs;
 
+	/* For cpus present at boot a reference was already grabbed in register_cpu() */
+	if (!s->of_node)
+		s->of_node = of_get_cpu_node(cpu, NULL);
+
 #ifdef CONFIG_PPC64
 	if (cpu_has_feature(CPU_FTR_SMT))
 		device_create_file(s, &dev_attr_smt_snooze_delay);

@@ -864,6 +868,8 @@ static int unregister_cpu_online(unsigne
 	}
 #endif
 	cacheinfo_cpu_offline(cpu);
+	of_node_put(s->of_node);
+	s->of_node = NULL;
 #endif /* CONFIG_HOTPLUG_CPU */
 	return 0;
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.11/powerpc-sysfs-fix-reference-leak-of-cpu-device_nodes-present-at-boot.patch queue-4.11/of-fix-cpus-reference-leak-in-of_numa_parse_cpu_nodes.patch queue-4.11/powerpc-pseries-fix-of_node_put-underflow-during-dlpar-remove.patch