[patch 2/2] mm, hotplug: protect zonelist building withzonelists_mutex

[David Rientjes]

959ecc48fc75 ("mm/memory_hotplug.c: fix building of node hotplug 
zonelist") does not protect the build_all_zonelists() call with 
zonelists_mutex as needed.  This can lead to races in constructing 
zonelist ordering if a concurrent build is underway.  Protecting this with 
lock_memory_hotplug() is insufficient since zonelists can be rebuild 
though sysfs as well.

Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
---
 mm/memory_hotplug.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -498,7 +498,9 @@ static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
 	 * The node we allocated has no zone fallback lists. For avoiding
 	 * to access not-initialized zonelist, build here.
 	 */
+	mutex_lock(&zonelists_mutex);
 	build_all_zonelists(NULL);
+	mutex_unlock(&zonelists_mutex);
 
 	return pgdat;
 }
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