The mem_hotplug_{begin,done} lock coordinates with
{get,put}_online_mems() to hold off "readers" of the current state of
memory from new hotplug actions. mem_hotplug_begin() expects exclusive
access, via the device_hotplug lock, to set mem_hotplug.active_writer.
Calling mem_hotplug_begin() without locking device_hotplug can lead to
corrupting mem_hotplug.refcount and missed wakeups / soft lockups.Cc: <[email protected]> Cc: Michal Hocko <[email protected]> Cc: Toshi Kani <[email protected]> Cc: Vlastimil Babka <[email protected]> Cc: Logan Gunthorpe <[email protected]> Fixes: f931ab479dd2 ("mm: fix devm_memremap_pages crash, use mem_hotplug_{begin, done}") Reported-by: Ben Hutchings <[email protected]> Signed-off-by: Dan Williams <[email protected]> --- kernel/memremap.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/kernel/memremap.c b/kernel/memremap.c index e6476a8e8b6a..16640415c150 100644 --- a/kernel/memremap.c +++ b/kernel/memremap.c @@ -264,9 +264,12 @@ static void devm_memremap_pages_release(struct device *dev, void *data) } /* pages are dead and unused, undo the arch mapping */ + lock_device_hotplug(); mem_hotplug_begin(); arch_remove_memory(res->start, resource_size(res)); mem_hotplug_done(); + unlock_device_hotplug(); + untrack_pfn(NULL, PHYS_PFN(res->start), resource_size(res)); pgmap_radix_release(res); dev_WARN_ONCE(dev, pgmap->altmap && pgmap->altmap->alloc, @@ -374,9 +377,11 @@ void *devm_memremap_pages(struct device *dev, struct resource *res, if (error) goto err_pfn_remap; + lock_device_hotplug(); mem_hotplug_begin(); error = arch_add_memory(nid, res->start, resource_size(res), true); mem_hotplug_done(); + unlock_device_hotplug(); if (error) goto err_add_memory;
