mm, devm_memremap_pages: hold device_hotplug lock over mem_hotplug_{begin, done}

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.

[dan.j.williams@intel.com: v2]
  Link: http://lkml.kernel.org/r/148728203365.38457.17804568297887708345.stgit@dwillia2-desk3.amr.corp.intel.com
Link: http://lkml.kernel.org/r/148693885680.16345.17802627926777862337.stgit@dwillia2-desk3.amr.corp.intel.com
Fixes: f931ab479dd2 ("mm: fix devm_memremap_pages crash, use mem_hotplug_{begin, done}")
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reported-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/kernel/memremap.c b/kernel/memremap.c
index 9ecedc28b928..06123234f118 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -246,9 +246,13 @@ static void devm_memremap_pages_release(struct device *dev, void *data)
         /* pages are dead and unused, undo the arch mapping */
         align_start = res->start & ~(SECTION_SIZE - 1);
         align_size = ALIGN(resource_size(res), SECTION_SIZE);
+
+        lock_device_hotplug();
         mem_hotplug_begin();
         arch_remove_memory(align_start, align_size);
         mem_hotplug_done();
+        unlock_device_hotplug();
+
         untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
         pgmap_radix_release(res);
         dev_WARN_ONCE(dev, pgmap->altmap && pgmap->altmap->alloc,
@@ -360,9 +364,11 @@ 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, align_start, align_size, true);
         mem_hotplug_done();
+        unlock_device_hotplug();
         if (error)
                 goto err_add_memory;