From: Dan Williams <dan.j.williams@xxxxxxxxx>
Subject: 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@xxxxxxxxx: v2]
Link: http://lkml.kernel.org/r/148728203365.38457.17804568297887708345.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/148693885680.16345.17802627926777862337.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: f931ab479dd2 ("mm: fix devm_memremap_pages crash, use mem_hotplug_{begin, done}")
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Reported-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Toshi Kani <toshi.kani@xxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Logan Gunthorpe <logang@xxxxxxxxxxxx>
Cc: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/memremap.c | 6 ++++++
1 file changed, 6 insertions(+)
diff -puN kernel/memremap.c~mm-devm_memremap_pages-hold-device_hotplug-lock-over-mem_hotplug_begin-done kernel/memremap.c
--- a/kernel/memremap.c~mm-devm_memremap_pages-hold-device_hotplug-lock-over-mem_hotplug_begin-done
+++ a/kernel/memremap.c
@@ -246,9 +246,13 @@ static void devm_memremap_pages_release(
/* 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
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;
_