2 files changed, 35 insertions, 6 deletions

diff --git a/mm/Kconfig b/mm/Kconfig
index 46ef77d5c332..48b1af447fa7 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -161,7 +161,6 @@ config MEMORY_HOTPLUG
         bool "Allow for memory hot-add"
         depends on SPARSEMEM || X86_64_ACPI_NUMA
         depends on ARCH_ENABLE_MEMORY_HOTPLUG
-        depends on COMPILE_TEST || !KASAN
 
 config MEMORY_HOTPLUG_SPARSE
         def_bool y
diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index 212bc62041de..509974a1911e 100644
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -737,17 +737,47 @@ void __asan_unpoison_stack_memory(const void *addr, size_t size)
 EXPORT_SYMBOL(__asan_unpoison_stack_memory);
 
 #ifdef CONFIG_MEMORY_HOTPLUG
-static int kasan_mem_notifier(struct notifier_block *nb,
+static int __meminit kasan_mem_notifier(struct notifier_block *nb,
                         unsigned long action, void *data)
 {
-        return (action == MEM_GOING_ONLINE) ? NOTIFY_BAD : NOTIFY_OK;
+        struct memory_notify *mem_data = data;
+        unsigned long nr_shadow_pages, start_kaddr, shadow_start;
+        unsigned long shadow_end, shadow_size;
+
+        nr_shadow_pages = mem_data->nr_pages >> KASAN_SHADOW_SCALE_SHIFT;
+        start_kaddr = (unsigned long)pfn_to_kaddr(mem_data->start_pfn);
+        shadow_start = (unsigned long)kasan_mem_to_shadow((void *)start_kaddr);
+        shadow_size = nr_shadow_pages << PAGE_SHIFT;
+        shadow_end = shadow_start + shadow_size;
+
+        if (WARN_ON(mem_data->nr_pages % KASAN_SHADOW_SCALE_SIZE) ||
+                WARN_ON(start_kaddr % (KASAN_SHADOW_SCALE_SIZE << PAGE_SHIFT)))
+                return NOTIFY_BAD;
+
+        switch (action) {
+        case MEM_GOING_ONLINE: {
+                void *ret;
+
+                ret = __vmalloc_node_range(shadow_size, PAGE_SIZE, shadow_start,
+                                        shadow_end, GFP_KERNEL,
+                                        PAGE_KERNEL, VM_NO_GUARD,
+                                        pfn_to_nid(mem_data->start_pfn),
+                                        __builtin_return_address(0));
+                if (!ret)
+                        return NOTIFY_BAD;
+
+                kmemleak_ignore(ret);
+                return NOTIFY_OK;
+        }
+        case MEM_OFFLINE:
+                vfree((void *)shadow_start);
+        }
+
+        return NOTIFY_OK;
 }
 
 static int __init kasan_memhotplug_init(void)
 {
-        pr_info("WARNING: KASAN doesn't support memory hot-add\n");
-        pr_info("Memory hot-add will be disabled\n");
-
         hotplug_memory_notifier(kasan_mem_notifier, 0);
 
         return 0;