kasan: disable memory hotplug

Currently memory hotplug won't work with KASan.  As we don't have shadow
for hotplugged memory, kernel will crash on the first access to it.  To
make this work we will need to allocate shadow for new memory.

At some future point proper memory hotplug support will be implemented.
Until then, print a warning at startup and disable memory hot-add.

Signed-off-by: Andrey Ryabinin <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Konstantin Serebryany <[email protected]>
Cc: Dmitry Chernenkov <[email protected]>
Signed-off-by: Andrey Konovalov <[email protected]>
Cc: Yuri Gribov <[email protected]>
Cc: Konstantin Khlebnikov <[email protected]>
Cc: Sasha Levin <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: David Rientjes <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/kasan/kasan.c

@@ -20,6 +20,7 @@
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/memblock.h>
+#include <linux/memory.h>
 #include <linux/mm.h>
 #include <linux/printk.h>
 #include <linux/sched.h>
@@ -300,3 +301,23 @@ EXPORT_SYMBOL(__asan_storeN_noabort);
 /* to shut up compiler complaints */
 void __asan_handle_no_return(void) {}
 EXPORT_SYMBOL(__asan_handle_no_return);
+
+#ifdef CONFIG_MEMORY_HOTPLUG
+static int kasan_mem_notifier(struct notifier_block *nb,
+			unsigned long action, void *data)
+{
+	return (action == MEM_GOING_ONLINE) ? NOTIFY_BAD : NOTIFY_OK;
+}
+
+static int __init kasan_memhotplug_init(void)
+{
+	pr_err("WARNING: KASan doesn't support memory hot-add\n");
+	pr_err("Memory hot-add will be disabled\n");
+
+	hotplug_memory_notifier(kasan_mem_notifier, 0);
+
+	return 0;
+}
+
+module_init(kasan_memhotplug_init);
+#endif