mm, kasan: add a ksize() test

Add a test that makes sure ksize() unpoisons the whole chunk.

Signed-off-by: Alexander Potapenko <glider@google.com>
Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Andrey Konovalov <adech.fo@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Konstantin Serebryany <kcc@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/test_kasan.c

@@ -344,6 +344,25 @@ static noinline void __init kasan_stack_oob(void)
 	*(volatile char *)p;
 }
 
+static noinline void __init ksize_unpoisons_memory(void)
+{
+	char *ptr;
+	size_t size = 123, real_size = size;
+
+	pr_info("ksize() unpoisons the whole allocated chunk\n");
+	ptr = kmalloc(size, GFP_KERNEL);
+	if (!ptr) {
+		pr_err("Allocation failed\n");
+		return;
+	}
+	real_size = ksize(ptr);
+	/* This access doesn't trigger an error. */
+	ptr[size] = 'x';
+	/* This one does. */
+	ptr[real_size] = 'y';
+	kfree(ptr);
+}
+
 static int __init kmalloc_tests_init(void)
 {
 	kmalloc_oob_right();
@@ -367,6 +386,7 @@ static int __init kmalloc_tests_init(void)
 	kmem_cache_oob();
 	kasan_stack_oob();
 	kasan_global_oob();
+	ksize_unpoisons_memory();
 	return -EAGAIN;
 }