lkdtm/heap: Add vmalloc linear overflow test

Similar to the existing slab overflow and stack exhaustion tests, add
VMALLOC_LINEAR_OVERFLOW (and rename the slab test SLAB_LINEAR_OVERFLOW).
Additionally unmarks the test as destructive. (It should be safe in the
face of misbehavior.)

Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210623203936.3151093-6-keescook@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 21 insertions, 1 deletions

diff --git a/drivers/misc/lkdtm/heap.c b/drivers/misc/lkdtm/heap.c
index 1323bc16f113..36be5e353cd0 100644
--- a/drivers/misc/lkdtm/heap.c
+++ b/drivers/misc/lkdtm/heap.c
@@ -5,6 +5,7 @@
  */
 #include "lkdtm.h"
 #include <linux/slab.h>
+#include <linux/vmalloc.h>
 #include <linux/sched.h>
 
 static struct kmem_cache *double_free_cache;
@@ -12,17 +13,36 @@ static struct kmem_cache *a_cache;
 static struct kmem_cache *b_cache;
 
 /*
+ * If there aren't guard pages, it's likely that a consecutive allocation will
+ * let us overflow into the second allocation without overwriting something real.
+ */
+void lkdtm_VMALLOC_LINEAR_OVERFLOW(void)
+{
+	char *one, *two;
+
+	one = vzalloc(PAGE_SIZE);
+	two = vzalloc(PAGE_SIZE);
+
+	pr_info("Attempting vmalloc linear overflow ...\n");
+	memset(one, 0xAA, PAGE_SIZE + 1);
+
+	vfree(two);
+	vfree(one);
+}
+
+/*
  * This tries to stay within the next largest power-of-2 kmalloc cache
  * to avoid actually overwriting anything important if it's not detected
  * correctly.
  */
-void lkdtm_OVERWRITE_ALLOCATION(void)
+void lkdtm_SLAB_LINEAR_OVERFLOW(void)
 {
 	size_t len = 1020;
 	u32 *data = kmalloc(len, GFP_KERNEL);
 	if (!data)
 		return;
 
+	pr_info("Attempting slab linear overflow ...\n");
 	data[1024 / sizeof(u32)] = 0x12345678;
 	kfree(data);
 }