[PATCH v4 1/3] lkdtm/heap: Add vmalloc linear overflow test

[Kees Cook <keescook@xxxxxxxxxxxx>]

Similar to the existing slab overflow and stack exhaustion tests, add
VMALLOC_LINEAR_OVERFLOW (and rename the slab test SLAB_LINEAR_OVERFLOW).

Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
 drivers/misc/lkdtm/core.c               |  3 ++-
 drivers/misc/lkdtm/heap.c               | 21 ++++++++++++++++++++-
 drivers/misc/lkdtm/lkdtm.h              |  3 ++-
 tools/testing/selftests/lkdtm/tests.txt |  3 ++-
 4 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
index b2aff4d87c01..c3a5ad21b3d2 100644
--- a/drivers/misc/lkdtm/core.c
+++ b/drivers/misc/lkdtm/core.c
@@ -119,7 +119,8 @@ static const struct crashtype crashtypes[] = {
 	CRASHTYPE(UNALIGNED_LOAD_STORE_WRITE),
 	CRASHTYPE(FORTIFY_OBJECT),
 	CRASHTYPE(FORTIFY_SUBOBJECT),
-	CRASHTYPE(OVERWRITE_ALLOCATION),
+	CRASHTYPE(SLAB_LINEAR_OVERFLOW),
+	CRASHTYPE(VMALLOC_LINEAR_OVERFLOW),
 	CRASHTYPE(WRITE_AFTER_FREE),
 	CRASHTYPE(READ_AFTER_FREE),
 	CRASHTYPE(WRITE_BUDDY_AFTER_FREE),
diff --git a/drivers/misc/lkdtm/heap.c b/drivers/misc/lkdtm/heap.c
index 1323bc16f113..5d491c22e09a 100644
--- a/drivers/misc/lkdtm/heap.c
+++ b/drivers/misc/lkdtm/heap.c
@@ -5,18 +5,37 @@
  */
 #include "lkdtm.h"
 #include <linux/slab.h>
+#include <linux/vmalloc.h>
 #include <linux/sched.h>
 
 static struct kmem_cache *double_free_cache;
 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);
diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h
index 5ae48c64df24..5a852d0beee0 100644
--- a/drivers/misc/lkdtm/lkdtm.h
+++ b/drivers/misc/lkdtm/lkdtm.h
@@ -38,7 +38,8 @@ void lkdtm_FORTIFY_SUBOBJECT(void);
 /* heap.c */
 void __init lkdtm_heap_init(void);
 void __exit lkdtm_heap_exit(void);
-void lkdtm_OVERWRITE_ALLOCATION(void);
+void lkdtm_VMALLOC_LINEAR_OVERFLOW(void);
+void lkdtm_SLAB_LINEAR_OVERFLOW(void);
 void lkdtm_WRITE_AFTER_FREE(void);
 void lkdtm_READ_AFTER_FREE(void);
 void lkdtm_WRITE_BUDDY_AFTER_FREE(void);
diff --git a/tools/testing/selftests/lkdtm/tests.txt b/tools/testing/selftests/lkdtm/tests.txt
index 11ef159be0fd..322a1d2439e3 100644
--- a/tools/testing/selftests/lkdtm/tests.txt
+++ b/tools/testing/selftests/lkdtm/tests.txt
@@ -15,7 +15,8 @@ UNSET_SMEP CR4 bits went missing
 DOUBLE_FAULT
 CORRUPT_PAC
 UNALIGNED_LOAD_STORE_WRITE
-#OVERWRITE_ALLOCATION Corrupts memory on failure
+VMALLOC_LINEAR_OVERFLOW
+SLAB_LINEAR_OVERFLOW
 #WRITE_AFTER_FREE Corrupts memory on failure
 READ_AFTER_FREE
 #WRITE_BUDDY_AFTER_FREE Corrupts memory on failure
-- 
2.25.1