lkdtm: split heap corruption tests to separate file

This splits the *_AFTER_FREE and related tests into the new lkdtm_heap.c
file to help separate things better for readability.

Signed-off-by: Kees Cook <keescook@chromium.org>

drivers/misc/Makefile

@@ -59,6 +59,7 @@ obj-$(CONFIG_CXL_BASE)		+= cxl/
 obj-$(CONFIG_PANEL)             += panel.o
 
 lkdtm-$(CONFIG_LKDTM)		+= lkdtm_core.o
+lkdtm-$(CONFIG_LKDTM)		+= lkdtm_heap.o
 lkdtm-$(CONFIG_LKDTM)		+= lkdtm_perms.o
 lkdtm-$(CONFIG_LKDTM)		+= lkdtm_rodata_objcopy.o
 lkdtm-$(CONFIG_LKDTM)		+= lkdtm_usercopy.o

drivers/misc/lkdtm.h

@@ -1,6 +1,13 @@
 #ifndef __LKDTM_H
 #define __LKDTM_H
 
+/* lkdtm_heap.c */
+void lkdtm_OVERWRITE_ALLOCATION(void);
+void lkdtm_WRITE_AFTER_FREE(void);
+void lkdtm_READ_AFTER_FREE(void);
+void lkdtm_WRITE_BUDDY_AFTER_FREE(void);
+void lkdtm_READ_BUDDY_AFTER_FREE(void);
+
 /* lkdtm_perms.c */
 void __init lkdtm_perms_init(void);
 void lkdtm_WRITE_RO(void);

drivers/misc/lkdtm_core.c

@@ -384,125 +384,21 @@ static void lkdtm_do_action(enum ctype which)
 		*p = val;
 		 break;
 	}
-	case CT_OVERWRITE_ALLOCATION: {
-		size_t len = 1020;
-		u32 *data = kmalloc(len, GFP_KERNEL);
-
-		data[1024 / sizeof(u32)] = 0x12345678;
-		kfree(data);
+	case CT_OVERWRITE_ALLOCATION:
+		lkdtm_OVERWRITE_ALLOCATION();
 		break;
-	}
-	case CT_WRITE_AFTER_FREE: {
-		int *base, *again;
-		size_t len = 1024;
-		/*
-		 * The slub allocator uses the first word to store the free
-		 * pointer in some configurations. Use the middle of the
-		 * allocation to avoid running into the freelist
-		 */
-		size_t offset = (len / sizeof(*base)) / 2;
-
-		base = kmalloc(len, GFP_KERNEL);
-		pr_info("Allocated memory %p-%p\n", base, &base[offset * 2]);
-		pr_info("Attempting bad write to freed memory at %p\n",
-			&base[offset]);
-		kfree(base);
-		base[offset] = 0x0abcdef0;
-		/* Attempt to notice the overwrite. */
-		again = kmalloc(len, GFP_KERNEL);
-		kfree(again);
-		if (again != base)
-			pr_info("Hmm, didn't get the same memory range.\n");
-
+	case CT_WRITE_AFTER_FREE:
+		lkdtm_WRITE_AFTER_FREE();
 		break;
-	}
-	case CT_READ_AFTER_FREE: {
-		int *base, *val, saw;
-		size_t len = 1024;
-		/*
-		 * The slub allocator uses the first word to store the free
-		 * pointer in some configurations. Use the middle of the
-		 * allocation to avoid running into the freelist
-		 */
-		size_t offset = (len / sizeof(*base)) / 2;
-
-		base = kmalloc(len, GFP_KERNEL);
-		if (!base)
-			break;
-
-		val = kmalloc(len, GFP_KERNEL);
-		if (!val) {
-			kfree(base);
-			break;
-		}
-
-		*val = 0x12345678;
-		base[offset] = *val;
-		pr_info("Value in memory before free: %x\n", base[offset]);
-
-		kfree(base);
-
-		pr_info("Attempting bad read from freed memory\n");
-		saw = base[offset];
-		if (saw != *val) {
-			/* Good! Poisoning happened, so declare a win. */
-			pr_info("Memory correctly poisoned (%x)\n", saw);
-			BUG();
-		}
-		pr_info("Memory was not poisoned\n");
-
-		kfree(val);
+	case CT_READ_AFTER_FREE:
+		lkdtm_READ_AFTER_FREE();
 		break;
-	}
-	case CT_WRITE_BUDDY_AFTER_FREE: {
-		unsigned long p = __get_free_page(GFP_KERNEL);
-		if (!p)
-			break;
-		pr_info("Writing to the buddy page before free\n");
-		memset((void *)p, 0x3, PAGE_SIZE);
-		free_page(p);
-		schedule();
-		pr_info("Attempting bad write to the buddy page after free\n");
-		memset((void *)p, 0x78, PAGE_SIZE);
-		/* Attempt to notice the overwrite. */
-		p = __get_free_page(GFP_KERNEL);
-		free_page(p);
-		schedule();
-
+	case CT_WRITE_BUDDY_AFTER_FREE:
+		lkdtm_WRITE_BUDDY_AFTER_FREE();
 		break;
-	}
-	case CT_READ_BUDDY_AFTER_FREE: {
-		unsigned long p = __get_free_page(GFP_KERNEL);
-		int saw, *val;
-		int *base;
-
-		if (!p)
-			break;
-
-		val = kmalloc(1024, GFP_KERNEL);
-		if (!val) {
-			free_page(p);
-			break;
-		}
-
-		base = (int *)p;
-
-		*val = 0x12345678;
-		base[0] = *val;
-		pr_info("Value in memory before free: %x\n", base[0]);
-		free_page(p);
-		pr_info("Attempting to read from freed memory\n");
-		saw = base[0];
-		if (saw != *val) {
-			/* Good! Poisoning happened, so declare a win. */
-			pr_info("Memory correctly poisoned (%x)\n", saw);
-			BUG();
-		}
-		pr_info("Buddy page was not poisoned\n");
-
-		kfree(val);
+	case CT_READ_BUDDY_AFTER_FREE:
+		lkdtm_READ_BUDDY_AFTER_FREE();
 		break;
-	}
 	case CT_SOFTLOCKUP:
 		preempt_disable();
 		for (;;)

drivers/misc/lkdtm_heap.c

@@ -0,0 +1,146 @@
+/*
+ * This is for all the tests relating directly to heap memory, including
+ * page allocation and slab allocations.
+ */
+#define pr_fmt(fmt) "lkdtm: " fmt
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+
+#include "lkdtm.h"
+
+/*
+ * 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)
+{
+	size_t len = 1020;
+	u32 *data = kmalloc(len, GFP_KERNEL);
+
+	data[1024 / sizeof(u32)] = 0x12345678;
+	kfree(data);
+}
+
+void lkdtm_WRITE_AFTER_FREE(void)
+{
+	int *base, *again;
+	size_t len = 1024;
+	/*
+	 * The slub allocator uses the first word to store the free
+	 * pointer in some configurations. Use the middle of the
+	 * allocation to avoid running into the freelist
+	 */
+	size_t offset = (len / sizeof(*base)) / 2;
+
+	base = kmalloc(len, GFP_KERNEL);
+	pr_info("Allocated memory %p-%p\n", base, &base[offset * 2]);
+	pr_info("Attempting bad write to freed memory at %p\n",
+		&base[offset]);
+	kfree(base);
+	base[offset] = 0x0abcdef0;
+	/* Attempt to notice the overwrite. */
+	again = kmalloc(len, GFP_KERNEL);
+	kfree(again);
+	if (again != base)
+		pr_info("Hmm, didn't get the same memory range.\n");
+}
+
+void lkdtm_READ_AFTER_FREE(void)
+{
+	int *base, *val, saw;
+	size_t len = 1024;
+	/*
+	 * The slub allocator uses the first word to store the free
+	 * pointer in some configurations. Use the middle of the
+	 * allocation to avoid running into the freelist
+	 */
+	size_t offset = (len / sizeof(*base)) / 2;
+
+	base = kmalloc(len, GFP_KERNEL);
+	if (!base) {
+		pr_info("Unable to allocate base memory.\n");
+		return;
+	}
+
+	val = kmalloc(len, GFP_KERNEL);
+	if (!val) {
+		pr_info("Unable to allocate val memory.\n");
+		kfree(base);
+		return;
+	}
+
+	*val = 0x12345678;
+	base[offset] = *val;
+	pr_info("Value in memory before free: %x\n", base[offset]);
+
+	kfree(base);
+
+	pr_info("Attempting bad read from freed memory\n");
+	saw = base[offset];
+	if (saw != *val) {
+		/* Good! Poisoning happened, so declare a win. */
+		pr_info("Memory correctly poisoned (%x)\n", saw);
+		BUG();
+	}
+	pr_info("Memory was not poisoned\n");
+
+	kfree(val);
+}
+
+void lkdtm_WRITE_BUDDY_AFTER_FREE(void)
+{
+	unsigned long p = __get_free_page(GFP_KERNEL);
+	if (!p) {
+		pr_info("Unable to allocate free page\n");
+		return;
+	}
+
+	pr_info("Writing to the buddy page before free\n");
+	memset((void *)p, 0x3, PAGE_SIZE);
+	free_page(p);
+	schedule();
+	pr_info("Attempting bad write to the buddy page after free\n");
+	memset((void *)p, 0x78, PAGE_SIZE);
+	/* Attempt to notice the overwrite. */
+	p = __get_free_page(GFP_KERNEL);
+	free_page(p);
+	schedule();
+}
+
+void lkdtm_READ_BUDDY_AFTER_FREE(void)
+{
+	unsigned long p = __get_free_page(GFP_KERNEL);
+	int saw, *val;
+	int *base;
+
+	if (!p) {
+		pr_info("Unable to allocate free page\n");
+		return;
+	}
+
+	val = kmalloc(1024, GFP_KERNEL);
+	if (!val) {
+		pr_info("Unable to allocate val memory.\n");
+		free_page(p);
+		return;
+	}
+
+	base = (int *)p;
+
+	*val = 0x12345678;
+	base[0] = *val;
+	pr_info("Value in memory before free: %x\n", base[0]);
+	free_page(p);
+	pr_info("Attempting to read from freed memory\n");
+	saw = base[0];
+	if (saw != *val) {
+		/* Good! Poisoning happened, so declare a win. */
+		pr_info("Memory correctly poisoned (%x)\n", saw);
+		BUG();
+	}
+	pr_info("Buddy page was not poisoned\n");
+
+	kfree(val);
+}