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>

1 files changed, 146 insertions, 0 deletions

diff --git a/drivers/misc/lkdtm_heap.c b/drivers/misc/lkdtm_heap.c
new file mode 100644
index 000000000000..12f50e8dcbfe
--- /dev/null
+++ b/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);
+}