drivers/misc/lkdtm/bugs.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * This is for all the tests related to logic bugs (e.g. bad dereferences,
  * bad alignment, bad loops, bad locking, bad scheduling, deep stacks, and
  * lockups) along with other things that don't fit well into existing LKDTM
  * test source files.
  */
 #include "lkdtm.h"
 #include <linux/list.h>
 #include <linux/sched.h>
 #include <linux/sched/signal.h>
 #include <linux/sched/task_stack.h>
 #include <linux/uaccess.h>
 #include <linux/slab.h>

 #if IS_ENABLED(CONFIG_X86_32) && !IS_ENABLED(CONFIG_UML)
 #include <asm/desc.h>
 #endif

 struct lkdtm_list {
 	struct list_head node;
 };

 /*
  * Make sure our attempts to over run the kernel stack doesn't trigger
  * a compiler warning when CONFIG_FRAME_WARN is set. Then make sure we
  * recurse past the end of THREAD_SIZE by default.
  */
 #if defined(CONFIG_FRAME_WARN) && (CONFIG_FRAME_WARN > 0)
 #define REC_STACK_SIZE (_AC(CONFIG_FRAME_WARN, UL) / 2)
 #else
 #define REC_STACK_SIZE (THREAD_SIZE / 8UL)
 #endif
 #define REC_NUM_DEFAULT ((THREAD_SIZE / REC_STACK_SIZE) * 2)

 static int recur_count = REC_NUM_DEFAULT;

 static DEFINE_SPINLOCK(lock_me_up);

 /*
  * Make sure compiler does not optimize this function or stack frame away:
  * - function marked noinline
  * - stack variables are marked volatile
  * - stack variables are written (memset()) and read (buf[..] passed as arg)
  * - function may have external effects (memzero_explicit())
  * - no tail recursion possible
  */
 static int noinline recursive_loop(int remaining)
 {
 	volatile char buf[REC_STACK_SIZE];
 	volatile int ret;

 	memset((void *)buf, remaining & 0xFF, sizeof(buf));
 	if (!remaining)
 		ret = 0;
 	else
 		ret = recursive_loop((int)buf[remaining % sizeof(buf)] - 1);
 	memzero_explicit((void *)buf, sizeof(buf));
 	return ret;
 }

 /* If the depth is negative, use the default, otherwise keep parameter. */
 void __init lkdtm_bugs_init(int *recur_param)
 {
 	if (*recur_param < 0)
 		*recur_param = recur_count;
 	else
 		recur_count = *recur_param;
 }

 static void lkdtm_PANIC(void)
 {
 	panic("dumptest");
 }

 static void lkdtm_BUG(void)
 {
 	BUG();
 }

 static int warn_counter;

 static void lkdtm_WARNING(void)
 {
 	WARN_ON(++warn_counter);
 }

 static void lkdtm_WARNING_MESSAGE(void)
 {
 	WARN(1, "Warning message trigger count: %d\n", ++warn_counter);
 }

 static void lkdtm_EXCEPTION(void)
 {
 	*((volatile int *) 0) = 0;
 }

 static void lkdtm_LOOP(void)
 {
 	for (;;)
 		;
 }

 static void lkdtm_EXHAUST_STACK(void)
 {
 	pr_info("Calling function with %lu frame size to depth %d ...\n",
 		REC_STACK_SIZE, recur_count);
 	recursive_loop(recur_count);
 	pr_info("FAIL: survived without exhausting stack?!\n");
 }

 static noinline void __lkdtm_CORRUPT_STACK(void *stack)
 {
 	memset(stack, '\xff', 64);
 }

 /* This should trip the stack canary, not corrupt the return address. */
 static noinline void lkdtm_CORRUPT_STACK(void)
 {
 	/* Use default char array length that triggers stack protection. */
 	char data[8] __aligned(sizeof(void *));

 	pr_info("Corrupting stack containing char array ...\n");
 	__lkdtm_CORRUPT_STACK((void *)&data);
 }

 /* Same as above but will only get a canary with -fstack-protector-strong */
 static noinline void lkdtm_CORRUPT_STACK_STRONG(void)
 {
 	union {
 		unsigned short shorts[4];
 		unsigned long *ptr;
 	} data __aligned(sizeof(void *));

 	pr_info("Corrupting stack containing union ...\n");
 	__lkdtm_CORRUPT_STACK((void *)&data);
 }

 static pid_t stack_pid;
 static unsigned long stack_addr;

 static void lkdtm_REPORT_STACK(void)
 {
 	volatile uintptr_t magic;
 	pid_t pid = task_pid_nr(current);

 	if (pid != stack_pid) {
 		pr_info("Starting stack offset tracking for pid %d\n", pid);
 		stack_pid = pid;
 		stack_addr = (uintptr_t)&magic;
 	}

 	pr_info("Stack offset: %d\n", (int)(stack_addr - (uintptr_t)&magic));
 }

 static pid_t stack_canary_pid;
 static unsigned long stack_canary;
 static unsigned long stack_canary_offset;

 static noinline void __lkdtm_REPORT_STACK_CANARY(void *stack)
 {
 	int i = 0;
 	pid_t pid = task_pid_nr(current);
 	unsigned long *canary = (unsigned long *)stack;
 	unsigned long current_offset = 0, init_offset = 0;

 	/* Do our best to find the canary in a 16 word window ... */
 	for (i = 1; i < 16; i++) {
 		canary = (unsigned long *)stack + i;
 #ifdef CONFIG_STACKPROTECTOR
 		if (*canary == current->stack_canary)
 			current_offset = i;
 		if (*canary == init_task.stack_canary)
 			init_offset = i;
 #endif
 	}

 	if (current_offset == 0) {
 		/*
 		 * If the canary doesn't match what's in the task_struct,
 		 * we're either using a global canary or the stack frame
 		 * layout changed.
 		 */
 		if (init_offset != 0) {
 			pr_err("FAIL: global stack canary found at offset %ld (canary for pid %d matches init_task's)!\n",
 			       init_offset, pid);
 		} else {
 			pr_warn("FAIL: did not correctly locate stack canary :(\n");
 			pr_expected_config(CONFIG_STACKPROTECTOR);
 		}

 		return;
 	} else if (init_offset != 0) {
 		pr_warn("WARNING: found both current and init_task canaries nearby?!\n");
 	}

 	canary = (unsigned long *)stack + current_offset;
 	if (stack_canary_pid == 0) {
 		stack_canary = *canary;
 		stack_canary_pid = pid;
 		stack_canary_offset = current_offset;
 		pr_info("Recorded stack canary for pid %d at offset %ld\n",
 			stack_canary_pid, stack_canary_offset);
 	} else if (pid == stack_canary_pid) {
 		pr_warn("ERROR: saw pid %d again -- please use a new pid\n", pid);
 	} else {
 		if (current_offset != stack_canary_offset) {
 			pr_warn("ERROR: canary offset changed from %ld to %ld!?\n",
 				stack_canary_offset, current_offset);
 			return;
 		}

 		if (*canary == stack_canary) {
 			pr_warn("FAIL: canary identical for pid %d and pid %d at offset %ld!\n",
 				stack_canary_pid, pid, current_offset);
 		} else {
 			pr_info("ok: stack canaries differ between pid %d and pid %d at offset %ld.\n",
 				stack_canary_pid, pid, current_offset);
 			/* Reset the test. */
 			stack_canary_pid = 0;
 		}
 	}
 }

 static void lkdtm_REPORT_STACK_CANARY(void)
 {
 	/* Use default char array length that triggers stack protection. */
 	char data[8] __aligned(sizeof(void *)) = { };

 	__lkdtm_REPORT_STACK_CANARY((void *)&data);
 }

 static void lkdtm_UNALIGNED_LOAD_STORE_WRITE(void)
 {
 	static u8 data[5] __attribute__((aligned(4))) = {1, 2, 3, 4, 5};
 	u32 *p;
 	u32 val = 0x12345678;

 	p = (u32 *)(data + 1);
 	if (*p == 0)
 		val = 0x87654321;
 	*p = val;

 	if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
 		pr_err("XFAIL: arch has CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS\n");
 }

 static void lkdtm_SOFTLOCKUP(void)
 {
 	preempt_disable();
 	for (;;)
 		cpu_relax();
 }

 static void lkdtm_HARDLOCKUP(void)
 {
 	local_irq_disable();
 	for (;;)
 		cpu_relax();
 }

 static void lkdtm_SPINLOCKUP(void)
 {
 	/* Must be called twice to trigger. */
 	spin_lock(&lock_me_up);
 	/* Let sparse know we intended to exit holding the lock. */
 	__release(&lock_me_up);
 }

 static void lkdtm_HUNG_TASK(void)
 {
 	set_current_state(TASK_UNINTERRUPTIBLE);
 	schedule();
 }

 static volatile unsigned int huge = INT_MAX - 2;
 static volatile unsigned int ignored;

 static void lkdtm_OVERFLOW_SIGNED(void)
 {
 	int value;

 	value = huge;
 	pr_info("Normal signed addition ...\n");
 	value += 1;
 	ignored = value;

 	pr_info("Overflowing signed addition ...\n");
 	value += 4;
 	ignored = value;
 }


 static void lkdtm_OVERFLOW_UNSIGNED(void)
 {
 	unsigned int value;

 	value = huge;
 	pr_info("Normal unsigned addition ...\n");
 	value += 1;
 	ignored = value;

 	pr_info("Overflowing unsigned addition ...\n");
 	value += 4;
 	ignored = value;
 }

 /* Intentionally using unannotated flex array definition. */
 struct array_bounds_flex_array {
 	int one;
 	int two;
 	char data[];
 };

 struct array_bounds {
 	int one;
 	int two;
 	char data[8];
 	int three;
 };

 static void lkdtm_ARRAY_BOUNDS(void)
 {
 	struct array_bounds_flex_array *not_checked;
 	struct array_bounds *checked;
 	volatile int i;

 	not_checked = kmalloc(sizeof(*not_checked) * 2, GFP_KERNEL);
 	checked = kmalloc(sizeof(*checked) * 2, GFP_KERNEL);
 	if (!not_checked || !checked) {
 		kfree(not_checked);
 		kfree(checked);
 		return;
 	}

 	pr_info("Array access within bounds ...\n");
 	/* For both, touch all bytes in the actual member size. */
 	for (i = 0; i < sizeof(checked->data); i++)
 		checked->data[i] = 'A';
 	/*
 	 * For the uninstrumented flex array member, also touch 1 byte
 	 * beyond to verify it is correctly uninstrumented.
 	 */
 	for (i = 0; i < 2; i++)
 		not_checked->data[i] = 'A';

 	pr_info("Array access beyond bounds ...\n");
 	for (i = 0; i < sizeof(checked->data) + 1; i++)
 		checked->data[i] = 'B';

 	kfree(not_checked);
 	kfree(checked);
 	pr_err("FAIL: survived array bounds overflow!\n");
 	if (IS_ENABLED(CONFIG_UBSAN_BOUNDS))
 		pr_expected_config(CONFIG_UBSAN_TRAP);
 	else
 		pr_expected_config(CONFIG_UBSAN_BOUNDS);
 }

 struct lkdtm_annotated {
 	unsigned long flags;
 	int count;
 	int array[] __counted_by(count);
 };

 static volatile int fam_count = 4;

 static void lkdtm_FAM_BOUNDS(void)
 {
 	struct lkdtm_annotated *inst;

 	inst = kzalloc(struct_size(inst, array, fam_count + 1), GFP_KERNEL);
 	if (!inst) {
 		pr_err("FAIL: could not allocate test struct!\n");
 		return;
 	}

 	inst->count = fam_count;
 	pr_info("Array access within bounds ...\n");
 	inst->array[1] = fam_count;
 	ignored = inst->array[1];

 	pr_info("Array access beyond bounds ...\n");
 	inst->array[fam_count] = fam_count;
 	ignored = inst->array[fam_count];

 	kfree(inst);

 	pr_err("FAIL: survived access of invalid flexible array member index!\n");

 	if (!__has_attribute(__counted_by__))
 		pr_warn("This is expected since this %s was built a compiler supporting __counted_by\n",
 			lkdtm_kernel_info);
 	else if (IS_ENABLED(CONFIG_UBSAN_BOUNDS))
 		pr_expected_config(CONFIG_UBSAN_TRAP);
 	else
 		pr_expected_config(CONFIG_UBSAN_BOUNDS);
 }

 static void lkdtm_CORRUPT_LIST_ADD(void)
 {
 	/*
 	 * Initially, an empty list via LIST_HEAD:
 	 *	test_head.next = &test_head
 	 *	test_head.prev = &test_head
 	 */
 	LIST_HEAD(test_head);
 	struct lkdtm_list good, bad;
 	void *target[2] = { };
 	void *redirection = &target;

 	pr_info("attempting good list addition\n");

 	/*
 	 * Adding to the list performs these actions:
 	 *	test_head.next->prev = &good.node
 	 *	good.node.next = test_head.next
 	 *	good.node.prev = test_head
 	 *	test_head.next = good.node
 	 */
 	list_add(&good.node, &test_head);

 	pr_info("attempting corrupted list addition\n");
 	/*
 	 * In simulating this "write what where" primitive, the "what" is
 	 * the address of &bad.node, and the "where" is the address held
 	 * by "redirection".
 	 */
 	test_head.next = redirection;
 	list_add(&bad.node, &test_head);

 	if (target[0] == NULL && target[1] == NULL)
 		pr_err("Overwrite did not happen, but no BUG?!\n");
 	else {
 		pr_err("list_add() corruption not detected!\n");
 		pr_expected_config(CONFIG_LIST_HARDENED);
 	}
 }

 static void lkdtm_CORRUPT_LIST_DEL(void)
 {
 	LIST_HEAD(test_head);
 	struct lkdtm_list item;
 	void *target[2] = { };
 	void *redirection = &target;

 	list_add(&item.node, &test_head);

 	pr_info("attempting good list removal\n");
 	list_del(&item.node);

 	pr_info("attempting corrupted list removal\n");
 	list_add(&item.node, &test_head);

 	/* As with the list_add() test above, this corrupts "next". */
 	item.node.next = redirection;
 	list_del(&item.node);

 	if (target[0] == NULL && target[1] == NULL)
 		pr_err("Overwrite did not happen, but no BUG?!\n");
 	else {
 		pr_err("list_del() corruption not detected!\n");
 		pr_expected_config(CONFIG_LIST_HARDENED);
 	}
 }

 /* Test that VMAP_STACK is actually allocating with a leading guard page */
 static void lkdtm_STACK_GUARD_PAGE_LEADING(void)
 {
 	const unsigned char *stack = task_stack_page(current);
 	const unsigned char *ptr = stack - 1;
 	volatile unsigned char byte;

 	pr_info("attempting bad read from page below current stack\n");

 	byte = *ptr;

 	pr_err("FAIL: accessed page before stack! (byte: %x)\n", byte);
 }

 /* Test that VMAP_STACK is actually allocating with a trailing guard page */
 static void lkdtm_STACK_GUARD_PAGE_TRAILING(void)
 {
 	const unsigned char *stack = task_stack_page(current);
 	const unsigned char *ptr = stack + THREAD_SIZE;
 	volatile unsigned char byte;

 	pr_info("attempting bad read from page above current stack\n");

 	byte = *ptr;

 	pr_err("FAIL: accessed page after stack! (byte: %x)\n", byte);
 }

 static void lkdtm_UNSET_SMEP(void)
 {
 #if IS_ENABLED(CONFIG_X86_64) && !IS_ENABLED(CONFIG_UML)
 #define MOV_CR4_DEPTH	64
 	void (*direct_write_cr4)(unsigned long val);
 	unsigned char *insn;
 	unsigned long cr4;
 	int i;

 	cr4 = native_read_cr4();

 	if ((cr4 & X86_CR4_SMEP) != X86_CR4_SMEP) {
 		pr_err("FAIL: SMEP not in use\n");
 		return;
 	}
 	cr4 &= ~(X86_CR4_SMEP);

 	pr_info("trying to clear SMEP normally\n");
 	native_write_cr4(cr4);
 	if (cr4 == native_read_cr4()) {
 		pr_err("FAIL: pinning SMEP failed!\n");
 		cr4 |= X86_CR4_SMEP;
 		pr_info("restoring SMEP\n");
 		native_write_cr4(cr4);
 		return;
 	}
 	pr_info("ok: SMEP did not get cleared\n");

 	/*
 	 * To test the post-write pinning verification we need to call
 	 * directly into the middle of native_write_cr4() where the
 	 * cr4 write happens, skipping any pinning. This searches for
 	 * the cr4 writing instruction.
 	 */
 	insn = (unsigned char *)native_write_cr4;
 	OPTIMIZER_HIDE_VAR(insn);
 	for (i = 0; i < MOV_CR4_DEPTH; i++) {
 		/* mov %rdi, %cr4 */
 		if (insn[i] == 0x0f && insn[i+1] == 0x22 && insn[i+2] == 0xe7)
 			break;
 		/* mov %rdi,%rax; mov %rax, %cr4 */
 		if (insn[i]   == 0x48 && insn[i+1] == 0x89 &&
 		    insn[i+2] == 0xf8 && insn[i+3] == 0x0f &&
 		    insn[i+4] == 0x22 && insn[i+5] == 0xe0)
 			break;
 	}
 	if (i >= MOV_CR4_DEPTH) {
 		pr_info("ok: cannot locate cr4 writing call gadget\n");
 		return;
 	}
 	direct_write_cr4 = (void *)(insn + i);

 	pr_info("trying to clear SMEP with call gadget\n");
 	direct_write_cr4(cr4);
 	if (native_read_cr4() & X86_CR4_SMEP) {
 		pr_info("ok: SMEP removal was reverted\n");
 	} else {
 		pr_err("FAIL: cleared SMEP not detected!\n");
 		cr4 |= X86_CR4_SMEP;
 		pr_info("restoring SMEP\n");
 		native_write_cr4(cr4);
 	}
 #else
 	pr_err("XFAIL: this test is x86_64-only\n");
 #endif
 }

 static void lkdtm_DOUBLE_FAULT(void)
 {
 #if IS_ENABLED(CONFIG_X86_32) && !IS_ENABLED(CONFIG_UML)
 	/*
 	 * Trigger #DF by setting the stack limit to zero.  This clobbers
 	 * a GDT TLS slot, which is okay because the current task will die
 	 * anyway due to the double fault.
 	 */
 	struct desc_struct d = {
 		.type = 3,	/* expand-up, writable, accessed data */
 		.p = 1,		/* present */
 		.d = 1,		/* 32-bit */
 		.g = 0,		/* limit in bytes */
 		.s = 1,		/* not system */
 	};

 	local_irq_disable();
 	write_gdt_entry(get_cpu_gdt_rw(smp_processor_id()),
 			GDT_ENTRY_TLS_MIN, &d, DESCTYPE_S);

 	/*
 	 * Put our zero-limit segment in SS and then trigger a fault.  The
 	 * 4-byte access to (%esp) will fault with #SS, and the attempt to
 	 * deliver the fault will recursively cause #SS and result in #DF.
 	 * This whole process happens while NMIs and MCEs are blocked by the
 	 * MOV SS window.  This is nice because an NMI with an invalid SS
 	 * would also double-fault, resulting in the NMI or MCE being lost.
 	 */
 	asm volatile ("movw %0, %%ss; addl $0, (%%esp)" ::
 		      "r" ((unsigned short)(GDT_ENTRY_TLS_MIN << 3)));

 	pr_err("FAIL: tried to double fault but didn't die\n");
 #else
 	pr_err("XFAIL: this test is ia32-only\n");
 #endif
 }

 #ifdef CONFIG_ARM64
 static noinline void change_pac_parameters(void)
 {
 	if (IS_ENABLED(CONFIG_ARM64_PTR_AUTH_KERNEL)) {
 		/* Reset the keys of current task */
 		ptrauth_thread_init_kernel(current);
 		ptrauth_thread_switch_kernel(current);
 	}
 }
 #endif

 static noinline void lkdtm_CORRUPT_PAC(void)
 {
 #ifdef CONFIG_ARM64
 #define CORRUPT_PAC_ITERATE	10
 	int i;

 	if (!IS_ENABLED(CONFIG_ARM64_PTR_AUTH_KERNEL))
 		pr_err("FAIL: kernel not built with CONFIG_ARM64_PTR_AUTH_KERNEL\n");

 	if (!system_supports_address_auth()) {
 		pr_err("FAIL: CPU lacks pointer authentication feature\n");
 		return;
 	}

 	pr_info("changing PAC parameters to force function return failure...\n");
 	/*
 	 * PAC is a hash value computed from input keys, return address and
 	 * stack pointer. As pac has fewer bits so there is a chance of
 	 * collision, so iterate few times to reduce the collision probability.
 	 */
 	for (i = 0; i < CORRUPT_PAC_ITERATE; i++)
 		change_pac_parameters();

 	pr_err("FAIL: survived PAC changes! Kernel may be unstable from here\n");
 #else
 	pr_err("XFAIL: this test is arm64-only\n");
 #endif
 }

 static struct crashtype crashtypes[] = {
 	CRASHTYPE(PANIC),
 	CRASHTYPE(BUG),
 	CRASHTYPE(WARNING),
 	CRASHTYPE(WARNING_MESSAGE),
 	CRASHTYPE(EXCEPTION),
 	CRASHTYPE(LOOP),
 	CRASHTYPE(EXHAUST_STACK),
 	CRASHTYPE(CORRUPT_STACK),
 	CRASHTYPE(CORRUPT_STACK_STRONG),
 	CRASHTYPE(REPORT_STACK),
 	CRASHTYPE(REPORT_STACK_CANARY),
 	CRASHTYPE(UNALIGNED_LOAD_STORE_WRITE),
 	CRASHTYPE(SOFTLOCKUP),
 	CRASHTYPE(HARDLOCKUP),
 	CRASHTYPE(SPINLOCKUP),
 	CRASHTYPE(HUNG_TASK),
 	CRASHTYPE(OVERFLOW_SIGNED),
 	CRASHTYPE(OVERFLOW_UNSIGNED),
 	CRASHTYPE(ARRAY_BOUNDS),
 	CRASHTYPE(FAM_BOUNDS),
 	CRASHTYPE(CORRUPT_LIST_ADD),
 	CRASHTYPE(CORRUPT_LIST_DEL),
 	CRASHTYPE(STACK_GUARD_PAGE_LEADING),
 	CRASHTYPE(STACK_GUARD_PAGE_TRAILING),
 	CRASHTYPE(UNSET_SMEP),
 	CRASHTYPE(DOUBLE_FAULT),
 	CRASHTYPE(CORRUPT_PAC),
 };

 struct crashtype_category bugs_crashtypes = {
 	.crashtypes = crashtypes,
 	.len	    = ARRAY_SIZE(crashtypes),
 };
	// SPDX-License-Identifier: GPL-2.0
	/*
	* This is for all the tests related to logic bugs (e.g. bad dereferences,
	* bad alignment, bad loops, bad locking, bad scheduling, deep stacks, and
	* lockups) along with other things that don't fit well into existing LKDTM
	* test source files.
	*/
	#include "lkdtm.h"
	#include <linux/list.h>
	#include <linux/sched.h>
	#include <linux/sched/signal.h>
	#include <linux/sched/task_stack.h>
	#include <linux/uaccess.h>
	#include <linux/slab.h>

	#if IS_ENABLED(CONFIG_X86_32) && !IS_ENABLED(CONFIG_UML)
	#include <asm/desc.h>
	#endif

	struct lkdtm_list {
	struct list_head node;
	};

	/*
	* Make sure our attempts to over run the kernel stack doesn't trigger
	* a compiler warning when CONFIG_FRAME_WARN is set. Then make sure we
	* recurse past the end of THREAD_SIZE by default.
	*/
	#if defined(CONFIG_FRAME_WARN) && (CONFIG_FRAME_WARN > 0)
	#define REC_STACK_SIZE (_AC(CONFIG_FRAME_WARN, UL) / 2)
	#else
	#define REC_STACK_SIZE (THREAD_SIZE / 8UL)
	#endif
	#define REC_NUM_DEFAULT ((THREAD_SIZE / REC_STACK_SIZE) * 2)

	static int recur_count = REC_NUM_DEFAULT;

	static DEFINE_SPINLOCK(lock_me_up);

	/*
	* Make sure compiler does not optimize this function or stack frame away:
	* - function marked noinline
	* - stack variables are marked volatile
	* - stack variables are written (memset()) and read (buf[..] passed as arg)
	* - function may have external effects (memzero_explicit())
	* - no tail recursion possible
	*/
	static int noinline recursive_loop(int remaining)
	{
	volatile char buf[REC_STACK_SIZE];
	volatile int ret;

	memset((void *)buf, remaining & 0xFF, sizeof(buf));
	if (!remaining)
	ret = 0;
	else
	ret = recursive_loop((int)buf[remaining % sizeof(buf)] - 1);
	memzero_explicit((void *)buf, sizeof(buf));
	return ret;
	}

	/* If the depth is negative, use the default, otherwise keep parameter. */
	void __init lkdtm_bugs_init(int *recur_param)
	{
	if (*recur_param < 0)
	*recur_param = recur_count;
	else
	recur_count = *recur_param;
	}

	static void lkdtm_PANIC(void)
	{
	panic("dumptest");
	}

	static void lkdtm_BUG(void)
	{
	BUG();
	}

	static int warn_counter;

	static void lkdtm_WARNING(void)
	{
	WARN_ON(++warn_counter);
	}

	static void lkdtm_WARNING_MESSAGE(void)
	{
	WARN(1, "Warning message trigger count: %d\n", ++warn_counter);
	}

	static void lkdtm_EXCEPTION(void)
	{
	((volatile int ) 0) = 0;
	}

	static void lkdtm_LOOP(void)
	{
	for (;;)
	;
	}

	static void lkdtm_EXHAUST_STACK(void)
	{
	pr_info("Calling function with %lu frame size to depth %d ...\n",
	REC_STACK_SIZE, recur_count);
	recursive_loop(recur_count);
	pr_info("FAIL: survived without exhausting stack?!\n");
	}

	static noinline void __lkdtm_CORRUPT_STACK(void *stack)
	{
	memset(stack, '\xff', 64);
	}

	/* This should trip the stack canary, not corrupt the return address. */
	static noinline void lkdtm_CORRUPT_STACK(void)
	{
	/* Use default char array length that triggers stack protection. */
	char data[8] __aligned(sizeof(void *));

	pr_info("Corrupting stack containing char array ...\n");
	__lkdtm_CORRUPT_STACK((void *)&data);
	}

	/* Same as above but will only get a canary with -fstack-protector-strong */
	static noinline void lkdtm_CORRUPT_STACK_STRONG(void)
	{
	union {
	unsigned short shorts[4];
	unsigned long *ptr;
	} data __aligned(sizeof(void *));

	pr_info("Corrupting stack containing union ...\n");
	__lkdtm_CORRUPT_STACK((void *)&data);
	}

	static pid_t stack_pid;
	static unsigned long stack_addr;

	static void lkdtm_REPORT_STACK(void)
	{
	volatile uintptr_t magic;
	pid_t pid = task_pid_nr(current);

	if (pid != stack_pid) {
	pr_info("Starting stack offset tracking for pid %d\n", pid);
	stack_pid = pid;
	stack_addr = (uintptr_t)&magic;
	}

	pr_info("Stack offset: %d\n", (int)(stack_addr - (uintptr_t)&magic));
	}

	static pid_t stack_canary_pid;
	static unsigned long stack_canary;
	static unsigned long stack_canary_offset;

	static noinline void __lkdtm_REPORT_STACK_CANARY(void *stack)
	{
	int i = 0;
	pid_t pid = task_pid_nr(current);
	unsigned long canary = (unsigned long )stack;
	unsigned long current_offset = 0, init_offset = 0;

	/* Do our best to find the canary in a 16 word window ... */
	for (i = 1; i < 16; i++) {
	canary = (unsigned long *)stack + i;
	#ifdef CONFIG_STACKPROTECTOR
	if (*canary == current->stack_canary)
	current_offset = i;
	if (*canary == init_task.stack_canary)
	init_offset = i;
	#endif
	}

	if (current_offset == 0) {
	/*
	* If the canary doesn't match what's in the task_struct,
	* we're either using a global canary or the stack frame
	* layout changed.
	*/
	if (init_offset != 0) {
	pr_err("FAIL: global stack canary found at offset %ld (canary for pid %d matches init_task's)!\n",
	init_offset, pid);
	} else {
	pr_warn("FAIL: did not correctly locate stack canary :(\n");
	pr_expected_config(CONFIG_STACKPROTECTOR);
	}

	return;
	} else if (init_offset != 0) {
	pr_warn("WARNING: found both current and init_task canaries nearby?!\n");
	}

	canary = (unsigned long *)stack + current_offset;
	if (stack_canary_pid == 0) {
	stack_canary = *canary;
	stack_canary_pid = pid;
	stack_canary_offset = current_offset;
	pr_info("Recorded stack canary for pid %d at offset %ld\n",
	stack_canary_pid, stack_canary_offset);
	} else if (pid == stack_canary_pid) {
	pr_warn("ERROR: saw pid %d again -- please use a new pid\n", pid);
	} else {
	if (current_offset != stack_canary_offset) {
	pr_warn("ERROR: canary offset changed from %ld to %ld!?\n",
	stack_canary_offset, current_offset);
	return;
	}

	if (*canary == stack_canary) {
	pr_warn("FAIL: canary identical for pid %d and pid %d at offset %ld!\n",
	stack_canary_pid, pid, current_offset);
	} else {
	pr_info("ok: stack canaries differ between pid %d and pid %d at offset %ld.\n",
	stack_canary_pid, pid, current_offset);
	/* Reset the test. */
	stack_canary_pid = 0;
	}
	}
	}

	static void lkdtm_REPORT_STACK_CANARY(void)
	{
	/* Use default char array length that triggers stack protection. */
	char data[8] __aligned(sizeof(void *)) = { };

	__lkdtm_REPORT_STACK_CANARY((void *)&data);
	}

	static void lkdtm_UNALIGNED_LOAD_STORE_WRITE(void)
	{
	static u8 data[5] __attribute__((aligned(4))) = {1, 2, 3, 4, 5};
	u32 *p;
	u32 val = 0x12345678;

	p = (u32 *)(data + 1);
	if (*p == 0)
	val = 0x87654321;
	*p = val;

	if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
	pr_err("XFAIL: arch has CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS\n");
	}

	static void lkdtm_SOFTLOCKUP(void)
	{
	preempt_disable();
	for (;;)
	cpu_relax();
	}

	static void lkdtm_HARDLOCKUP(void)
	{
	local_irq_disable();
	for (;;)
	cpu_relax();
	}

	static void lkdtm_SPINLOCKUP(void)
	{
	/* Must be called twice to trigger. */
	spin_lock(&lock_me_up);
	/* Let sparse know we intended to exit holding the lock. */
	__release(&lock_me_up);
	}

	static void lkdtm_HUNG_TASK(void)
	{
	set_current_state(TASK_UNINTERRUPTIBLE);
	schedule();
	}

	static volatile unsigned int huge = INT_MAX - 2;
	static volatile unsigned int ignored;

	static void lkdtm_OVERFLOW_SIGNED(void)
	{
	int value;

	value = huge;
	pr_info("Normal signed addition ...\n");
	value += 1;
	ignored = value;

	pr_info("Overflowing signed addition ...\n");
	value += 4;
	ignored = value;
	}


	static void lkdtm_OVERFLOW_UNSIGNED(void)
	{
	unsigned int value;

	value = huge;
	pr_info("Normal unsigned addition ...\n");
	value += 1;
	ignored = value;

	pr_info("Overflowing unsigned addition ...\n");
	value += 4;
	ignored = value;
	}

	/* Intentionally using unannotated flex array definition. */
	struct array_bounds_flex_array {
	int one;
	int two;
	char data[];
	};

	struct array_bounds {
	int one;
	int two;
	char data[8];
	int three;
	};

	static void lkdtm_ARRAY_BOUNDS(void)
	{
	struct array_bounds_flex_array *not_checked;
	struct array_bounds *checked;
	volatile int i;

	not_checked = kmalloc(sizeof(not_checked) 2, GFP_KERNEL);
	checked = kmalloc(sizeof(checked) 2, GFP_KERNEL);
	if (!not_checked \|\| !checked) {
	kfree(not_checked);
	kfree(checked);
	return;
	}

	pr_info("Array access within bounds ...\n");
	/* For both, touch all bytes in the actual member size. */
	for (i = 0; i < sizeof(checked->data); i++)
	checked->data[i] = 'A';
	/*
	* For the uninstrumented flex array member, also touch 1 byte
	* beyond to verify it is correctly uninstrumented.
	*/
	for (i = 0; i < 2; i++)
	not_checked->data[i] = 'A';

	pr_info("Array access beyond bounds ...\n");
	for (i = 0; i < sizeof(checked->data) + 1; i++)
	checked->data[i] = 'B';

	kfree(not_checked);
	kfree(checked);
	pr_err("FAIL: survived array bounds overflow!\n");
	if (IS_ENABLED(CONFIG_UBSAN_BOUNDS))
	pr_expected_config(CONFIG_UBSAN_TRAP);
	else
	pr_expected_config(CONFIG_UBSAN_BOUNDS);
	}

	struct lkdtm_annotated {
	unsigned long flags;
	int count;
	int array[] __counted_by(count);
	};

	static volatile int fam_count = 4;

	static void lkdtm_FAM_BOUNDS(void)
	{
	struct lkdtm_annotated *inst;

	inst = kzalloc(struct_size(inst, array, fam_count + 1), GFP_KERNEL);
	if (!inst) {
	pr_err("FAIL: could not allocate test struct!\n");
	return;
	}

	inst->count = fam_count;
	pr_info("Array access within bounds ...\n");
	inst->array[1] = fam_count;
	ignored = inst->array[1];

	pr_info("Array access beyond bounds ...\n");
	inst->array[fam_count] = fam_count;
	ignored = inst->array[fam_count];

	kfree(inst);

	pr_err("FAIL: survived access of invalid flexible array member index!\n");

	if (!__has_attribute(__counted_by__))
	pr_warn("This is expected since this %s was built a compiler supporting __counted_by\n",
	lkdtm_kernel_info);
	else if (IS_ENABLED(CONFIG_UBSAN_BOUNDS))
	pr_expected_config(CONFIG_UBSAN_TRAP);
	else
	pr_expected_config(CONFIG_UBSAN_BOUNDS);
	}

	static void lkdtm_CORRUPT_LIST_ADD(void)
	{
	/*
	* Initially, an empty list via LIST_HEAD:
	* test_head.next = &test_head
	* test_head.prev = &test_head
	*/
	LIST_HEAD(test_head);
	struct lkdtm_list good, bad;
	void *target[2] = { };
	void *redirection = &target;

	pr_info("attempting good list addition\n");

	/*
	* Adding to the list performs these actions:
	* test_head.next->prev = &good.node
	* good.node.next = test_head.next
	* good.node.prev = test_head
	* test_head.next = good.node
	*/
	list_add(&good.node, &test_head);

	pr_info("attempting corrupted list addition\n");
	/*
	* In simulating this "write what where" primitive, the "what" is
	* the address of &bad.node, and the "where" is the address held
	* by "redirection".
	*/
	test_head.next = redirection;
	list_add(&bad.node, &test_head);

	if (target[0] == NULL && target[1] == NULL)
	pr_err("Overwrite did not happen, but no BUG?!\n");
	else {
	pr_err("list_add() corruption not detected!\n");
	pr_expected_config(CONFIG_LIST_HARDENED);
	}
	}

	static void lkdtm_CORRUPT_LIST_DEL(void)
	{
	LIST_HEAD(test_head);
	struct lkdtm_list item;
	void *target[2] = { };
	void *redirection = &target;

	list_add(&item.node, &test_head);

	pr_info("attempting good list removal\n");
	list_del(&item.node);

	pr_info("attempting corrupted list removal\n");
	list_add(&item.node, &test_head);

	/* As with the list_add() test above, this corrupts "next". */
	item.node.next = redirection;
	list_del(&item.node);

	if (target[0] == NULL && target[1] == NULL)
	pr_err("Overwrite did not happen, but no BUG?!\n");
	else {
	pr_err("list_del() corruption not detected!\n");
	pr_expected_config(CONFIG_LIST_HARDENED);
	}
	}

	/* Test that VMAP_STACK is actually allocating with a leading guard page */
	static void lkdtm_STACK_GUARD_PAGE_LEADING(void)
	{
	const unsigned char *stack = task_stack_page(current);
	const unsigned char *ptr = stack - 1;
	volatile unsigned char byte;

	pr_info("attempting bad read from page below current stack\n");

	byte = *ptr;

	pr_err("FAIL: accessed page before stack! (byte: %x)\n", byte);
	}

	/* Test that VMAP_STACK is actually allocating with a trailing guard page */
	static void lkdtm_STACK_GUARD_PAGE_TRAILING(void)
	{
	const unsigned char *stack = task_stack_page(current);
	const unsigned char *ptr = stack + THREAD_SIZE;
	volatile unsigned char byte;

	pr_info("attempting bad read from page above current stack\n");

	byte = *ptr;

	pr_err("FAIL: accessed page after stack! (byte: %x)\n", byte);
	}

	static void lkdtm_UNSET_SMEP(void)
	{
	#if IS_ENABLED(CONFIG_X86_64) && !IS_ENABLED(CONFIG_UML)
	#define MOV_CR4_DEPTH 64
	void (*direct_write_cr4)(unsigned long val);
	unsigned char *insn;
	unsigned long cr4;
	int i;

	cr4 = native_read_cr4();

	if ((cr4 & X86_CR4_SMEP) != X86_CR4_SMEP) {
	pr_err("FAIL: SMEP not in use\n");
	return;
	}
	cr4 &= ~(X86_CR4_SMEP);

	pr_info("trying to clear SMEP normally\n");
	native_write_cr4(cr4);
	if (cr4 == native_read_cr4()) {
	pr_err("FAIL: pinning SMEP failed!\n");
	cr4 \|= X86_CR4_SMEP;
	pr_info("restoring SMEP\n");
	native_write_cr4(cr4);
	return;
	}
	pr_info("ok: SMEP did not get cleared\n");

	/*
	* To test the post-write pinning verification we need to call
	* directly into the middle of native_write_cr4() where the
	* cr4 write happens, skipping any pinning. This searches for
	* the cr4 writing instruction.
	*/
	insn = (unsigned char *)native_write_cr4;
	OPTIMIZER_HIDE_VAR(insn);
	for (i = 0; i < MOV_CR4_DEPTH; i++) {
	/* mov %rdi, %cr4 */
	if (insn[i] == 0x0f && insn[i+1] == 0x22 && insn[i+2] == 0xe7)
	break;
	/* mov %rdi,%rax; mov %rax, %cr4 */
	if (insn[i] == 0x48 && insn[i+1] == 0x89 &&
	insn[i+2] == 0xf8 && insn[i+3] == 0x0f &&
	insn[i+4] == 0x22 && insn[i+5] == 0xe0)
	break;
	}
	if (i >= MOV_CR4_DEPTH) {
	pr_info("ok: cannot locate cr4 writing call gadget\n");
	return;
	}
	direct_write_cr4 = (void *)(insn + i);

	pr_info("trying to clear SMEP with call gadget\n");
	direct_write_cr4(cr4);
	if (native_read_cr4() & X86_CR4_SMEP) {
	pr_info("ok: SMEP removal was reverted\n");
	} else {
	pr_err("FAIL: cleared SMEP not detected!\n");
	cr4 \|= X86_CR4_SMEP;
	pr_info("restoring SMEP\n");
	native_write_cr4(cr4);
	}
	#else
	pr_err("XFAIL: this test is x86_64-only\n");
	#endif
	}

	static void lkdtm_DOUBLE_FAULT(void)
	{
	#if IS_ENABLED(CONFIG_X86_32) && !IS_ENABLED(CONFIG_UML)
	/*
	* Trigger #DF by setting the stack limit to zero. This clobbers
	* a GDT TLS slot, which is okay because the current task will die
	* anyway due to the double fault.
	*/
	struct desc_struct d = {
	.type = 3, /* expand-up, writable, accessed data */
	.p = 1, /* present */
	.d = 1, /* 32-bit */
	.g = 0, /* limit in bytes */
	.s = 1, /* not system */
	};

	local_irq_disable();
	write_gdt_entry(get_cpu_gdt_rw(smp_processor_id()),
	GDT_ENTRY_TLS_MIN, &d, DESCTYPE_S);

	/*
	* Put our zero-limit segment in SS and then trigger a fault. The
	* 4-byte access to (%esp) will fault with #SS, and the attempt to
	* deliver the fault will recursively cause #SS and result in #DF.
	* This whole process happens while NMIs and MCEs are blocked by the
	* MOV SS window. This is nice because an NMI with an invalid SS
	* would also double-fault, resulting in the NMI or MCE being lost.
	*/
	asm volatile ("movw %0, %%ss; addl $0, (%%esp)" ::
	"r" ((unsigned short)(GDT_ENTRY_TLS_MIN << 3)));

	pr_err("FAIL: tried to double fault but didn't die\n");
	#else
	pr_err("XFAIL: this test is ia32-only\n");
	#endif
	}

	#ifdef CONFIG_ARM64
	static noinline void change_pac_parameters(void)
	{
	if (IS_ENABLED(CONFIG_ARM64_PTR_AUTH_KERNEL)) {
	/* Reset the keys of current task */
	ptrauth_thread_init_kernel(current);
	ptrauth_thread_switch_kernel(current);
	}
	}
	#endif

	static noinline void lkdtm_CORRUPT_PAC(void)
	{
	#ifdef CONFIG_ARM64
	#define CORRUPT_PAC_ITERATE 10
	int i;

	if (!IS_ENABLED(CONFIG_ARM64_PTR_AUTH_KERNEL))
	pr_err("FAIL: kernel not built with CONFIG_ARM64_PTR_AUTH_KERNEL\n");

	if (!system_supports_address_auth()) {
	pr_err("FAIL: CPU lacks pointer authentication feature\n");
	return;
	}

	pr_info("changing PAC parameters to force function return failure...\n");
	/*
	* PAC is a hash value computed from input keys, return address and
	* stack pointer. As pac has fewer bits so there is a chance of
	* collision, so iterate few times to reduce the collision probability.
	*/
	for (i = 0; i < CORRUPT_PAC_ITERATE; i++)
	change_pac_parameters();

	pr_err("FAIL: survived PAC changes! Kernel may be unstable from here\n");
	#else
	pr_err("XFAIL: this test is arm64-only\n");
	#endif
	}

	static struct crashtype crashtypes[] = {
	CRASHTYPE(PANIC),
	CRASHTYPE(BUG),
	CRASHTYPE(WARNING),
	CRASHTYPE(WARNING_MESSAGE),
	CRASHTYPE(EXCEPTION),
	CRASHTYPE(LOOP),
	CRASHTYPE(EXHAUST_STACK),
	CRASHTYPE(CORRUPT_STACK),
	CRASHTYPE(CORRUPT_STACK_STRONG),
	CRASHTYPE(REPORT_STACK),
	CRASHTYPE(REPORT_STACK_CANARY),
	CRASHTYPE(UNALIGNED_LOAD_STORE_WRITE),
	CRASHTYPE(SOFTLOCKUP),
	CRASHTYPE(HARDLOCKUP),
	CRASHTYPE(SPINLOCKUP),
	CRASHTYPE(HUNG_TASK),
	CRASHTYPE(OVERFLOW_SIGNED),
	CRASHTYPE(OVERFLOW_UNSIGNED),
	CRASHTYPE(ARRAY_BOUNDS),
	CRASHTYPE(FAM_BOUNDS),
	CRASHTYPE(CORRUPT_LIST_ADD),
	CRASHTYPE(CORRUPT_LIST_DEL),
	CRASHTYPE(STACK_GUARD_PAGE_LEADING),
	CRASHTYPE(STACK_GUARD_PAGE_TRAILING),
	CRASHTYPE(UNSET_SMEP),
	CRASHTYPE(DOUBLE_FAULT),
	CRASHTYPE(CORRUPT_PAC),
	};

	struct crashtype_category bugs_crashtypes = {
	.crashtypes = crashtypes,
	.len = ARRAY_SIZE(crashtypes),
	};