// 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>
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 (CONFIG_FRAME_WARN / 2)
#else
#define REC_STACK_SIZE (THREAD_SIZE / 8)
#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 (pr_info())
* - function has external effects (pr_info())
* */
static int noinline recursive_loop(int remaining)
{
volatile char buf[REC_STACK_SIZE];
memset((void *)buf, remaining & 0xFF, sizeof(buf));
pr_info("loop %d/%d ...\n", (int)buf[remaining % sizeof(buf)],
recur_count);
if (!remaining)
return 0;
else
return recursive_loop(remaining - 1);
}
/* 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;
}
void lkdtm_PANIC(void)
{
panic("dumptest");
}
void lkdtm_BUG(void)
{
BUG();
}
static int warn_counter;
void lkdtm_WARNING(void)
{
WARN(1, "Warning message trigger count: %d\n", warn_counter++);
}
void lkdtm_EXCEPTION(void)
{
*((volatile int *) 0) = 0;
}
void lkdtm_LOOP(void)
{
for (;;)
;
}
void lkdtm_EXHAUST_STACK(void)
{
pr_info("Calling function with %d 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. */
noinline void lkdtm_CORRUPT_STACK(void)
{
/* Use default char array length that triggers stack protection. */
char data[8] __aligned(sizeof(void *));
__lkdtm_CORRUPT_STACK(&data);
pr_info("Corrupted stack containing char array ...\n");
}
/* Same as above but will only get a canary with -fstack-protector-strong */
noinline void lkdtm_CORRUPT_STACK_STRONG(void)
{
union {
unsigned short shorts[4];
unsigned long *ptr;
} data __aligned(sizeof(void *));
__lkdtm_CORRUPT_STACK(&data);
pr_info("Corrupted stack containing union ...\n");
}
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;
}
void lkdtm_SOFTLOCKUP(void)
{
preempt_disable();
for (;;)
cpu_relax();
}
void lkdtm_HARDLOCKUP(void)
{
local_irq_disable();
for (;;)
cpu_relax();
}
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);
}
void lkdtm_HUNG_TASK(void)
{
set_current_state(TASK_UNINTERRUPTIBLE);
schedule();
}
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 = ⌖
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");
}
void lkdtm_CORRUPT_LIST_DEL(void)
{
LIST_HEAD(test_head);
struct lkdtm_list item;
void *target[2] = { };
void *redirection = ⌖
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");
}
/* Test if unbalanced set_fs(KERNEL_DS)/set_fs(USER_DS) check exists. */
void lkdtm_CORRUPT_USER_DS(void)
{
pr_info("setting bad task size limit\n");
set_fs(KERNEL_DS);
/* Make sure we do not keep running with a KERNEL_DS! */
force_sig(SIGKILL);
}
/* Test that VMAP_STACK is actually allocating with a leading guard page */
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!\n");
}
/* Test that VMAP_STACK is actually allocating with a trailing guard page */
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!\n");
}
