Merge tag 'trace-printf-v6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/trace...

[drm/drm-misc.git] / drivers / misc / lkdtm / bugs.c

// 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/cpu.h>
#include <linux/list.h>
#include <linux/sched.h>
#include <linux/sched/signal.h>
#include <linux/sched/task_stack.h>
#include <linux/slab.h>
#include <linux/stop_machine.h>
#include <linux/uaccess.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 int panic_stop_irqoff_fn(void *arg)
{
        atomic_t *v = arg;

        /*
         * As stop_machine() disables interrupts, all CPUs within this function
         * have interrupts disabled and cannot take a regular IPI.
         *
         * The last CPU which enters here will trigger a panic, and as all CPUs
         * cannot take a regular IPI, we'll only be able to stop secondaries if
         * smp_send_stop() or crash_smp_send_stop() uses an NMI.
         */
        if (atomic_inc_return(v) == num_online_cpus())
                panic("panic stop irqoff test");

        for (;;)
                cpu_relax();
}

static void lkdtm_PANIC_STOP_IRQOFF(void)
{
        atomic_t v = ATOMIC_INIT(0);
        stop_machine(panic_stop_irqoff_fn, &v, cpu_online_mask);
}

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_SMP_CALL_LOCKUP(void *unused)
{
        for (;;)
                cpu_relax();
}

static void lkdtm_SMP_CALL_LOCKUP(void)
{
        unsigned int cpu, target;

        cpus_read_lock();

        cpu = get_cpu();
        target = cpumask_any_but(cpu_online_mask, cpu);

        if (target >= nr_cpu_ids) {
                pr_err("FAIL: no other online CPUs\n");
                goto out_put_cpus;
        }

        smp_call_function_single(target, __lkdtm_SMP_CALL_LOCKUP, NULL, 1);

        pr_err("FAIL: did not hang\n");

out_put_cpus:
        put_cpu();
        cpus_read_unlock();
}

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 __noreturn lkdtm_HUNG_TASK(void)
{
        set_current_state(TASK_UNINTERRUPTIBLE);
        schedule();
        BUG();
}

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 (!IS_ENABLED(CONFIG_CC_HAS_COUNTED_BY))
                pr_warn("This is expected since this %s was built with a compiler that does not support __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(PANIC_STOP_IRQOFF),
        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(SMP_CALL_LOCKUP),
        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),
};