// SPDX-License-Identifier: GPL-2.0
/*
 * This is for all the tests related to copy_to_user() and copy_from_user()
 * hardening.
 */
#include "lkdtm.h"
#include <linux/slab.h>
#include <linux/highmem.h>
#include <linux/vmalloc.h>
#include <linux/sched/task_stack.h>
#include <linux/mman.h>
#include <linux/uaccess.h>
#include <asm/cacheflush.h>

/*
 * Many of the tests here end up using const sizes, but those would
 * normally be ignored by hardened usercopy, so force the compiler
 * into choosing the non-const path to make sure we trigger the
 * hardened usercopy checks by added "unconst" to all the const copies,
 * and making sure "cache_size" isn't optimized into a const.
 */
static volatile size_t unconst;
static volatile size_t cache_size = 1024;
static struct kmem_cache *whitelist_cache;

static const unsigned char test_text[] = "This is a test.\n";

/*
 * Instead of adding -Wno-return-local-addr, just pass the stack address
 * through a function to obfuscate it from the compiler.
 */
static noinline unsigned char *trick_compiler(unsigned char *stack)
{
        return stack + unconst;
}

static noinline unsigned char *do_usercopy_stack_callee(int value)
{
        unsigned char buf[128];
        int i;

        /* Exercise stack to avoid everything living in registers. */
        for (i = 0; i < sizeof(buf); i++) {
                buf[i] = value & 0xff;
        }

        /*
         * Put the target buffer in the middle of stack allocation
         * so that we don't step on future stack users regardless
         * of stack growth direction.
         */
        return trick_compiler(&buf[(128/2)-32]);
}

static noinline void do_usercopy_stack(bool to_user, bool bad_frame)
{
        unsigned long user_addr;
        unsigned char good_stack[32];
        unsigned char *bad_stack;
        int i;

        /* Exercise stack to avoid everything living in registers. */
        for (i = 0; i < sizeof(good_stack); i++)
                good_stack[i] = test_text[i % sizeof(test_text)];

        /* This is a pointer to outside our current stack frame. */
        if (bad_frame) {
                bad_stack = do_usercopy_stack_callee((uintptr_t)&bad_stack);
        } else {
                /* Put start address just inside stack. */
                bad_stack = task_stack_page(current) + THREAD_SIZE;
                bad_stack -= sizeof(unsigned long);
        }

#ifdef ARCH_HAS_CURRENT_STACK_POINTER
        pr_info("stack     : %px\n", (void *)current_stack_pointer);
#endif
        pr_info("good_stack: %px-%px\n", good_stack, good_stack + sizeof(good_stack));
        pr_info("bad_stack : %px-%px\n", bad_stack, bad_stack + sizeof(good_stack));

        user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
                            PROT_READ | PROT_WRITE | PROT_EXEC,
                            MAP_ANONYMOUS | MAP_PRIVATE, 0);
        if (user_addr >= TASK_SIZE) {
                pr_warn("Failed to allocate user memory\n");
                return;
        }

        if (to_user) {
                pr_info("attempting good copy_to_user of local stack\n");
                if (copy_to_user((void __user *)user_addr, good_stack,
                                 unconst + sizeof(good_stack))) {
                        pr_warn("copy_to_user failed unexpectedly?!\n");
                        goto free_user;
                }

                pr_info("attempting bad copy_to_user of distant stack\n");
                if (copy_to_user((void __user *)user_addr, bad_stack,
                                 unconst + sizeof(good_stack))) {
                        pr_warn("copy_to_user failed, but lacked Oops\n");
                        goto free_user;
                }
        } else {
                /*
                 * There isn't a safe way to not be protected by usercopy
                 * if we're going to write to another thread's stack.
                 */
                if (!bad_frame)
                        goto free_user;

                pr_info("attempting good copy_from_user of local stack\n");
                if (copy_from_user(good_stack, (void __user *)user_addr,
                                   unconst + sizeof(good_stack))) {
                        pr_warn("copy_from_user failed unexpectedly?!\n");
                        goto free_user;
                }

                pr_info("attempting bad copy_from_user of distant stack\n");
                if (copy_from_user(bad_stack, (void __user *)user_addr,
                                   unconst + sizeof(good_stack))) {
                        pr_warn("copy_from_user failed, but lacked Oops\n");
                        goto free_user;
                }
        }

free_user:
        vm_munmap(user_addr, PAGE_SIZE);
}

/*
 * This checks for whole-object size validation with hardened usercopy,
 * with or without usercopy whitelisting.
 */
static void do_usercopy_slab_size(bool to_user)
{
        unsigned long user_addr;
        unsigned char *one, *two;
        void __user *test_user_addr;
        void *test_kern_addr;
        size_t size = unconst + 1024;

        one = kmalloc(size, GFP_KERNEL);
        two = kmalloc(size, GFP_KERNEL);
        if (!one || !two) {
                pr_warn("Failed to allocate kernel memory\n");
                goto free_kernel;
        }

        user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
                            PROT_READ | PROT_WRITE | PROT_EXEC,
                            MAP_ANONYMOUS | MAP_PRIVATE, 0);
        if (user_addr >= TASK_SIZE) {
                pr_warn("Failed to allocate user memory\n");
                goto free_kernel;
        }

        memset(one, 'A', size);
        memset(two, 'B', size);

        test_user_addr = (void __user *)(user_addr + 16);
        test_kern_addr = one + 16;

        if (to_user) {
                pr_info("attempting good copy_to_user of correct size\n");
                if (copy_to_user(test_user_addr, test_kern_addr, size / 2)) {
                        pr_warn("copy_to_user failed unexpectedly?!\n");
                        goto free_user;
                }

                pr_info("attempting bad copy_to_user of too large size\n");
                if (copy_to_user(test_user_addr, test_kern_addr, size)) {
                        pr_warn("copy_to_user failed, but lacked Oops\n");
                        goto free_user;
                }
        } else {
                pr_info("attempting good copy_from_user of correct size\n");
                if (copy_from_user(test_kern_addr, test_user_addr, size / 2)) {
                        pr_warn("copy_from_user failed unexpectedly?!\n");
                        goto free_user;
                }

                pr_info("attempting bad copy_from_user of too large size\n");
                if (copy_from_user(test_kern_addr, test_user_addr, size)) {
                        pr_warn("copy_from_user failed, but lacked Oops\n");
                        goto free_user;
                }
        }
        pr_err("FAIL: bad usercopy not detected!\n");
        pr_expected_config_param(CONFIG_HARDENED_USERCOPY, "hardened_usercopy");

free_user:
        vm_munmap(user_addr, PAGE_SIZE);
free_kernel:
        kfree(one);
        kfree(two);
}

/*
 * This checks for the specific whitelist window within an object. If this
 * test passes, then do_usercopy_slab_size() tests will pass too.
 */
static void do_usercopy_slab_whitelist(bool to_user)
{
        unsigned long user_alloc;
        unsigned char *buf = NULL;
        unsigned char __user *user_addr;
        size_t offset, size;

        /* Make sure cache was prepared. */
        if (!whitelist_cache) {
                pr_warn("Failed to allocate kernel cache\n");
                return;
        }

        /*
         * Allocate a buffer with a whitelisted window in the buffer.
         */
        buf = kmem_cache_alloc(whitelist_cache, GFP_KERNEL);
        if (!buf) {
                pr_warn("Failed to allocate buffer from whitelist cache\n");
                goto free_alloc;
        }

        /* Allocate user memory we'll poke at. */
        user_alloc = vm_mmap(NULL, 0, PAGE_SIZE,
                            PROT_READ | PROT_WRITE | PROT_EXEC,
                            MAP_ANONYMOUS | MAP_PRIVATE, 0);
        if (user_alloc >= TASK_SIZE) {
                pr_warn("Failed to allocate user memory\n");
                goto free_alloc;
        }
        user_addr = (void __user *)user_alloc;

        memset(buf, 'B', cache_size);

        /* Whitelisted window in buffer, from kmem_cache_create_usercopy. */
        offset = (cache_size / 4) + unconst;
        size = (cache_size / 16) + unconst;

        if (to_user) {
                pr_info("attempting good copy_to_user inside whitelist\n");
                if (copy_to_user(user_addr, buf + offset, size)) {
                        pr_warn("copy_to_user failed unexpectedly?!\n");
                        goto free_user;
                }

                pr_info("attempting bad copy_to_user outside whitelist\n");
                if (copy_to_user(user_addr, buf + offset - 1, size)) {
                        pr_warn("copy_to_user failed, but lacked Oops\n");
                        goto free_user;
                }
        } else {
                pr_info("attempting good copy_from_user inside whitelist\n");
                if (copy_from_user(buf + offset, user_addr, size)) {
                        pr_warn("copy_from_user failed unexpectedly?!\n");
                        goto free_user;
                }

                pr_info("attempting bad copy_from_user outside whitelist\n");
                if (copy_from_user(buf + offset - 1, user_addr, size)) {
                        pr_warn("copy_from_user failed, but lacked Oops\n");
                        goto free_user;
                }
        }
        pr_err("FAIL: bad usercopy not detected!\n");
        pr_expected_config_param(CONFIG_HARDENED_USERCOPY, "hardened_usercopy");

free_user:
        vm_munmap(user_alloc, PAGE_SIZE);
free_alloc:
        if (buf)
                kmem_cache_free(whitelist_cache, buf);
}

/* Callable tests. */
static void lkdtm_USERCOPY_SLAB_SIZE_TO(void)
{
        do_usercopy_slab_size(true);
}

static void lkdtm_USERCOPY_SLAB_SIZE_FROM(void)
{
        do_usercopy_slab_size(false);
}

static void lkdtm_USERCOPY_SLAB_WHITELIST_TO(void)
{
        do_usercopy_slab_whitelist(true);
}

static void lkdtm_USERCOPY_SLAB_WHITELIST_FROM(void)
{
        do_usercopy_slab_whitelist(false);
}

static void lkdtm_USERCOPY_STACK_FRAME_TO(void)
{
        do_usercopy_stack(true, true);
}

static void lkdtm_USERCOPY_STACK_FRAME_FROM(void)
{
        do_usercopy_stack(false, true);
}

static void lkdtm_USERCOPY_STACK_BEYOND(void)
{
        do_usercopy_stack(true, false);
}

static void lkdtm_USERCOPY_KERNEL(void)
{
        unsigned long user_addr;

        user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
                            PROT_READ | PROT_WRITE | PROT_EXEC,
                            MAP_ANONYMOUS | MAP_PRIVATE, 0);
        if (user_addr >= TASK_SIZE) {
                pr_warn("Failed to allocate user memory\n");
                return;
        }

        pr_info("attempting good copy_to_user from kernel rodata: %px\n",
                test_text);
        if (copy_to_user((void __user *)user_addr, test_text,
                         unconst + sizeof(test_text))) {
                pr_warn("copy_to_user failed unexpectedly?!\n");
                goto free_user;
        }

        pr_info("attempting bad copy_to_user from kernel text: %px\n",
                vm_mmap);
        if (copy_to_user((void __user *)user_addr, vm_mmap,
                         unconst + PAGE_SIZE)) {
                pr_warn("copy_to_user failed, but lacked Oops\n");
                goto free_user;
        }
        pr_err("FAIL: bad copy_to_user() not detected!\n");
        pr_expected_config_param(CONFIG_HARDENED_USERCOPY, "hardened_usercopy");

free_user:
        vm_munmap(user_addr, PAGE_SIZE);
}

/*
 * This expects "kaddr" to point to a PAGE_SIZE allocation, which means
 * a more complete test that would include copy_from_user() would risk
 * memory corruption. Just test copy_to_user() here, as that exercises
 * almost exactly the same code paths.
 */
static void do_usercopy_page_span(const char *name, void *kaddr)
{
        unsigned long uaddr;

        uaddr = vm_mmap(NULL, 0, PAGE_SIZE, PROT_READ | PROT_WRITE,
                        MAP_ANONYMOUS | MAP_PRIVATE, 0);
        if (uaddr >= TASK_SIZE) {
                pr_warn("Failed to allocate user memory\n");
                return;
        }

        /* Initialize contents. */
        memset(kaddr, 0xAA, PAGE_SIZE);

        /* Bump the kaddr forward to detect a page-spanning overflow. */
        kaddr += PAGE_SIZE / 2;

        pr_info("attempting good copy_to_user() from kernel %s: %px\n",
                name, kaddr);
        if (copy_to_user((void __user *)uaddr, kaddr,
                         unconst + (PAGE_SIZE / 2))) {
                pr_err("copy_to_user() failed unexpectedly?!\n");
                goto free_user;
        }

        pr_info("attempting bad copy_to_user() from kernel %s: %px\n",
                name, kaddr);
        if (copy_to_user((void __user *)uaddr, kaddr, unconst + PAGE_SIZE)) {
                pr_warn("Good, copy_to_user() failed, but lacked Oops(?!)\n");
                goto free_user;
        }

        pr_err("FAIL: bad copy_to_user() not detected!\n");
        pr_expected_config_param(CONFIG_HARDENED_USERCOPY, "hardened_usercopy");

free_user:
        vm_munmap(uaddr, PAGE_SIZE);
}

static void lkdtm_USERCOPY_VMALLOC(void)
{
        void *addr;

        addr = vmalloc(PAGE_SIZE);
        if (!addr) {
                pr_err("vmalloc() failed!?\n");
                return;
        }
        do_usercopy_page_span("vmalloc", addr);
        vfree(addr);
}

static void lkdtm_USERCOPY_FOLIO(void)
{
        struct folio *folio;
        void *addr;

        /*
         * FIXME: Folio checking currently misses 0-order allocations, so
         * allocate and bump forward to the last page.
         */
        folio = folio_alloc(GFP_KERNEL | __GFP_ZERO, 1);
        if (!folio) {
                pr_err("folio_alloc() failed!?\n");
                return;
        }
        addr = folio_address(folio);
        if (addr)
                do_usercopy_page_span("folio", addr + PAGE_SIZE);
        else
                pr_err("folio_address() failed?!\n");
        folio_put(folio);
}

void __init lkdtm_usercopy_init(void)
{
        /* Prepare cache that lacks SLAB_USERCOPY flag. */
        whitelist_cache =
                kmem_cache_create_usercopy("lkdtm-usercopy", cache_size,
                                           0, 0,
                                           cache_size / 4,
                                           cache_size / 16,
                                           NULL);
}

void __exit lkdtm_usercopy_exit(void)
{
        kmem_cache_destroy(whitelist_cache);
}

static struct crashtype crashtypes[] = {
        CRASHTYPE(USERCOPY_SLAB_SIZE_TO),
        CRASHTYPE(USERCOPY_SLAB_SIZE_FROM),
        CRASHTYPE(USERCOPY_SLAB_WHITELIST_TO),
        CRASHTYPE(USERCOPY_SLAB_WHITELIST_FROM),
        CRASHTYPE(USERCOPY_STACK_FRAME_TO),
        CRASHTYPE(USERCOPY_STACK_FRAME_FROM),
        CRASHTYPE(USERCOPY_STACK_BEYOND),
        CRASHTYPE(USERCOPY_VMALLOC),
        CRASHTYPE(USERCOPY_FOLIO),
        CRASHTYPE(USERCOPY_KERNEL),
};

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