/*
 * Kernel module for testing copy_to/from_user infrastructure.
 *
 * Copyright 2013 Google Inc. All Rights Reserved
 *
 * Authors:
 *      Kees Cook       <keescook@chromium.org>
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/mman.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/vmalloc.h>

/*
 * Several 32-bit architectures support 64-bit {get,put}_user() calls.
 * As there doesn't appear to be anything that can safely determine
 * their capability at compile-time, we just have to opt-out certain archs.
 */
#if BITS_PER_LONG == 64 || (!(defined(CONFIG_ARM) && !defined(MMU)) && \
                            !defined(CONFIG_M68K) &&            \
                            !defined(CONFIG_MICROBLAZE) &&      \
                            !defined(CONFIG_NIOS2) &&           \
                            !defined(CONFIG_PPC32) &&           \
                            !defined(CONFIG_SUPERH))
# define TEST_U64
#endif

#define test(condition, msg)            \
({                                      \
        int cond = (condition);         \
        if (cond)                       \
                pr_warn("%s\n", msg);   \
        cond;                           \
})

static int __init test_user_copy_init(void)
{
        int ret = 0;
        char *kmem;
        char __user *usermem;
        char *bad_usermem;
        unsigned long user_addr;
        u8 val_u8;
        u16 val_u16;
        u32 val_u32;
#ifdef TEST_U64
        u64 val_u64;
#endif

        kmem = kmalloc(PAGE_SIZE * 2, GFP_KERNEL);
        if (!kmem)
                return -ENOMEM;

        user_addr = vm_mmap(NULL, 0, PAGE_SIZE * 2,
                            PROT_READ | PROT_WRITE | PROT_EXEC,
                            MAP_ANONYMOUS | MAP_PRIVATE, 0);
        if (user_addr >= (unsigned long)(TASK_SIZE)) {
                pr_warn("Failed to allocate user memory\n");
                kfree(kmem);
                return -ENOMEM;
        }

        usermem = (char __user *)user_addr;
        bad_usermem = (char *)user_addr;

        /*
         * Legitimate usage: none of these copies should fail.
         */
        memset(kmem, 0x3a, PAGE_SIZE * 2);
        ret |= test(copy_to_user(usermem, kmem, PAGE_SIZE),
                    "legitimate copy_to_user failed");
        memset(kmem, 0x0, PAGE_SIZE);
        ret |= test(copy_from_user(kmem, usermem, PAGE_SIZE),
                    "legitimate copy_from_user failed");
        ret |= test(memcmp(kmem, kmem + PAGE_SIZE, PAGE_SIZE),
                    "legitimate usercopy failed to copy data");

#define test_legit(size, check)                                           \
        do {                                                              \
                val_##size = check;                                       \
                ret |= test(put_user(val_##size, (size __user *)usermem), \
                    "legitimate put_user (" #size ") failed");            \
                val_##size = 0;                                           \
                ret |= test(get_user(val_##size, (size __user *)usermem), \
                    "legitimate get_user (" #size ") failed");            \
                ret |= test(val_##size != check,                          \
                    "legitimate get_user (" #size ") failed to do copy"); \
                if (val_##size != check) {                                \
                        pr_info("0x%llx != 0x%llx\n",                     \
                                (unsigned long long)val_##size,           \
                                (unsigned long long)check);               \
                }                                                         \
        } while (0)

        test_legit(u8,  0x5a);
        test_legit(u16, 0x5a5b);
        test_legit(u32, 0x5a5b5c5d);
#ifdef TEST_U64
        test_legit(u64, 0x5a5b5c5d6a6b6c6d);
#endif
#undef test_legit

        /*
         * Invalid usage: none of these copies should succeed.
         */

        /* Prepare kernel memory with check values. */
        memset(kmem, 0x5a, PAGE_SIZE);
        memset(kmem + PAGE_SIZE, 0, PAGE_SIZE);

        /* Reject kernel-to-kernel copies through copy_from_user(). */
        ret |= test(!copy_from_user(kmem, (char __user *)(kmem + PAGE_SIZE),
                                    PAGE_SIZE),
                    "illegal all-kernel copy_from_user passed");

        /* Destination half of buffer should have been zeroed. */
        ret |= test(memcmp(kmem + PAGE_SIZE, kmem, PAGE_SIZE),
                    "zeroing failure for illegal all-kernel copy_from_user");

#if 0
        /*
         * When running with SMAP/PAN/etc, this will Oops the kernel
         * due to the zeroing of userspace memory on failure. This needs
         * to be tested in LKDTM instead, since this test module does not
         * expect to explode.
         */
        ret |= test(!copy_from_user(bad_usermem, (char __user *)kmem,
                                    PAGE_SIZE),
                    "illegal reversed copy_from_user passed");
#endif
        ret |= test(!copy_to_user((char __user *)kmem, kmem + PAGE_SIZE,
                                  PAGE_SIZE),
                    "illegal all-kernel copy_to_user passed");
        ret |= test(!copy_to_user((char __user *)kmem, bad_usermem,
                                  PAGE_SIZE),
                    "illegal reversed copy_to_user passed");

#define test_illegal(size, check)                                           \
        do {                                                                \
                val_##size = (check);                                       \
                ret |= test(!get_user(val_##size, (size __user *)kmem),     \
                    "illegal get_user (" #size ") passed");                 \
                ret |= test(val_##size != (size)0,                          \
                    "zeroing failure for illegal get_user (" #size ")");    \
                if (val_##size != (size)0) {                                \
                        pr_info("0x%llx != 0\n",                            \
                                (unsigned long long)val_##size);            \
                }                                                           \
                ret |= test(!put_user(val_##size, (size __user *)kmem),     \
                    "illegal put_user (" #size ") passed");                 \
        } while (0)

        test_illegal(u8,  0x5a);
        test_illegal(u16, 0x5a5b);
        test_illegal(u32, 0x5a5b5c5d);
#ifdef TEST_U64
        test_illegal(u64, 0x5a5b5c5d6a6b6c6d);
#endif
#undef test_illegal

        vm_munmap(user_addr, PAGE_SIZE * 2);
        kfree(kmem);

        if (ret == 0) {
                pr_info("tests passed.\n");
                return 0;
        }

        return -EINVAL;
}

module_init(test_user_copy_init);

static void __exit test_user_copy_exit(void)
{
        pr_info("unloaded.\n");
}

module_exit(test_user_copy_exit);

MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
MODULE_LICENSE("GPL");