lib/test_user_copy.c

   1 /*
   2  * Kernel module for testing copy_to/from_user infrastructure.
   3  *
   4  * Copyright 2013 Google Inc. All Rights Reserved
   5  *
   6  * Authors:
   7  *      Kees Cook       <keescook@chromium.org>
   8  *
   9  * This software is licensed under the terms of the GNU General Public
  10  * License version 2, as published by the Free Software Foundation, and
  11  * may be copied, distributed, and modified under those terms.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  */
  18
  19 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  20
  21 #include <linux/mman.h>
  22 #include <linux/module.h>
  23 #include <linux/sched.h>
  24 #include <linux/slab.h>
  25 #include <linux/uaccess.h>
  26 #include <linux/vmalloc.h>
  27
  28 /*
  29  * Several 32-bit architectures support 64-bit {get,put}_user() calls.
  30  * As there doesn't appear to be anything that can safely determine
  31  * their capability at compile-time, we just have to opt-out certain archs.
  32  */
  33 #if BITS_PER_LONG == 64 || (!(defined(CONFIG_ARM) && !defined(MMU)) && \
  34                             !defined(CONFIG_BLACKFIN) &&        \
  35                             !defined(CONFIG_M32R) &&            \
  36                             !defined(CONFIG_M68K) &&            \
  37                             !defined(CONFIG_MICROBLAZE) &&      \
  38                             !defined(CONFIG_MN10300) &&         \
  39                             !defined(CONFIG_NIOS2) &&           \
  40                             !defined(CONFIG_PPC32) &&           \
  41                             !defined(CONFIG_SUPERH))
  42 # define TEST_U64
  43 #endif
  44
  45 #define test(condition, msg)            \
  46 ({                                      \
  47         int cond = (condition);         \
  48         if (cond)                       \
  49                 pr_warn("%s\n", msg);   \
  50         cond;                           \
  51 })
  52
  53 static int __init test_user_copy_init(void)
  54 {
  55         int ret = 0;
  56         char *kmem;
  57         char __user *usermem;
  58         char *bad_usermem;
  59         unsigned long user_addr;
  60         u8 val_u8;
  61         u16 val_u16;
  62         u32 val_u32;
  63 #ifdef TEST_U64
  64         u64 val_u64;
  65 #endif
  66
  67         kmem = kmalloc(PAGE_SIZE * 2, GFP_KERNEL);
  68         if (!kmem)
  69                 return -ENOMEM;
  70
  71         user_addr = vm_mmap(NULL, 0, PAGE_SIZE * 2,
  72                             PROT_READ | PROT_WRITE | PROT_EXEC,
  73                             MAP_ANONYMOUS | MAP_PRIVATE, 0);
  74         if (user_addr >= (unsigned long)(TASK_SIZE)) {
  75                 pr_warn("Failed to allocate user memory\n");
  76                 kfree(kmem);
  77                 return -ENOMEM;
  78         }
  79
  80         usermem = (char __user *)user_addr;
  81         bad_usermem = (char *)user_addr;
  82
  83         /*
  84          * Legitimate usage: none of these copies should fail.
  85          */
  86         memset(kmem, 0x3a, PAGE_SIZE * 2);
  87         ret |= test(copy_to_user(usermem, kmem, PAGE_SIZE),
  88                     "legitimate copy_to_user failed");
  89         memset(kmem, 0x0, PAGE_SIZE);
  90         ret |= test(copy_from_user(kmem, usermem, PAGE_SIZE),
  91                     "legitimate copy_from_user failed");
  92         ret |= test(memcmp(kmem, kmem + PAGE_SIZE, PAGE_SIZE),
  93                     "legitimate usercopy failed to copy data");
  94
  95 #define test_legit(size, check)                                           \
  96         do {                                                              \
  97                 val_##size = check;                                       \
  98                 ret |= test(put_user(val_##size, (size __user *)usermem), \
  99                     "legitimate put_user (" #size ") failed");            \
 100                 val_##size = 0;                                           \
 101                 ret |= test(get_user(val_##size, (size __user *)usermem), \
 102                     "legitimate get_user (" #size ") failed");            \
 103                 ret |= test(val_##size != check,                          \
 104                     "legitimate get_user (" #size ") failed to do copy"); \
 105                 if (val_##size != check) {                                \
 106                         pr_info("0x%llx != 0x%llx\n",                     \
 107                                 (unsigned long long)val_##size,           \
 108                                 (unsigned long long)check);               \
 109                 }                                                         \
 110         } while (0)
 111
 112         test_legit(u8,  0x5a);
 113         test_legit(u16, 0x5a5b);
 114         test_legit(u32, 0x5a5b5c5d);
 115 #ifdef TEST_U64
 116         test_legit(u64, 0x5a5b5c5d6a6b6c6d);
 117 #endif
 118 #undef test_legit
 119
 120         /*
 121          * Invalid usage: none of these copies should succeed.
 122          */
 123
 124         /* Prepare kernel memory with check values. */
 125         memset(kmem, 0x5a, PAGE_SIZE);
 126         memset(kmem + PAGE_SIZE, 0, PAGE_SIZE);
 127
 128         /* Reject kernel-to-kernel copies through copy_from_user(). */
 129         ret |= test(!copy_from_user(kmem, (char __user *)(kmem + PAGE_SIZE),
 130                                     PAGE_SIZE),
 131                     "illegal all-kernel copy_from_user passed");
 132
 133         /* Destination half of buffer should have been zeroed. */
 134         ret |= test(memcmp(kmem + PAGE_SIZE, kmem, PAGE_SIZE),
 135                     "zeroing failure for illegal all-kernel copy_from_user");
 136
 137 #if 0
 138         /*
 139          * When running with SMAP/PAN/etc, this will Oops the kernel
 140          * due to the zeroing of userspace memory on failure. This needs
 141          * to be tested in LKDTM instead, since this test module does not
 142          * expect to explode.
 143          */
 144         ret |= test(!copy_from_user(bad_usermem, (char __user *)kmem,
 145                                     PAGE_SIZE),
 146                     "illegal reversed copy_from_user passed");
 147 #endif
 148         ret |= test(!copy_to_user((char __user *)kmem, kmem + PAGE_SIZE,
 149                                   PAGE_SIZE),
 150                     "illegal all-kernel copy_to_user passed");
 151         ret |= test(!copy_to_user((char __user *)kmem, bad_usermem,
 152                                   PAGE_SIZE),
 153                     "illegal reversed copy_to_user passed");
 154
 155 #define test_illegal(size, check)                                           \
 156         do {                                                                \
 157                 val_##size = (check);                                       \
 158                 ret |= test(!get_user(val_##size, (size __user *)kmem),     \
 159                     "illegal get_user (" #size ") passed");                 \
 160                 ret |= test(val_##size != (size)0,                          \
 161                     "zeroing failure for illegal get_user (" #size ")");    \
 162                 if (val_##size != (size)0) {                                \
 163                         pr_info("0x%llx != 0\n",                            \
 164                                 (unsigned long long)val_##size);            \
 165                 }                                                           \
 166                 ret |= test(!put_user(val_##size, (size __user *)kmem),     \
 167                     "illegal put_user (" #size ") passed");                 \
 168         } while (0)
 169
 170         test_illegal(u8,  0x5a);
 171         test_illegal(u16, 0x5a5b);
 172         test_illegal(u32, 0x5a5b5c5d);
 173 #ifdef TEST_U64
 174         test_illegal(u64, 0x5a5b5c5d6a6b6c6d);
 175 #endif
 176 #undef test_illegal
 177
 178         vm_munmap(user_addr, PAGE_SIZE * 2);
 179         kfree(kmem);
 180
 181         if (ret == 0) {
 182                 pr_info("tests passed.\n");
 183                 return 0;
 184         }
 185
 186         return -EINVAL;
 187 }
 188
 189 module_init(test_user_copy_init);
 190
 191 static void __exit test_user_copy_exit(void)
 192 {
 193         pr_info("unloaded.\n");
 194 }
 195
 196 module_exit(test_user_copy_exit);
 197
 198 MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
 199 MODULE_LICENSE("GPL");