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_M68K) &&            \
  35                             !defined(CONFIG_MICROBLAZE) &&      \
  36                             !defined(CONFIG_NIOS2) &&           \
  37                             !defined(CONFIG_PPC32) &&           \
  38                             !defined(CONFIG_SUPERH))
  39 # define TEST_U64
  40 #endif
  41
  42 #define test(condition, msg)            \
  43 ({                                      \
  44         int cond = (condition);         \
  45         if (cond)                       \
  46                 pr_warn("%s\n", msg);   \
  47         cond;                           \
  48 })
  49
  50 static int __init test_user_copy_init(void)
  51 {
  52         int ret = 0;
  53         char *kmem;
  54         char __user *usermem;
  55         char *bad_usermem;
  56         unsigned long user_addr;
  57         u8 val_u8;
  58         u16 val_u16;
  59         u32 val_u32;
  60 #ifdef TEST_U64
  61         u64 val_u64;
  62 #endif
  63
  64         kmem = kmalloc(PAGE_SIZE * 2, GFP_KERNEL);
  65         if (!kmem)
  66                 return -ENOMEM;
  67
  68         user_addr = vm_mmap(NULL, 0, PAGE_SIZE * 2,
  69                             PROT_READ | PROT_WRITE | PROT_EXEC,
  70                             MAP_ANONYMOUS | MAP_PRIVATE, 0);
  71         if (user_addr >= (unsigned long)(TASK_SIZE)) {
  72                 pr_warn("Failed to allocate user memory\n");
  73                 kfree(kmem);
  74                 return -ENOMEM;
  75         }
  76
  77         usermem = (char __user *)user_addr;
  78         bad_usermem = (char *)user_addr;
  79
  80         /*
  81          * Legitimate usage: none of these copies should fail.
  82          */
  83         memset(kmem, 0x3a, PAGE_SIZE * 2);
  84         ret |= test(copy_to_user(usermem, kmem, PAGE_SIZE),
  85                     "legitimate copy_to_user failed");
  86         memset(kmem, 0x0, PAGE_SIZE);
  87         ret |= test(copy_from_user(kmem, usermem, PAGE_SIZE),
  88                     "legitimate copy_from_user failed");
  89         ret |= test(memcmp(kmem, kmem + PAGE_SIZE, PAGE_SIZE),
  90                     "legitimate usercopy failed to copy data");
  91
  92 #define test_legit(size, check)                                           \
  93         do {                                                              \
  94                 val_##size = check;                                       \
  95                 ret |= test(put_user(val_##size, (size __user *)usermem), \
  96                     "legitimate put_user (" #size ") failed");            \
  97                 val_##size = 0;                                           \
  98                 ret |= test(get_user(val_##size, (size __user *)usermem), \
  99                     "legitimate get_user (" #size ") failed");            \
 100                 ret |= test(val_##size != check,                          \
 101                     "legitimate get_user (" #size ") failed to do copy"); \
 102                 if (val_##size != check) {                                \
 103                         pr_info("0x%llx != 0x%llx\n",                     \
 104                                 (unsigned long long)val_##size,           \
 105                                 (unsigned long long)check);               \
 106                 }                                                         \
 107         } while (0)
 108
 109         test_legit(u8,  0x5a);
 110         test_legit(u16, 0x5a5b);
 111         test_legit(u32, 0x5a5b5c5d);
 112 #ifdef TEST_U64
 113         test_legit(u64, 0x5a5b5c5d6a6b6c6d);
 114 #endif
 115 #undef test_legit
 116
 117         /*
 118          * Invalid usage: none of these copies should succeed.
 119          */
 120
 121         /* Prepare kernel memory with check values. */
 122         memset(kmem, 0x5a, PAGE_SIZE);
 123         memset(kmem + PAGE_SIZE, 0, PAGE_SIZE);
 124
 125         /* Reject kernel-to-kernel copies through copy_from_user(). */
 126         ret |= test(!copy_from_user(kmem, (char __user *)(kmem + PAGE_SIZE),
 127                                     PAGE_SIZE),
 128                     "illegal all-kernel copy_from_user passed");
 129
 130         /* Destination half of buffer should have been zeroed. */
 131         ret |= test(memcmp(kmem + PAGE_SIZE, kmem, PAGE_SIZE),
 132                     "zeroing failure for illegal all-kernel copy_from_user");
 133
 134 #if 0
 135         /*
 136          * When running with SMAP/PAN/etc, this will Oops the kernel
 137          * due to the zeroing of userspace memory on failure. This needs
 138          * to be tested in LKDTM instead, since this test module does not
 139          * expect to explode.
 140          */
 141         ret |= test(!copy_from_user(bad_usermem, (char __user *)kmem,
 142                                     PAGE_SIZE),
 143                     "illegal reversed copy_from_user passed");
 144 #endif
 145         ret |= test(!copy_to_user((char __user *)kmem, kmem + PAGE_SIZE,
 146                                   PAGE_SIZE),
 147                     "illegal all-kernel copy_to_user passed");
 148         ret |= test(!copy_to_user((char __user *)kmem, bad_usermem,
 149                                   PAGE_SIZE),
 150                     "illegal reversed copy_to_user passed");
 151
 152 #define test_illegal(size, check)                                           \
 153         do {                                                                \
 154                 val_##size = (check);                                       \
 155                 ret |= test(!get_user(val_##size, (size __user *)kmem),     \
 156                     "illegal get_user (" #size ") passed");                 \
 157                 ret |= test(val_##size != (size)0,                          \
 158                     "zeroing failure for illegal get_user (" #size ")");    \
 159                 if (val_##size != (size)0) {                                \
 160                         pr_info("0x%llx != 0\n",                            \
 161                                 (unsigned long long)val_##size);            \
 162                 }                                                           \
 163                 ret |= test(!put_user(val_##size, (size __user *)kmem),     \
 164                     "illegal put_user (" #size ") passed");                 \
 165         } while (0)
 166
 167         test_illegal(u8,  0x5a);
 168         test_illegal(u16, 0x5a5b);
 169         test_illegal(u32, 0x5a5b5c5d);
 170 #ifdef TEST_U64
 171         test_illegal(u64, 0x5a5b5c5d6a6b6c6d);
 172 #endif
 173 #undef test_illegal
 174
 175         vm_munmap(user_addr, PAGE_SIZE * 2);
 176         kfree(kmem);
 177
 178         if (ret == 0) {
 179                 pr_info("tests passed.\n");
 180                 return 0;
 181         }
 182
 183         return -EINVAL;
 184 }
 185
 186 module_init(test_user_copy_init);
 187
 188 static void __exit test_user_copy_exit(void)
 189 {
 190         pr_info("unloaded.\n");
 191 }
 192
 193 module_exit(test_user_copy_exit);
 194
 195 MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
 196 MODULE_LICENSE("GPL");