lib/test_user_copy.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Kernel module for testing copy_to/from_user infrastructure.
   4  *
   5  * Copyright 2013 Google Inc. All Rights Reserved
   6  *
   7  * Authors:
   8  *      Kees Cook       <keescook@chromium.org>
   9  */
  10
  11 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  12
  13 #include <linux/mman.h>
  14 #include <linux/module.h>
  15 #include <linux/sched.h>
  16 #include <linux/slab.h>
  17 #include <linux/uaccess.h>
  18 #include <linux/vmalloc.h>
  19
  20 /*
  21  * Several 32-bit architectures support 64-bit {get,put}_user() calls.
  22  * As there doesn't appear to be anything that can safely determine
  23  * their capability at compile-time, we just have to opt-out certain archs.
  24  */
  25 #if BITS_PER_LONG == 64 || (!(defined(CONFIG_ARM) && !defined(MMU)) && \
  26                             !defined(CONFIG_M68K) &&            \
  27                             !defined(CONFIG_MICROBLAZE) &&      \
  28                             !defined(CONFIG_NIOS2) &&           \
  29                             !defined(CONFIG_PPC32) &&           \
  30                             !defined(CONFIG_SUPERH))
  31 # define TEST_U64
  32 #endif
  33
  34 #define test(condition, msg)            \
  35 ({                                      \
  36         int cond = (condition);         \
  37         if (cond)                       \
  38                 pr_warn("%s\n", msg);   \
  39         cond;                           \
  40 })
  41
  42 static int __init test_user_copy_init(void)
  43 {
  44         int ret = 0;
  45         char *kmem;
  46         char __user *usermem;
  47         char *bad_usermem;
  48         unsigned long user_addr;
  49         u8 val_u8;
  50         u16 val_u16;
  51         u32 val_u32;
  52 #ifdef TEST_U64
  53         u64 val_u64;
  54 #endif
  55
  56         kmem = kmalloc(PAGE_SIZE * 2, GFP_KERNEL);
  57         if (!kmem)
  58                 return -ENOMEM;
  59
  60         user_addr = vm_mmap(NULL, 0, PAGE_SIZE * 2,
  61                             PROT_READ | PROT_WRITE | PROT_EXEC,
  62                             MAP_ANONYMOUS | MAP_PRIVATE, 0);
  63         if (user_addr >= (unsigned long)(TASK_SIZE)) {
  64                 pr_warn("Failed to allocate user memory\n");
  65                 kfree(kmem);
  66                 return -ENOMEM;
  67         }
  68
  69         usermem = (char __user *)user_addr;
  70         bad_usermem = (char *)user_addr;
  71
  72         /*
  73          * Legitimate usage: none of these copies should fail.
  74          */
  75         memset(kmem, 0x3a, PAGE_SIZE * 2);
  76         ret |= test(copy_to_user(usermem, kmem, PAGE_SIZE),
  77                     "legitimate copy_to_user failed");
  78         memset(kmem, 0x0, PAGE_SIZE);
  79         ret |= test(copy_from_user(kmem, usermem, PAGE_SIZE),
  80                     "legitimate copy_from_user failed");
  81         ret |= test(memcmp(kmem, kmem + PAGE_SIZE, PAGE_SIZE),
  82                     "legitimate usercopy failed to copy data");
  83
  84 #define test_legit(size, check)                                           \
  85         do {                                                              \
  86                 val_##size = check;                                       \
  87                 ret |= test(put_user(val_##size, (size __user *)usermem), \
  88                     "legitimate put_user (" #size ") failed");            \
  89                 val_##size = 0;                                           \
  90                 ret |= test(get_user(val_##size, (size __user *)usermem), \
  91                     "legitimate get_user (" #size ") failed");            \
  92                 ret |= test(val_##size != check,                          \
  93                     "legitimate get_user (" #size ") failed to do copy"); \
  94                 if (val_##size != check) {                                \
  95                         pr_info("0x%llx != 0x%llx\n",                     \
  96                                 (unsigned long long)val_##size,           \
  97                                 (unsigned long long)check);               \
  98                 }                                                         \
  99         } while (0)
 100
 101         test_legit(u8,  0x5a);
 102         test_legit(u16, 0x5a5b);
 103         test_legit(u32, 0x5a5b5c5d);
 104 #ifdef TEST_U64
 105         test_legit(u64, 0x5a5b5c5d6a6b6c6d);
 106 #endif
 107 #undef test_legit
 108
 109         /*
 110          * Invalid usage: none of these copies should succeed.
 111          */
 112
 113         /* Prepare kernel memory with check values. */
 114         memset(kmem, 0x5a, PAGE_SIZE);
 115         memset(kmem + PAGE_SIZE, 0, PAGE_SIZE);
 116
 117         /* Reject kernel-to-kernel copies through copy_from_user(). */
 118         ret |= test(!copy_from_user(kmem, (char __user *)(kmem + PAGE_SIZE),
 119                                     PAGE_SIZE),
 120                     "illegal all-kernel copy_from_user passed");
 121
 122         /* Destination half of buffer should have been zeroed. */
 123         ret |= test(memcmp(kmem + PAGE_SIZE, kmem, PAGE_SIZE),
 124                     "zeroing failure for illegal all-kernel copy_from_user");
 125
 126 #if 0
 127         /*
 128          * When running with SMAP/PAN/etc, this will Oops the kernel
 129          * due to the zeroing of userspace memory on failure. This needs
 130          * to be tested in LKDTM instead, since this test module does not
 131          * expect to explode.
 132          */
 133         ret |= test(!copy_from_user(bad_usermem, (char __user *)kmem,
 134                                     PAGE_SIZE),
 135                     "illegal reversed copy_from_user passed");
 136 #endif
 137         ret |= test(!copy_to_user((char __user *)kmem, kmem + PAGE_SIZE,
 138                                   PAGE_SIZE),
 139                     "illegal all-kernel copy_to_user passed");
 140         ret |= test(!copy_to_user((char __user *)kmem, bad_usermem,
 141                                   PAGE_SIZE),
 142                     "illegal reversed copy_to_user passed");
 143
 144 #define test_illegal(size, check)                                           \
 145         do {                                                                \
 146                 val_##size = (check);                                       \
 147                 ret |= test(!get_user(val_##size, (size __user *)kmem),     \
 148                     "illegal get_user (" #size ") passed");                 \
 149                 ret |= test(val_##size != (size)0,                          \
 150                     "zeroing failure for illegal get_user (" #size ")");    \
 151                 if (val_##size != (size)0) {                                \
 152                         pr_info("0x%llx != 0\n",                            \
 153                                 (unsigned long long)val_##size);            \
 154                 }                                                           \
 155                 ret |= test(!put_user(val_##size, (size __user *)kmem),     \
 156                     "illegal put_user (" #size ") passed");                 \
 157         } while (0)
 158
 159         test_illegal(u8,  0x5a);
 160         test_illegal(u16, 0x5a5b);
 161         test_illegal(u32, 0x5a5b5c5d);
 162 #ifdef TEST_U64
 163         test_illegal(u64, 0x5a5b5c5d6a6b6c6d);
 164 #endif
 165 #undef test_illegal
 166
 167         vm_munmap(user_addr, PAGE_SIZE * 2);
 168         kfree(kmem);
 169
 170         if (ret == 0) {
 171                 pr_info("tests passed.\n");
 172                 return 0;
 173         }
 174
 175         return -EINVAL;
 176 }
 177
 178 module_init(test_user_copy_init);
 179
 180 static void __exit test_user_copy_exit(void)
 181 {
 182         pr_info("unloaded.\n");
 183 }
 184
 185 module_exit(test_user_copy_exit);
 186
 187 MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
 188 MODULE_LICENSE("GPL");