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("[%d] " msg "\n", __LINE__, ##__VA_ARGS__);     \
  39         cond;                                                           \
  40 })
  41
  42 static bool is_zeroed(void *from, size_t size)
  43 {
  44         return memchr_inv(from, 0x0, size) == NULL;
  45 }
  46
  47 static int test_check_nonzero_user(char *kmem, char __user *umem, size_t size)
  48 {
  49         int ret = 0;
  50         size_t start, end, i, zero_start, zero_end;
  51
  52         if (test(size < 2 * PAGE_SIZE, "buffer too small"))
  53                 return -EINVAL;
  54
  55         /*
  56          * We want to cross a page boundary to exercise the code more
  57          * effectively. We also don't want to make the size we scan too large,
  58          * otherwise the test can take a long time and cause soft lockups. So
  59          * scan a 1024 byte region across the page boundary.
  60          */
  61         size = 1024;
  62         start = PAGE_SIZE - (size / 2);
  63
  64         kmem += start;
  65         umem += start;
  66
  67         zero_start = size / 4;
  68         zero_end = size - zero_start;
  69
  70         /*
  71          * We conduct a series of check_nonzero_user() tests on a block of
  72          * memory with the following byte-pattern (trying every possible
  73          * [start,end] pair):
  74          *
  75          *   [ 00 ff 00 ff ... 00 00 00 00 ... ff 00 ff 00 ]
  76          *
  77          * And we verify that check_nonzero_user() acts identically to
  78          * memchr_inv().
  79          */
  80
  81         memset(kmem, 0x0, size);
  82         for (i = 1; i < zero_start; i += 2)
  83                 kmem[i] = 0xff;
  84         for (i = zero_end; i < size; i += 2)
  85                 kmem[i] = 0xff;
  86
  87         ret |= test(copy_to_user(umem, kmem, size),
  88                     "legitimate copy_to_user failed");
  89
  90         for (start = 0; start <= size; start++) {
  91                 for (end = start; end <= size; end++) {
  92                         size_t len = end - start;
  93                         int retval = check_zeroed_user(umem + start, len);
  94                         int expected = is_zeroed(kmem + start, len);
  95
  96                         ret |= test(retval != expected,
  97                                     "check_nonzero_user(=%d) != memchr_inv(=%d) mismatch (start=%zu, end=%zu)",
  98                                     retval, expected, start, end);
  99                 }
 100         }
 101
 102         return ret;
 103 }
 104
 105 static int test_copy_struct_from_user(char *kmem, char __user *umem,
 106                                       size_t size)
 107 {
 108         int ret = 0;
 109         char *umem_src = NULL, *expected = NULL;
 110         size_t ksize, usize;
 111
 112         umem_src = kmalloc(size, GFP_KERNEL);
 113         ret = test(umem_src == NULL, "kmalloc failed");
 114         if (ret)
 115                 goto out_free;
 116
 117         expected = kmalloc(size, GFP_KERNEL);
 118         ret = test(expected == NULL, "kmalloc failed");
 119         if (ret)
 120                 goto out_free;
 121
 122         /* Fill umem with a fixed byte pattern. */
 123         memset(umem_src, 0x3e, size);
 124         ret |= test(copy_to_user(umem, umem_src, size),
 125                     "legitimate copy_to_user failed");
 126
 127         /* Check basic case -- (usize == ksize). */
 128         ksize = size;
 129         usize = size;
 130
 131         memcpy(expected, umem_src, ksize);
 132
 133         memset(kmem, 0x0, size);
 134         ret |= test(copy_struct_from_user(kmem, ksize, umem, usize),
 135                     "copy_struct_from_user(usize == ksize) failed");
 136         ret |= test(memcmp(kmem, expected, ksize),
 137                     "copy_struct_from_user(usize == ksize) gives unexpected copy");
 138
 139         /* Old userspace case -- (usize < ksize). */
 140         ksize = size;
 141         usize = size / 2;
 142
 143         memcpy(expected, umem_src, usize);
 144         memset(expected + usize, 0x0, ksize - usize);
 145
 146         memset(kmem, 0x0, size);
 147         ret |= test(copy_struct_from_user(kmem, ksize, umem, usize),
 148                     "copy_struct_from_user(usize < ksize) failed");
 149         ret |= test(memcmp(kmem, expected, ksize),
 150                     "copy_struct_from_user(usize < ksize) gives unexpected copy");
 151
 152         /* New userspace (-E2BIG) case -- (usize > ksize). */
 153         ksize = size / 2;
 154         usize = size;
 155
 156         memset(kmem, 0x0, size);
 157         ret |= test(copy_struct_from_user(kmem, ksize, umem, usize) != -E2BIG,
 158                     "copy_struct_from_user(usize > ksize) didn't give E2BIG");
 159
 160         /* New userspace (success) case -- (usize > ksize). */
 161         ksize = size / 2;
 162         usize = size;
 163
 164         memcpy(expected, umem_src, ksize);
 165         ret |= test(clear_user(umem + ksize, usize - ksize),
 166                     "legitimate clear_user failed");
 167
 168         memset(kmem, 0x0, size);
 169         ret |= test(copy_struct_from_user(kmem, ksize, umem, usize),
 170                     "copy_struct_from_user(usize > ksize) failed");
 171         ret |= test(memcmp(kmem, expected, ksize),
 172                     "copy_struct_from_user(usize > ksize) gives unexpected copy");
 173
 174 out_free:
 175         kfree(expected);
 176         kfree(umem_src);
 177         return ret;
 178 }
 179
 180 static int __init test_user_copy_init(void)
 181 {
 182         int ret = 0;
 183         char *kmem;
 184         char __user *usermem;
 185         char *bad_usermem;
 186         unsigned long user_addr;
 187         u8 val_u8;
 188         u16 val_u16;
 189         u32 val_u32;
 190 #ifdef TEST_U64
 191         u64 val_u64;
 192 #endif
 193
 194         kmem = kmalloc(PAGE_SIZE * 2, GFP_KERNEL);
 195         if (!kmem)
 196                 return -ENOMEM;
 197
 198         user_addr = vm_mmap(NULL, 0, PAGE_SIZE * 2,
 199                             PROT_READ | PROT_WRITE | PROT_EXEC,
 200                             MAP_ANONYMOUS | MAP_PRIVATE, 0);
 201         if (user_addr >= (unsigned long)(TASK_SIZE)) {
 202                 pr_warn("Failed to allocate user memory\n");
 203                 kfree(kmem);
 204                 return -ENOMEM;
 205         }
 206
 207         usermem = (char __user *)user_addr;
 208         bad_usermem = (char *)user_addr;
 209
 210         /*
 211          * Legitimate usage: none of these copies should fail.
 212          */
 213         memset(kmem, 0x3a, PAGE_SIZE * 2);
 214         ret |= test(copy_to_user(usermem, kmem, PAGE_SIZE),
 215                     "legitimate copy_to_user failed");
 216         memset(kmem, 0x0, PAGE_SIZE);
 217         ret |= test(copy_from_user(kmem, usermem, PAGE_SIZE),
 218                     "legitimate copy_from_user failed");
 219         ret |= test(memcmp(kmem, kmem + PAGE_SIZE, PAGE_SIZE),
 220                     "legitimate usercopy failed to copy data");
 221
 222 #define test_legit(size, check)                                           \
 223         do {                                                              \
 224                 val_##size = check;                                       \
 225                 ret |= test(put_user(val_##size, (size __user *)usermem), \
 226                     "legitimate put_user (" #size ") failed");            \
 227                 val_##size = 0;                                           \
 228                 ret |= test(get_user(val_##size, (size __user *)usermem), \
 229                     "legitimate get_user (" #size ") failed");            \
 230                 ret |= test(val_##size != check,                          \
 231                     "legitimate get_user (" #size ") failed to do copy"); \
 232                 if (val_##size != check) {                                \
 233                         pr_info("0x%llx != 0x%llx\n",                     \
 234                                 (unsigned long long)val_##size,           \
 235                                 (unsigned long long)check);               \
 236                 }                                                         \
 237         } while (0)
 238
 239         test_legit(u8,  0x5a);
 240         test_legit(u16, 0x5a5b);
 241         test_legit(u32, 0x5a5b5c5d);
 242 #ifdef TEST_U64
 243         test_legit(u64, 0x5a5b5c5d6a6b6c6d);
 244 #endif
 245 #undef test_legit
 246
 247         /* Test usage of check_nonzero_user(). */
 248         ret |= test_check_nonzero_user(kmem, usermem, 2 * PAGE_SIZE);
 249         /* Test usage of copy_struct_from_user(). */
 250         ret |= test_copy_struct_from_user(kmem, usermem, 2 * PAGE_SIZE);
 251
 252         /*
 253          * Invalid usage: none of these copies should succeed.
 254          */
 255
 256         /* Prepare kernel memory with check values. */
 257         memset(kmem, 0x5a, PAGE_SIZE);
 258         memset(kmem + PAGE_SIZE, 0, PAGE_SIZE);
 259
 260         /* Reject kernel-to-kernel copies through copy_from_user(). */
 261         ret |= test(!copy_from_user(kmem, (char __user *)(kmem + PAGE_SIZE),
 262                                     PAGE_SIZE),
 263                     "illegal all-kernel copy_from_user passed");
 264
 265         /* Destination half of buffer should have been zeroed. */
 266         ret |= test(memcmp(kmem + PAGE_SIZE, kmem, PAGE_SIZE),
 267                     "zeroing failure for illegal all-kernel copy_from_user");
 268
 269 #if 0
 270         /*
 271          * When running with SMAP/PAN/etc, this will Oops the kernel
 272          * due to the zeroing of userspace memory on failure. This needs
 273          * to be tested in LKDTM instead, since this test module does not
 274          * expect to explode.
 275          */
 276         ret |= test(!copy_from_user(bad_usermem, (char __user *)kmem,
 277                                     PAGE_SIZE),
 278                     "illegal reversed copy_from_user passed");
 279 #endif
 280         ret |= test(!copy_to_user((char __user *)kmem, kmem + PAGE_SIZE,
 281                                   PAGE_SIZE),
 282                     "illegal all-kernel copy_to_user passed");
 283         ret |= test(!copy_to_user((char __user *)kmem, bad_usermem,
 284                                   PAGE_SIZE),
 285                     "illegal reversed copy_to_user passed");
 286
 287 #define test_illegal(size, check)                                           \
 288         do {                                                                \
 289                 val_##size = (check);                                       \
 290                 ret |= test(!get_user(val_##size, (size __user *)kmem),     \
 291                     "illegal get_user (" #size ") passed");                 \
 292                 ret |= test(val_##size != (size)0,                          \
 293                     "zeroing failure for illegal get_user (" #size ")");    \
 294                 if (val_##size != (size)0) {                                \
 295                         pr_info("0x%llx != 0\n",                            \
 296                                 (unsigned long long)val_##size);            \
 297                 }                                                           \
 298                 ret |= test(!put_user(val_##size, (size __user *)kmem),     \
 299                     "illegal put_user (" #size ") passed");                 \
 300         } while (0)
 301
 302         test_illegal(u8,  0x5a);
 303         test_illegal(u16, 0x5a5b);
 304         test_illegal(u32, 0x5a5b5c5d);
 305 #ifdef TEST_U64
 306         test_illegal(u64, 0x5a5b5c5d6a6b6c6d);
 307 #endif
 308 #undef test_illegal
 309
 310         vm_munmap(user_addr, PAGE_SIZE * 2);
 311         kfree(kmem);
 312
 313         if (ret == 0) {
 314                 pr_info("tests passed.\n");
 315                 return 0;
 316         }
 317
 318         return -EINVAL;
 319 }
 320
 321 module_init(test_user_copy_init);
 322
 323 static void __exit test_user_copy_exit(void)
 324 {
 325         pr_info("unloaded.\n");
 326 }
 327
 328 module_exit(test_user_copy_exit);
 329
 330 MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
 331 MODULE_LICENSE("GPL");