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