the-tree/lib/test_user_copy.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  * Kernel module for testing copy_to/from_user infrastructure.
0004  *
0005  * Copyright 2013 Google Inc. All Rights Reserved
0006  *
0007  * Authors:
0008  *      Kees Cook       <keescook@chromium.org>
0009  */
0010
0011 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
0012
0013 #include <linux/mman.h>
0014 #include <linux/module.h>
0015 #include <linux/sched.h>
0016 #include <linux/slab.h>
0017 #include <linux/uaccess.h>
0018 #include <linux/vmalloc.h>
0019
0020 /*
0021  * Several 32-bit architectures support 64-bit {get,put}_user() calls.
0022  * As there doesn't appear to be anything that can safely determine
0023  * their capability at compile-time, we just have to opt-out certain archs.
0024  */
0025 #if BITS_PER_LONG == 64 || (!(defined(CONFIG_ARM) && !defined(MMU)) && \
0026                 !defined(CONFIG_M68K) &&        \
0027                 !defined(CONFIG_MICROBLAZE) &&  \
0028                 !defined(CONFIG_NIOS2) &&       \
0029                 !defined(CONFIG_PPC32) &&       \
0030                 !defined(CONFIG_SUPERH))
0031 # define TEST_U64
0032 #endif
0033
0034 #define test(condition, msg, ...)                   \
0035 ({                                  \
0036     int cond = (condition);                     \
0037     if (cond)                           \
0038         pr_warn("[%d] " msg "\n", __LINE__, ##__VA_ARGS__); \
0039     cond;                               \
0040 })
0041
0042 static bool is_zeroed(void *from, size_t size)
0043 {
0044     return memchr_inv(from, 0x0, size) == NULL;
0045 }
0046
0047 static int test_check_nonzero_user(char *kmem, char __user *umem, size_t size)
0048 {
0049     int ret = 0;
0050     size_t start, end, i, zero_start, zero_end;
0051
0052     if (test(size < 2 * PAGE_SIZE, "buffer too small"))
0053         return -EINVAL;
0054
0055     /*
0056      * We want to cross a page boundary to exercise the code more
0057      * effectively. We also don't want to make the size we scan too large,
0058      * otherwise the test can take a long time and cause soft lockups. So
0059      * scan a 1024 byte region across the page boundary.
0060      */
0061     size = 1024;
0062     start = PAGE_SIZE - (size / 2);
0063
0064     kmem += start;
0065     umem += start;
0066
0067     zero_start = size / 4;
0068     zero_end = size - zero_start;
0069
0070     /*
0071      * We conduct a series of check_nonzero_user() tests on a block of
0072      * memory with the following byte-pattern (trying every possible
0073      * [start,end] pair):
0074      *
0075      *   [ 00 ff 00 ff ... 00 00 00 00 ... ff 00 ff 00 ]
0076      *
0077      * And we verify that check_nonzero_user() acts identically to
0078      * memchr_inv().
0079      */
0080
0081     memset(kmem, 0x0, size);
0082     for (i = 1; i < zero_start; i += 2)
0083         kmem[i] = 0xff;
0084     for (i = zero_end; i < size; i += 2)
0085         kmem[i] = 0xff;
0086
0087     ret |= test(copy_to_user(umem, kmem, size),
0088             "legitimate copy_to_user failed");
0089
0090     for (start = 0; start <= size; start++) {
0091         for (end = start; end <= size; end++) {
0092             size_t len = end - start;
0093             int retval = check_zeroed_user(umem + start, len);
0094             int expected = is_zeroed(kmem + start, len);
0095
0096             ret |= test(retval != expected,
0097                     "check_nonzero_user(=%d) != memchr_inv(=%d) mismatch (start=%zu, end=%zu)",
0098                     retval, expected, start, end);
0099         }
0100     }
0101
0102     return ret;
0103 }
0104
0105 static int test_copy_struct_from_user(char *kmem, char __user *umem,
0106                       size_t size)
0107 {
0108     int ret = 0;
0109     char *umem_src = NULL, *expected = NULL;
0110     size_t ksize, usize;
0111
0112     umem_src = kmalloc(size, GFP_KERNEL);
0113     ret = test(umem_src == NULL, "kmalloc failed");
0114     if (ret)
0115         goto out_free;
0116
0117     expected = kmalloc(size, GFP_KERNEL);
0118     ret = test(expected == NULL, "kmalloc failed");
0119     if (ret)
0120         goto out_free;
0121
0122     /* Fill umem with a fixed byte pattern. */
0123     memset(umem_src, 0x3e, size);
0124     ret |= test(copy_to_user(umem, umem_src, size),
0125             "legitimate copy_to_user failed");
0126
0127     /* Check basic case -- (usize == ksize). */
0128     ksize = size;
0129     usize = size;
0130
0131     memcpy(expected, umem_src, ksize);
0132
0133     memset(kmem, 0x0, size);
0134     ret |= test(copy_struct_from_user(kmem, ksize, umem, usize),
0135             "copy_struct_from_user(usize == ksize) failed");
0136     ret |= test(memcmp(kmem, expected, ksize),
0137             "copy_struct_from_user(usize == ksize) gives unexpected copy");
0138
0139     /* Old userspace case -- (usize < ksize). */
0140     ksize = size;
0141     usize = size / 2;
0142
0143     memcpy(expected, umem_src, usize);
0144     memset(expected + usize, 0x0, ksize - usize);
0145
0146     memset(kmem, 0x0, size);
0147     ret |= test(copy_struct_from_user(kmem, ksize, umem, usize),
0148             "copy_struct_from_user(usize < ksize) failed");
0149     ret |= test(memcmp(kmem, expected, ksize),
0150             "copy_struct_from_user(usize < ksize) gives unexpected copy");
0151
0152     /* New userspace (-E2BIG) case -- (usize > ksize). */
0153     ksize = size / 2;
0154     usize = size;
0155
0156     memset(kmem, 0x0, size);
0157     ret |= test(copy_struct_from_user(kmem, ksize, umem, usize) != -E2BIG,
0158             "copy_struct_from_user(usize > ksize) didn't give E2BIG");
0159
0160     /* New userspace (success) case -- (usize > ksize). */
0161     ksize = size / 2;
0162     usize = size;
0163
0164     memcpy(expected, umem_src, ksize);
0165     ret |= test(clear_user(umem + ksize, usize - ksize),
0166             "legitimate clear_user failed");
0167
0168     memset(kmem, 0x0, size);
0169     ret |= test(copy_struct_from_user(kmem, ksize, umem, usize),
0170             "copy_struct_from_user(usize > ksize) failed");
0171     ret |= test(memcmp(kmem, expected, ksize),
0172             "copy_struct_from_user(usize > ksize) gives unexpected copy");
0173
0174 out_free:
0175     kfree(expected);
0176     kfree(umem_src);
0177     return ret;
0178 }
0179
0180 static int __init test_user_copy_init(void)
0181 {
0182     int ret = 0;
0183     char *kmem;
0184     char __user *usermem;
0185     char *bad_usermem;
0186     unsigned long user_addr;
0187     u8 val_u8;
0188     u16 val_u16;
0189     u32 val_u32;
0190 #ifdef TEST_U64
0191     u64 val_u64;
0192 #endif
0193
0194     kmem = kmalloc(PAGE_SIZE * 2, GFP_KERNEL);
0195     if (!kmem)
0196         return -ENOMEM;
0197
0198     user_addr = vm_mmap(NULL, 0, PAGE_SIZE * 2,
0199                 PROT_READ | PROT_WRITE | PROT_EXEC,
0200                 MAP_ANONYMOUS | MAP_PRIVATE, 0);
0201     if (user_addr >= (unsigned long)(TASK_SIZE)) {
0202         pr_warn("Failed to allocate user memory\n");
0203         kfree(kmem);
0204         return -ENOMEM;
0205     }
0206
0207     usermem = (char __user *)user_addr;
0208     bad_usermem = (char *)user_addr;
0209
0210     /*
0211      * Legitimate usage: none of these copies should fail.
0212      */
0213     memset(kmem, 0x3a, PAGE_SIZE * 2);
0214     ret |= test(copy_to_user(usermem, kmem, PAGE_SIZE),
0215             "legitimate copy_to_user failed");
0216     memset(kmem, 0x0, PAGE_SIZE);
0217     ret |= test(copy_from_user(kmem, usermem, PAGE_SIZE),
0218             "legitimate copy_from_user failed");
0219     ret |= test(memcmp(kmem, kmem + PAGE_SIZE, PAGE_SIZE),
0220             "legitimate usercopy failed to copy data");
0221
0222 #define test_legit(size, check)                       \
0223     do {                                  \
0224         val_##size = check;                   \
0225         ret |= test(put_user(val_##size, (size __user *)usermem), \
0226             "legitimate put_user (" #size ") failed");        \
0227         val_##size = 0;                       \
0228         ret |= test(get_user(val_##size, (size __user *)usermem), \
0229             "legitimate get_user (" #size ") failed");        \
0230         ret |= test(val_##size != check,              \
0231             "legitimate get_user (" #size ") failed to do copy"); \
0232         if (val_##size != check) {                \
0233             pr_info("0x%llx != 0x%llx\n",             \
0234                 (unsigned long long)val_##size,       \
0235                 (unsigned long long)check);       \
0236         }                             \
0237     } while (0)
0238
0239     test_legit(u8,  0x5a);
0240     test_legit(u16, 0x5a5b);
0241     test_legit(u32, 0x5a5b5c5d);
0242 #ifdef TEST_U64
0243     test_legit(u64, 0x5a5b5c5d6a6b6c6d);
0244 #endif
0245 #undef test_legit
0246
0247     /* Test usage of check_nonzero_user(). */
0248     ret |= test_check_nonzero_user(kmem, usermem, 2 * PAGE_SIZE);
0249     /* Test usage of copy_struct_from_user(). */
0250     ret |= test_copy_struct_from_user(kmem, usermem, 2 * PAGE_SIZE);
0251
0252     /*
0253      * Invalid usage: none of these copies should succeed.
0254      */
0255
0256     /* Prepare kernel memory with check values. */
0257     memset(kmem, 0x5a, PAGE_SIZE);
0258     memset(kmem + PAGE_SIZE, 0, PAGE_SIZE);
0259
0260     /* Reject kernel-to-kernel copies through copy_from_user(). */
0261     ret |= test(!copy_from_user(kmem, (char __user *)(kmem + PAGE_SIZE),
0262                     PAGE_SIZE),
0263             "illegal all-kernel copy_from_user passed");
0264
0265     /* Destination half of buffer should have been zeroed. */
0266     ret |= test(memcmp(kmem + PAGE_SIZE, kmem, PAGE_SIZE),
0267             "zeroing failure for illegal all-kernel copy_from_user");
0268
0269 #if 0
0270     /*
0271      * When running with SMAP/PAN/etc, this will Oops the kernel
0272      * due to the zeroing of userspace memory on failure. This needs
0273      * to be tested in LKDTM instead, since this test module does not
0274      * expect to explode.
0275      */
0276     ret |= test(!copy_from_user(bad_usermem, (char __user *)kmem,
0277                     PAGE_SIZE),
0278             "illegal reversed copy_from_user passed");
0279 #endif
0280     ret |= test(!copy_to_user((char __user *)kmem, kmem + PAGE_SIZE,
0281                   PAGE_SIZE),
0282             "illegal all-kernel copy_to_user passed");
0283     ret |= test(!copy_to_user((char __user *)kmem, bad_usermem,
0284                   PAGE_SIZE),
0285             "illegal reversed copy_to_user passed");
0286
0287 #define test_illegal(size, check)                       \
0288     do {                                    \
0289         val_##size = (check);                       \
0290         ret |= test(!get_user(val_##size, (size __user *)kmem),     \
0291             "illegal get_user (" #size ") passed");         \
0292         ret |= test(val_##size != (size)0,              \
0293             "zeroing failure for illegal get_user (" #size ")");    \
0294         if (val_##size != (size)0) {                    \
0295             pr_info("0x%llx != 0\n",                \
0296                 (unsigned long long)val_##size);        \
0297         }                               \
0298         ret |= test(!put_user(val_##size, (size __user *)kmem),     \
0299             "illegal put_user (" #size ") passed");         \
0300     } while (0)
0301
0302     test_illegal(u8,  0x5a);
0303     test_illegal(u16, 0x5a5b);
0304     test_illegal(u32, 0x5a5b5c5d);
0305 #ifdef TEST_U64
0306     test_illegal(u64, 0x5a5b5c5d6a6b6c6d);
0307 #endif
0308 #undef test_illegal
0309
0310     vm_munmap(user_addr, PAGE_SIZE * 2);
0311     kfree(kmem);
0312
0313     if (ret == 0) {
0314         pr_info("tests passed.\n");
0315         return 0;
0316     }
0317
0318     return -EINVAL;
0319 }
0320
0321 module_init(test_user_copy_init);
0322
0323 static void __exit test_user_copy_exit(void)
0324 {
0325     pr_info("unloaded.\n");
0326 }
0327
0328 module_exit(test_user_copy_exit);
0329
0330 MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
0331 MODULE_LICENSE("GPL");