// SPDX-License-Identifier: GPL-2.0-only
/*
* Kernel module for testing copy_to/from_user infrastructure.
*
* Copyright 2013 Google Inc. All Rights Reserved
*
* Authors:
* Kees Cook <keescook@chromium.org>
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/mman.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/vmalloc.h>
/*
* Several 32-bit architectures support 64-bit {get,put}_user() calls.
* As there doesn't appear to be anything that can safely determine
* their capability at compile-time, we just have to opt-out certain archs.
*/
#if BITS_PER_LONG == 64 || (!(defined(CONFIG_ARM) && !defined(MMU)) && \
!defined(CONFIG_M68K) && \
!defined(CONFIG_MICROBLAZE) && \
!defined(CONFIG_NIOS2) && \
!defined(CONFIG_PPC32) && \
!defined(CONFIG_SUPERH))
# define TEST_U64
#endif
#define test(condition, msg, ...) \
({ \
int cond = (condition); \
if (cond) \
pr_warn("[%d] " msg "\n", __LINE__, ##__VA_ARGS__); \
cond; \
})
static bool is_zeroed(void *from, size_t size)
{
return memchr_inv(from, 0x0, size) == NULL;
}
static int test_check_nonzero_user(char *kmem, char __user *umem, size_t size)
{
int ret = 0;
size_t start, end, i, zero_start, zero_end;
if (test(size < 2 * PAGE_SIZE, "buffer too small"))
return -EINVAL;
/*
* We want to cross a page boundary to exercise the code more
* effectively. We also don't want to make the size we scan too large,
* otherwise the test can take a long time and cause soft lockups. So
* scan a 1024 byte region across the page boundary.
*/
size = 1024;
start = PAGE_SIZE - (size / 2);
kmem += start;
umem += start;
zero_start = size / 4;
zero_end = size - zero_start;
/*
* We conduct a series of check_nonzero_user() tests on a block of
* memory with the following byte-pattern (trying every possible
* [start,end] pair):
*
* [ 00 ff 00 ff ... 00 00 00 00 ... ff 00 ff 00 ]
*
* And we verify that check_nonzero_user() acts identically to
* memchr_inv().
*/
memset(kmem, 0x0, size);
for (i = 1; i < zero_start; i += 2)
kmem[i] = 0xff;
for (i = zero_end; i < size; i += 2)
kmem[i] = 0xff;
ret |= test(copy_to_user(umem, kmem, size),
"legitimate copy_to_user failed");
for (start = 0; start <= size; start++) {
for (end = start; end <= size; end++) {
size_t len = end - start;
int retval = check_zeroed_user(umem + start, len);
int expected = is_zeroed(kmem + start, len);
ret |= test(retval != expected,
"check_nonzero_user(=%d) != memchr_inv(=%d) mismatch (start=%zu, end=%zu)",
retval, expected, start, end);
}
}
return ret;
}
static int test_copy_struct_from_user(char *kmem, char __user *umem,
size_t size)
{
int ret = 0;
char *umem_src = NULL, *expected = NULL;
size_t ksize, usize;
umem_src = kmalloc(size, GFP_KERNEL);
ret = test(umem_src == NULL, "kmalloc failed");
if (ret)
goto out_free;
expected = kmalloc(size, GFP_KERNEL);
ret = test(expected == NULL, "kmalloc failed");
if (ret)
goto out_free;
/* Fill umem with a fixed byte pattern. */
memset(umem_src, 0x3e, size);
ret |= test(copy_to_user(umem, umem_src, size),
"legitimate copy_to_user failed");
/* Check basic case -- (usize == ksize). */
ksize = size;
usize = size;
memcpy(expected, umem_src, ksize);
memset(kmem, 0x0, size);
ret |= test(copy_struct_from_user(kmem, ksize, umem, usize),
"copy_struct_from_user(usize == ksize) failed");
ret |= test(memcmp(kmem, expected, ksize),
"copy_struct_from_user(usize == ksize) gives unexpected copy");
/* Old userspace case -- (usize < ksize). */
ksize = size;
usize = size / 2;
memcpy(expected, umem_src, usize);
memset(expected + usize, 0x0, ksize - usize);
memset(kmem, 0x0, size);
ret |= test(copy_struct_from_user(kmem, ksize, umem, usize),
"copy_struct_from_user(usize < ksize) failed");
ret |= test(memcmp(kmem, expected, ksize),
"copy_struct_from_user(usize < ksize) gives unexpected copy");
/* New userspace (-E2BIG) case -- (usize > ksize). */
ksize = size / 2;
usize = size;
memset(kmem, 0x0, size);
ret |= test(copy_struct_from_user(kmem, ksize, umem, usize) != -E2BIG,
"copy_struct_from_user(usize > ksize) didn't give E2BIG");
/* New userspace (success) case -- (usize > ksize). */
ksize = size / 2;
usize = size;
memcpy(expected, umem_src, ksize);
ret |= test(clear_user(umem + ksize, usize - ksize),
"legitimate clear_user failed");
memset(kmem, 0x0, size);
ret |= test(copy_struct_from_user(kmem, ksize, umem, usize),
"copy_struct_from_user(usize > ksize) failed");
ret |= test(memcmp(kmem, expected, ksize),
"copy_struct_from_user(usize > ksize) gives unexpected copy");
out_free:
kfree(expected);
kfree(umem_src);
return ret;
}
static int __init test_user_copy_init(void)
{
int ret = 0;
char *kmem;
char __user *usermem;
char *bad_usermem;
unsigned long user_addr;
u8 val_u8;
u16 val_u16;
u32 val_u32;
#ifdef TEST_U64
u64 val_u64;
#endif
kmem = kmalloc(PAGE_SIZE * 2, GFP_KERNEL);
if (!kmem)
return -ENOMEM;
user_addr = vm_mmap(NULL, 0, PAGE_SIZE * 2,
PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_ANONYMOUS | MAP_PRIVATE, 0);
if (user_addr >= (unsigned long)(TASK_SIZE)) {
pr_warn("Failed to allocate user memory\n");
kfree(kmem);
return -ENOMEM;
}
usermem = (char __user *)user_addr;
bad_usermem = (char *)user_addr;
/*
* Legitimate usage: none of these copies should fail.
*/
memset(kmem, 0x3a, PAGE_SIZE * 2);
ret |= test(copy_to_user(usermem, kmem, PAGE_SIZE),
"legitimate copy_to_user failed");
memset(kmem, 0x0, PAGE_SIZE);
ret |= test(copy_from_user(kmem, usermem, PAGE_SIZE),
"legitimate copy_from_user failed");
ret |= test(memcmp(kmem, kmem + PAGE_SIZE, PAGE_SIZE),
"legitimate usercopy failed to copy data");
#define test_legit(size, check) \
do { \
val_##size = check; \
ret |= test(put_user(val_##size, (size __user *)usermem), \
"legitimate put_user (" #size ") failed"); \
val_##size = 0; \
ret |= test(get_user(val_##size, (size __user *)usermem), \
"legitimate get_user (" #size ") failed"); \
ret |= test(val_##size != check, \
"legitimate get_user (" #size ") failed to do copy"); \
if (val_##size != check) { \
pr_info("0x%llx != 0x%llx\n", \
(unsigned long long)val_##size, \
(unsigned long long)check); \
} \
} while (0)
test_legit(u8, 0x5a);
test_legit(u16, 0x5a5b);
test_legit(u32, 0x5a5b5c5d);
#ifdef TEST_U64
test_legit(u64, 0x5a5b5c5d6a6b6c6d);
#endif
#undef test_legit
/* Test usage of check_nonzero_user(). */
ret |= test_check_nonzero_user(kmem, usermem, 2 * PAGE_SIZE);
/* Test usage of copy_struct_from_user(). */
ret |= test_copy_struct_from_user(kmem, usermem, 2 * PAGE_SIZE);
/*
* Invalid usage: none of these copies should succeed.
*/
/* Prepare kernel memory with check values. */
memset(kmem, 0x5a, PAGE_SIZE);
memset(kmem + PAGE_SIZE, 0, PAGE_SIZE);
/* Reject kernel-to-kernel copies through copy_from_user(). */
ret |= test(!copy_from_user(kmem, (char __user *)(kmem + PAGE_SIZE),
PAGE_SIZE),
"illegal all-kernel copy_from_user passed");
/* Destination half of buffer should have been zeroed. */
ret |= test(memcmp(kmem + PAGE_SIZE, kmem, PAGE_SIZE),
"zeroing failure for illegal all-kernel copy_from_user");
#if 0
/*
* When running with SMAP/PAN/etc, this will Oops the kernel
* due to the zeroing of userspace memory on failure. This needs
* to be tested in LKDTM instead, since this test module does not
* expect to explode.
*/
ret |= test(!copy_from_user(bad_usermem, (char __user *)kmem,
PAGE_SIZE),
"illegal reversed copy_from_user passed");
#endif
ret |= test(!copy_to_user((char __user *)kmem, kmem + PAGE_SIZE,
PAGE_SIZE),
"illegal all-kernel copy_to_user passed");
ret |= test(!copy_to_user((char __user *)kmem, bad_usermem,
PAGE_SIZE),
"illegal reversed copy_to_user passed");
#define test_illegal(size, check) \
do { \
val_##size = (check); \
ret |= test(!get_user(val_##size, (size __user *)kmem), \
"illegal get_user (" #size ") passed"); \
ret |= test(val_##size != (size)0, \
"zeroing failure for illegal get_user (" #size ")"); \
if (val_##size != (size)0) { \
pr_info("0x%llx != 0\n", \
(unsigned long long)val_##size); \
} \
ret |= test(!put_user(val_##size, (size __user *)kmem), \
"illegal put_user (" #size ") passed"); \
} while (0)
test_illegal(u8, 0x5a);
test_illegal(u16, 0x5a5b);
test_illegal(u32, 0x5a5b5c5d);
#ifdef TEST_U64
test_illegal(u64, 0x5a5b5c5d6a6b6c6d);
#endif
#undef test_illegal
vm_munmap(user_addr, PAGE_SIZE * 2);
kfree(kmem);
if (ret == 0) {
pr_info("tests passed.\n");
return 0;
}
return -EINVAL;
}
module_init(test_user_copy_init);
static void __exit test_user_copy_exit(void)
{
pr_info("unloaded.\n");
}
module_exit(test_user_copy_exit);
MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
MODULE_LICENSE("GPL");
