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