// 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");