/* * Kernel module for testing copy_to/from_user infrastructure. * * Copyright 2013 Google Inc. All Rights Reserved * * Authors: * Kees Cook <keescook@chromium.org> * * This software is licensed under the terms of the GNU General Public * License version 2, as published by the Free Software Foundation, and * may be copied, distributed, and modified under those terms. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. */ #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("%s\n", msg); \ cond; \ }) 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 /* * 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");