/*
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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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* This software is licensed under the terms of the GNU General Public
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* License version 2, as published by the Free Software Foundation, and
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* may be copied, distributed, and modified under those terms.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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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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#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("%s\n", msg); \
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cond; \
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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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unsigned long value = 0x5A;
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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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ret |= test(copy_from_user(kmem, usermem, PAGE_SIZE),
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"legitimate copy_from_user failed");
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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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ret |= test(get_user(value, (unsigned long __user *)usermem),
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"legitimate get_user failed");
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ret |= test(put_user(value, (unsigned long __user *)usermem),
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"legitimate put_user failed");
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/*
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* Invalid usage: none of these copies should succeed.
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*/
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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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#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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ret |= test(!get_user(value, (unsigned long __user *)kmem),
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"illegal get_user passed");
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ret |= test(!put_user(value, (unsigned long __user *)kmem),
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"illegal put_user passed");
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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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