/*
   * 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
  ", 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
  ");
  		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
  ",			  \
  				(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
  ",			    \
  				(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.
  ");
  		return 0;
  	}
  
  	return -EINVAL;
  }
  
  module_init(test_user_copy_init);
  
  static void __exit test_user_copy_exit(void)
  {
  	pr_info("unloaded.
  ");
  }
  
  module_exit(test_user_copy_exit);
  
  MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
  MODULE_LICENSE("GPL");