// 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 "
  ", __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
  ");
  		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

  	/* 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
  ",			    \
  				(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");