1/*
  2 * Access kernel memory without faulting.
  3 */
  4#include <linux/export.h>
  5#include <linux/mm.h>
  6#include <linux/uaccess.h>
  7
  8/**
  9 * probe_kernel_read(): safely attempt to read from a location
 10 * @dst: pointer to the buffer that shall take the data
 11 * @src: address to read from
 12 * @size: size of the data chunk
 13 *
 14 * Safely read from address @src to the buffer at @dst.  If a kernel fault
 15 * happens, handle that and return -EFAULT.
 16 *
 17 * We ensure that the copy_from_user is executed in atomic context so that
 18 * do_page_fault() doesn't attempt to take mmap_sem.  This makes
 19 * probe_kernel_read() suitable for use within regions where the caller
 20 * already holds mmap_sem, or other locks which nest inside mmap_sem.
 21 */
 22
 23long __weak probe_kernel_read(void *dst, const void *src, size_t size)
 24    __attribute__((alias("__probe_kernel_read")));
 25
 26long __probe_kernel_read(void *dst, const void *src, size_t size)
 27{
 28	long ret;
 29	mm_segment_t old_fs = get_fs();
 30
 31	set_fs(KERNEL_DS);
 32	pagefault_disable();
 33	ret = __copy_from_user_inatomic(dst,
 34			(__force const void __user *)src, size);
 35	pagefault_enable();
 36	set_fs(old_fs);
 37
 38	return ret ? -EFAULT : 0;
 39}
 40EXPORT_SYMBOL_GPL(probe_kernel_read);
 41
 42/**
 43 * probe_kernel_write(): safely attempt to write to a location
 44 * @dst: address to write to
 45 * @src: pointer to the data that shall be written
 46 * @size: size of the data chunk
 47 *
 48 * Safely write to address @dst from the buffer at @src.  If a kernel fault
 49 * happens, handle that and return -EFAULT.
 50 */
 51long __weak probe_kernel_write(void *dst, const void *src, size_t size)
 52    __attribute__((alias("__probe_kernel_write")));
 53
 54long __probe_kernel_write(void *dst, const void *src, size_t size)
 55{
 56	long ret;
 57	mm_segment_t old_fs = get_fs();
 58
 59	set_fs(KERNEL_DS);
 60	pagefault_disable();
 61	ret = __copy_to_user_inatomic((__force void __user *)dst, src, size);
 62	pagefault_enable();
 63	set_fs(old_fs);
 64
 65	return ret ? -EFAULT : 0;
 66}
 67EXPORT_SYMBOL_GPL(probe_kernel_write);
 68
 69/**
 70 * strncpy_from_unsafe: - Copy a NUL terminated string from unsafe address.
 71 * @dst:   Destination address, in kernel space.  This buffer must be at
 72 *         least @count bytes long.
 73 * @src:   Unsafe address.
 74 * @count: Maximum number of bytes to copy, including the trailing NUL.
 75 *
 76 * Copies a NUL-terminated string from unsafe address to kernel buffer.
 77 *
 78 * On success, returns the length of the string INCLUDING the trailing NUL.
 79 *
 80 * If access fails, returns -EFAULT (some data may have been copied
 81 * and the trailing NUL added).
 82 *
 83 * If @count is smaller than the length of the string, copies @count-1 bytes,
 84 * sets the last byte of @dst buffer to NUL and returns @count.
 85 */
 86long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count)
 87{
 88	mm_segment_t old_fs = get_fs();
 89	const void *src = unsafe_addr;
 90	long ret;
 91
 92	if (unlikely(count <= 0))
 93		return 0;
 94
 95	set_fs(KERNEL_DS);
 96	pagefault_disable();
 97
 98	do {
 99		ret = __copy_from_user_inatomic(dst++,
100						(const void __user __force *)src++, 1);
101	} while (dst[-1] && ret == 0 && src - unsafe_addr < count);
102
103	dst[-1] = '\0';
104	pagefault_enable();
105	set_fs(old_fs);
106
107	return ret ? -EFAULT : src - unsafe_addr;
108}

 1/*
 2 * Access kernel memory without faulting.
 3 */
 4#include <linux/module.h>
 5#include <linux/mm.h>
 6#include <linux/uaccess.h>
 7
 8/**
 9 * probe_kernel_read(): safely attempt to read from a location
10 * @dst: pointer to the buffer that shall take the data
11 * @src: address to read from
12 * @size: size of the data chunk
13 *
14 * Safely read from address @src to the buffer at @dst.  If a kernel fault
15 * happens, handle that and return -EFAULT.
 
 
 
 
 
16 */
17
18long __weak probe_kernel_read(void *dst, const void *src, size_t size)
19    __attribute__((alias("__probe_kernel_read")));
20
21long __probe_kernel_read(void *dst, const void *src, size_t size)
22{
23	long ret;
24	mm_segment_t old_fs = get_fs();
25
26	set_fs(KERNEL_DS);
27	pagefault_disable();
28	ret = __copy_from_user_inatomic(dst,
29			(__force const void __user *)src, size);
30	pagefault_enable();
31	set_fs(old_fs);
32
33	return ret ? -EFAULT : 0;
34}
35EXPORT_SYMBOL_GPL(probe_kernel_read);
36
37/**
38 * probe_kernel_write(): safely attempt to write to a location
39 * @dst: address to write to
40 * @src: pointer to the data that shall be written
41 * @size: size of the data chunk
42 *
43 * Safely write to address @dst from the buffer at @src.  If a kernel fault
44 * happens, handle that and return -EFAULT.
45 */
46long __weak probe_kernel_write(void *dst, const void *src, size_t size)
47    __attribute__((alias("__probe_kernel_write")));
48
49long __probe_kernel_write(void *dst, const void *src, size_t size)
50{
51	long ret;
52	mm_segment_t old_fs = get_fs();
53
54	set_fs(KERNEL_DS);
55	pagefault_disable();
56	ret = __copy_to_user_inatomic((__force void __user *)dst, src, size);
57	pagefault_enable();
58	set_fs(old_fs);
59
60	return ret ? -EFAULT : 0;
61}
62EXPORT_SYMBOL_GPL(probe_kernel_write);