1// SPDX-License-Identifier: GPL-2.0
2#include <linux/bitops.h>
3#include <linux/fault-inject-usercopy.h>
4#include <linux/instrumented.h>
5#include <linux/uaccess.h>
6#include <linux/nospec.h>
7
8/* out-of-line parts */
9
10#ifndef INLINE_COPY_FROM_USER
11unsigned long _copy_from_user(void *to, const void __user *from, unsigned long n)
12{
13 unsigned long res = n;
14 might_fault();
15 if (!should_fail_usercopy() && likely(access_ok(from, n))) {
16 /*
17 * Ensure that bad access_ok() speculation will not
18 * lead to nasty side effects *after* the copy is
19 * finished:
20 */
21 barrier_nospec();
22 instrument_copy_from_user_before(to, from, n);
23 res = raw_copy_from_user(dst: to, src: from, size: n);
24 instrument_copy_from_user_after(to, from, n, left: res);
25 }
26 if (unlikely(res))
27 memset(to + (n - res), 0, res);
28 return res;
29}
30EXPORT_SYMBOL(_copy_from_user);
31#endif
32
33#ifndef INLINE_COPY_TO_USER
34unsigned long _copy_to_user(void __user *to, const void *from, unsigned long n)
35{
36 might_fault();
37 if (should_fail_usercopy())
38 return n;
39 if (likely(access_ok(to, n))) {
40 instrument_copy_to_user(to, from, n);
41 n = raw_copy_to_user(dst: to, src: from, size: n);
42 }
43 return n;
44}
45EXPORT_SYMBOL(_copy_to_user);
46#endif
47
48/**
49 * check_zeroed_user: check if a userspace buffer only contains zero bytes
50 * @from: Source address, in userspace.
51 * @size: Size of buffer.
52 *
53 * This is effectively shorthand for "memchr_inv(from, 0, size) == NULL" for
54 * userspace addresses (and is more efficient because we don't care where the
55 * first non-zero byte is).
56 *
57 * Returns:
58 * * 0: There were non-zero bytes present in the buffer.
59 * * 1: The buffer was full of zero bytes.
60 * * -EFAULT: access to userspace failed.
61 */
62int check_zeroed_user(const void __user *from, size_t size)
63{
64 unsigned long val;
65 uintptr_t align = (uintptr_t) from % sizeof(unsigned long);
66
67 if (unlikely(size == 0))
68 return 1;
69
70 from -= align;
71 size += align;
72
73 if (!user_read_access_begin(from, size))
74 return -EFAULT;
75
76 unsafe_get_user(val, (unsigned long __user *) from, err_fault);
77 if (align)
78 val &= ~aligned_byte_mask(align);
79
80 while (size > sizeof(unsigned long)) {
81 if (unlikely(val))
82 goto done;
83
84 from += sizeof(unsigned long);
85 size -= sizeof(unsigned long);
86
87 unsafe_get_user(val, (unsigned long __user *) from, err_fault);
88 }
89
90 if (size < sizeof(unsigned long))
91 val &= aligned_byte_mask(size);
92
93done:
94 user_read_access_end();
95 return (val == 0);
96err_fault:
97 user_read_access_end();
98 return -EFAULT;
99}
100EXPORT_SYMBOL(check_zeroed_user);
101

source code of linux/lib/usercopy.c