1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/compiler.h>
3 #include <linux/errno.h>
4 #include <linux/export.h>
5 #include <linux/fault-inject-usercopy.h>
6 #include <linux/instrumented.h>
7 #include <linux/kernel.h>
8 #include <linux/nospec.h>
9 #include <linux/string.h>
10 #include <linux/uaccess.h>
11 #include <linux/wordpart.h>
12
13 /* out-of-line parts */
14
15 #ifndef INLINE_COPY_FROM_USER
_copy_from_user(void * to,const void __user * from,unsigned long n)16 unsigned long _copy_from_user(void *to, const void __user *from, unsigned long n)
17 {
18 unsigned long res = n;
19 might_fault();
20 if (!should_fail_usercopy() && likely(access_ok(from, n))) {
21 /*
22 * Ensure that bad access_ok() speculation will not
23 * lead to nasty side effects *after* the copy is
24 * finished:
25 */
26 barrier_nospec();
27 instrument_copy_from_user_before(to, from, n);
28 res = raw_copy_from_user(to, from, n);
29 instrument_copy_from_user_after(to, from, n, res);
30 }
31 if (unlikely(res))
32 memset(to + (n - res), 0, res);
33 return res;
34 }
35 EXPORT_SYMBOL(_copy_from_user);
36 #endif
37
38 #ifndef INLINE_COPY_TO_USER
_copy_to_user(void __user * to,const void * from,unsigned long n)39 unsigned long _copy_to_user(void __user *to, const void *from, unsigned long n)
40 {
41 might_fault();
42 if (should_fail_usercopy())
43 return n;
44 if (likely(access_ok(to, n))) {
45 instrument_copy_to_user(to, from, n);
46 n = raw_copy_to_user(to, from, n);
47 }
48 return n;
49 }
50 EXPORT_SYMBOL(_copy_to_user);
51 #endif
52
53 /**
54 * check_zeroed_user: check if a userspace buffer only contains zero bytes
55 * @from: Source address, in userspace.
56 * @size: Size of buffer.
57 *
58 * This is effectively shorthand for "memchr_inv(from, 0, size) == NULL" for
59 * userspace addresses (and is more efficient because we don't care where the
60 * first non-zero byte is).
61 *
62 * Returns:
63 * * 0: There were non-zero bytes present in the buffer.
64 * * 1: The buffer was full of zero bytes.
65 * * -EFAULT: access to userspace failed.
66 */
check_zeroed_user(const void __user * from,size_t size)67 int check_zeroed_user(const void __user *from, size_t size)
68 {
69 unsigned long val;
70 uintptr_t align = (uintptr_t) from % sizeof(unsigned long);
71
72 if (unlikely(size == 0))
73 return 1;
74
75 from -= align;
76 size += align;
77
78 if (!user_read_access_begin(from, size))
79 return -EFAULT;
80
81 unsafe_get_user(val, (unsigned long __user *) from, err_fault);
82 if (align)
83 val &= ~aligned_byte_mask(align);
84
85 while (size > sizeof(unsigned long)) {
86 if (unlikely(val))
87 goto done;
88
89 from += sizeof(unsigned long);
90 size -= sizeof(unsigned long);
91
92 unsafe_get_user(val, (unsigned long __user *) from, err_fault);
93 }
94
95 if (size < sizeof(unsigned long))
96 val &= aligned_byte_mask(size);
97
98 done:
99 user_read_access_end();
100 return (val == 0);
101 err_fault:
102 user_read_access_end();
103 return -EFAULT;
104 }
105 EXPORT_SYMBOL(check_zeroed_user);
106