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