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