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
_copy_from_user(void * to,const void __user * from,unsigned long n)11 unsigned 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(to, from, n);
24 		instrument_copy_from_user_after(to, from, n, res);
25 	}
26 	if (unlikely(res))
27 		memset(to + (n - res), 0, res);
28 	return res;
29 }
30 EXPORT_SYMBOL(_copy_from_user);
31 #endif
32 
33 #ifndef INLINE_COPY_TO_USER
_copy_to_user(void __user * to,const void * from,unsigned long n)34 unsigned 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(to, from, n);
42 	}
43 	return n;
44 }
45 EXPORT_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  */
check_zeroed_user(const void __user * from,size_t size)62 int 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 
93 done:
94 	user_read_access_end();
95 	return (val == 0);
96 err_fault:
97 	user_read_access_end();
98 	return -EFAULT;
99 }
100 EXPORT_SYMBOL(check_zeroed_user);
101