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