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1#include <linux/module.h>
2#include <linux/uaccess.h>
3#include <linux/kernel.h>
4#include <linux/errno.h>
5
6#include <asm/byteorder.h>
7#include <asm/word-at-a-time.h>
8
9#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
10#define IS_UNALIGNED(src, dst) 0
11#else
12#define IS_UNALIGNED(src, dst) \
13 (((long) dst | (long) src) & (sizeof(long) - 1))
14#endif
15
16/*
17 * Do a strncpy, return length of string without final '\0'.
18 * 'count' is the user-supplied count (return 'count' if we
19 * hit it), 'max' is the address space maximum (and we return
20 * -EFAULT if we hit it).
21 */
22static inline long do_strncpy_from_user(char *dst, const char __user *src, long count, unsigned long max)
23{
24 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
25 long res = 0;
26
27 /*
28 * Truncate 'max' to the user-specified limit, so that
29 * we only have one limit we need to check in the loop
30 */
31 if (max > count)
32 max = count;
33
34 if (IS_UNALIGNED(src, dst))
35 goto byte_at_a_time;
36
37 while (max >= sizeof(unsigned long)) {
38 unsigned long c, data;
39
40 /* Fall back to byte-at-a-time if we get a page fault */
41 if (unlikely(__get_user(c,(unsigned long __user *)(src+res))))
42 break;
43 *(unsigned long *)(dst+res) = c;
44 if (has_zero(c, &data, &constants)) {
45 data = prep_zero_mask(c, data, &constants);
46 data = create_zero_mask(data);
47 return res + find_zero(data);
48 }
49 res += sizeof(unsigned long);
50 max -= sizeof(unsigned long);
51 }
52
53byte_at_a_time:
54 while (max) {
55 char c;
56
57 if (unlikely(__get_user(c,src+res)))
58 return -EFAULT;
59 dst[res] = c;
60 if (!c)
61 return res;
62 res++;
63 max--;
64 }
65
66 /*
67 * Uhhuh. We hit 'max'. But was that the user-specified maximum
68 * too? If so, that's ok - we got as much as the user asked for.
69 */
70 if (res >= count)
71 return res;
72
73 /*
74 * Nope: we hit the address space limit, and we still had more
75 * characters the caller would have wanted. That's an EFAULT.
76 */
77 return -EFAULT;
78}
79
80/**
81 * strncpy_from_user: - Copy a NUL terminated string from userspace.
82 * @dst: Destination address, in kernel space. This buffer must be at
83 * least @count bytes long.
84 * @src: Source address, in user space.
85 * @count: Maximum number of bytes to copy, including the trailing NUL.
86 *
87 * Copies a NUL-terminated string from userspace to kernel space.
88 *
89 * On success, returns the length of the string (not including the trailing
90 * NUL).
91 *
92 * If access to userspace fails, returns -EFAULT (some data may have been
93 * copied).
94 *
95 * If @count is smaller than the length of the string, copies @count bytes
96 * and returns @count.
97 */
98long strncpy_from_user(char *dst, const char __user *src, long count)
99{
100 unsigned long max_addr, src_addr;
101
102 if (unlikely(count <= 0))
103 return 0;
104
105 max_addr = user_addr_max();
106 src_addr = (unsigned long)src;
107 if (likely(src_addr < max_addr)) {
108 unsigned long max = max_addr - src_addr;
109 return do_strncpy_from_user(dst, src, count, max);
110 }
111 return -EFAULT;
112}
113EXPORT_SYMBOL(strncpy_from_user);
1// SPDX-License-Identifier: GPL-2.0
2#include <linux/compiler.h>
3#include <linux/export.h>
4#include <linux/kasan-checks.h>
5#include <linux/thread_info.h>
6#include <linux/uaccess.h>
7#include <linux/kernel.h>
8#include <linux/errno.h>
9
10#include <asm/byteorder.h>
11#include <asm/word-at-a-time.h>
12
13#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
14#define IS_UNALIGNED(src, dst) 0
15#else
16#define IS_UNALIGNED(src, dst) \
17 (((long) dst | (long) src) & (sizeof(long) - 1))
18#endif
19
20/*
21 * Do a strncpy, return length of string without final '\0'.
22 * 'count' is the user-supplied count (return 'count' if we
23 * hit it), 'max' is the address space maximum (and we return
24 * -EFAULT if we hit it).
25 */
26static inline long do_strncpy_from_user(char *dst, const char __user *src, long count, unsigned long max)
27{
28 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
29 long res = 0;
30
31 /*
32 * Truncate 'max' to the user-specified limit, so that
33 * we only have one limit we need to check in the loop
34 */
35 if (max > count)
36 max = count;
37
38 if (IS_UNALIGNED(src, dst))
39 goto byte_at_a_time;
40
41 while (max >= sizeof(unsigned long)) {
42 unsigned long c, data;
43
44 /* Fall back to byte-at-a-time if we get a page fault */
45 unsafe_get_user(c, (unsigned long __user *)(src+res), byte_at_a_time);
46
47 *(unsigned long *)(dst+res) = c;
48 if (has_zero(c, &data, &constants)) {
49 data = prep_zero_mask(c, data, &constants);
50 data = create_zero_mask(data);
51 return res + find_zero(data);
52 }
53 res += sizeof(unsigned long);
54 max -= sizeof(unsigned long);
55 }
56
57byte_at_a_time:
58 while (max) {
59 char c;
60
61 unsafe_get_user(c,src+res, efault);
62 dst[res] = c;
63 if (!c)
64 return res;
65 res++;
66 max--;
67 }
68
69 /*
70 * Uhhuh. We hit 'max'. But was that the user-specified maximum
71 * too? If so, that's ok - we got as much as the user asked for.
72 */
73 if (res >= count)
74 return res;
75
76 /*
77 * Nope: we hit the address space limit, and we still had more
78 * characters the caller would have wanted. That's an EFAULT.
79 */
80efault:
81 return -EFAULT;
82}
83
84/**
85 * strncpy_from_user: - Copy a NUL terminated string from userspace.
86 * @dst: Destination address, in kernel space. This buffer must be at
87 * least @count bytes long.
88 * @src: Source address, in user space.
89 * @count: Maximum number of bytes to copy, including the trailing NUL.
90 *
91 * Copies a NUL-terminated string from userspace to kernel space.
92 *
93 * On success, returns the length of the string (not including the trailing
94 * NUL).
95 *
96 * If access to userspace fails, returns -EFAULT (some data may have been
97 * copied).
98 *
99 * If @count is smaller than the length of the string, copies @count bytes
100 * and returns @count.
101 */
102long strncpy_from_user(char *dst, const char __user *src, long count)
103{
104 unsigned long max_addr, src_addr;
105
106 if (unlikely(count <= 0))
107 return 0;
108
109 max_addr = user_addr_max();
110 src_addr = (unsigned long)src;
111 if (likely(src_addr < max_addr)) {
112 unsigned long max = max_addr - src_addr;
113 long retval;
114
115 kasan_check_write(dst, count);
116 check_object_size(dst, count, false);
117 user_access_begin();
118 retval = do_strncpy_from_user(dst, src, count, max);
119 user_access_end();
120 return retval;
121 }
122 return -EFAULT;
123}
124EXPORT_SYMBOL(strncpy_from_user);