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