1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 * Copyright (c) 2020 Christoph Hellwig.
4 *
5 * Support for "universal" pointers that can point to either kernel or userspace
6 * memory.
7 */
8#ifndef _LINUX_SOCKPTR_H
9#define _LINUX_SOCKPTR_H
10
11#include <linux/slab.h>
12#include <linux/uaccess.h>
13
14typedef struct {
15 union {
16 void *kernel;
17 void __user *user;
18 };
19 bool is_kernel : 1;
20} sockptr_t;
21
22static inline bool sockptr_is_kernel(sockptr_t sockptr)
23{
24 return sockptr.is_kernel;
25}
26
27static inline sockptr_t KERNEL_SOCKPTR(void *p)
28{
29 return (sockptr_t) { .kernel = p, .is_kernel = true };
30}
31
32static inline sockptr_t USER_SOCKPTR(void __user *p)
33{
34 return (sockptr_t) { .user = p };
35}
36
37static inline bool sockptr_is_null(sockptr_t sockptr)
38{
39 if (sockptr_is_kernel(sockptr))
40 return !sockptr.kernel;
41 return !sockptr.user;
42}
43
44static inline int copy_from_sockptr_offset(void *dst, sockptr_t src,
45 size_t offset, size_t size)
46{
47 if (!sockptr_is_kernel(sockptr: src))
48 return copy_from_user(to: dst, from: src.user + offset, n: size);
49 memcpy(dst, src.kernel + offset, size);
50 return 0;
51}
52
53/* Deprecated.
54 * This is unsafe, unless caller checked user provided optlen.
55 * Prefer copy_safe_from_sockptr() instead.
56 */
57static inline int copy_from_sockptr(void *dst, sockptr_t src, size_t size)
58{
59 return copy_from_sockptr_offset(dst, src, offset: 0, size);
60}
61
62/**
63 * copy_safe_from_sockptr: copy a struct from sockptr
64 * @dst: Destination address, in kernel space. This buffer must be @ksize
65 * bytes long.
66 * @ksize: Size of @dst struct.
67 * @optval: Source address. (in user or kernel space)
68 * @optlen: Size of @optval data.
69 *
70 * Returns:
71 * * -EINVAL: @optlen < @ksize
72 * * -EFAULT: access to userspace failed.
73 * * 0 : @ksize bytes were copied
74 */
75static inline int copy_safe_from_sockptr(void *dst, size_t ksize,
76 sockptr_t optval, unsigned int optlen)
77{
78 if (optlen < ksize)
79 return -EINVAL;
80 return copy_from_sockptr(dst, src: optval, size: ksize);
81}
82
83static inline int copy_struct_from_sockptr(void *dst, size_t ksize,
84 sockptr_t src, size_t usize)
85{
86 size_t size = min(ksize, usize);
87 size_t rest = max(ksize, usize) - size;
88
89 if (!sockptr_is_kernel(sockptr: src))
90 return copy_struct_from_user(dst, ksize, src: src.user, usize: size);
91
92 if (usize < ksize) {
93 memset(dst + size, 0, rest);
94 } else if (usize > ksize) {
95 char *p = src.kernel;
96
97 while (rest--) {
98 if (*p++)
99 return -E2BIG;
100 }
101 }
102 memcpy(dst, src.kernel, size);
103 return 0;
104}
105
106static inline int copy_to_sockptr_offset(sockptr_t dst, size_t offset,
107 const void *src, size_t size)
108{
109 if (!sockptr_is_kernel(sockptr: dst))
110 return copy_to_user(to: dst.user + offset, from: src, n: size);
111 memcpy(dst.kernel + offset, src, size);
112 return 0;
113}
114
115static inline int copy_to_sockptr(sockptr_t dst, const void *src, size_t size)
116{
117 return copy_to_sockptr_offset(dst, offset: 0, src, size);
118}
119
120static inline void *memdup_sockptr(sockptr_t src, size_t len)
121{
122 void *p = kmalloc_track_caller(len, GFP_USER | __GFP_NOWARN);
123
124 if (!p)
125 return ERR_PTR(error: -ENOMEM);
126 if (copy_from_sockptr(dst: p, src, size: len)) {
127 kfree(objp: p);
128 return ERR_PTR(error: -EFAULT);
129 }
130 return p;
131}
132
133static inline void *memdup_sockptr_nul(sockptr_t src, size_t len)
134{
135 char *p = kmalloc_track_caller(len + 1, GFP_KERNEL);
136
137 if (!p)
138 return ERR_PTR(error: -ENOMEM);
139 if (copy_from_sockptr(dst: p, src, size: len)) {
140 kfree(objp: p);
141 return ERR_PTR(error: -EFAULT);
142 }
143 p[len] = '\0';
144 return p;
145}
146
147static inline long strncpy_from_sockptr(char *dst, sockptr_t src, size_t count)
148{
149 if (sockptr_is_kernel(sockptr: src)) {
150 size_t len = min(strnlen(src.kernel, count - 1) + 1, count);
151
152 memcpy(dst, src.kernel, len);
153 return len;
154 }
155 return strncpy_from_user(dst, src: src.user, count);
156}
157
158static inline int check_zeroed_sockptr(sockptr_t src, size_t offset,
159 size_t size)
160{
161 if (!sockptr_is_kernel(sockptr: src))
162 return check_zeroed_user(from: src.user + offset, size);
163 return memchr_inv(p: src.kernel + offset, c: 0, size) == NULL;
164}
165
166#endif /* _LINUX_SOCKPTR_H */
167

source code of linux/include/linux/sockptr.h