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 *
57 * Returns 0 for success, or number of bytes not copied on error.
58 */
59static inline int copy_from_sockptr(void *dst, sockptr_t src, size_t size)
60{
61 return copy_from_sockptr_offset(dst, src, offset: 0, size);
62}
63
64/**
65 * copy_safe_from_sockptr: copy a struct from sockptr
66 * @dst: Destination address, in kernel space. This buffer must be @ksize
67 * bytes long.
68 * @ksize: Size of @dst struct.
69 * @optval: Source address. (in user or kernel space)
70 * @optlen: Size of @optval data.
71 *
72 * Returns:
73 * * -EINVAL: @optlen < @ksize
74 * * -EFAULT: access to userspace failed.
75 * * 0 : @ksize bytes were copied
76 */
77static inline int copy_safe_from_sockptr(void *dst, size_t ksize,
78 sockptr_t optval, unsigned int optlen)
79{
80 if (optlen < ksize)
81 return -EINVAL;
82 if (copy_from_sockptr(dst, src: optval, size: ksize))
83 return -EFAULT;
84 return 0;
85}
86
87static inline int copy_struct_from_sockptr(void *dst, size_t ksize,
88 sockptr_t src, size_t usize)
89{
90 size_t size = min(ksize, usize);
91 size_t rest = max(ksize, usize) - size;
92
93 if (!sockptr_is_kernel(sockptr: src))
94 return copy_struct_from_user(dst, ksize, src: src.user, usize: size);
95
96 if (usize < ksize) {
97 memset(dst + size, 0, rest);
98 } else if (usize > ksize) {
99 char *p = src.kernel;
100
101 while (rest--) {
102 if (*p++)
103 return -E2BIG;
104 }
105 }
106 memcpy(dst, src.kernel, size);
107 return 0;
108}
109
110static inline int copy_to_sockptr_offset(sockptr_t dst, size_t offset,
111 const void *src, size_t size)
112{
113 if (!sockptr_is_kernel(sockptr: dst))
114 return copy_to_user(to: dst.user + offset, from: src, n: size);
115 memcpy(dst.kernel + offset, src, size);
116 return 0;
117}
118
119static inline int copy_to_sockptr(sockptr_t dst, const void *src, size_t size)
120{
121 return copy_to_sockptr_offset(dst, offset: 0, src, size);
122}
123
124static inline void *memdup_sockptr_noprof(sockptr_t src, size_t len)
125{
126 void *p = kmalloc_track_caller_noprof(len, GFP_USER | __GFP_NOWARN);
127
128 if (!p)
129 return ERR_PTR(error: -ENOMEM);
130 if (copy_from_sockptr(dst: p, src, size: len)) {
131 kfree(objp: p);
132 return ERR_PTR(error: -EFAULT);
133 }
134 return p;
135}
136#define memdup_sockptr(...) alloc_hooks(memdup_sockptr_noprof(__VA_ARGS__))
137
138static inline void *memdup_sockptr_nul_noprof(sockptr_t src, size_t len)
139{
140 char *p = kmalloc_track_caller_noprof(len + 1, GFP_KERNEL);
141
142 if (!p)
143 return ERR_PTR(error: -ENOMEM);
144 if (copy_from_sockptr(dst: p, src, size: len)) {
145 kfree(objp: p);
146 return ERR_PTR(error: -EFAULT);
147 }
148 p[len] = '\0';
149 return p;
150}
151#define memdup_sockptr_nul(...) alloc_hooks(memdup_sockptr_nul_noprof(__VA_ARGS__))
152
153static inline long strncpy_from_sockptr(char *dst, sockptr_t src, size_t count)
154{
155 if (sockptr_is_kernel(sockptr: src)) {
156 size_t len = min(strnlen(src.kernel, count - 1) + 1, count);
157
158 memcpy(dst, src.kernel, len);
159 return len;
160 }
161 return strncpy_from_user(dst, src: src.user, count);
162}
163
164static inline int check_zeroed_sockptr(sockptr_t src, size_t offset,
165 size_t size)
166{
167 if (!sockptr_is_kernel(sockptr: src))
168 return check_zeroed_user(from: src.user + offset, size);
169 return memchr_inv(p: src.kernel + offset, c: 0, size) == NULL;
170}
171
172#endif /* _LINUX_SOCKPTR_H */
173

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

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