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
14 typedef struct {
15 union {
16 void *kernel;
17 void __user *user;
18 };
19 bool is_kernel : 1;
20 } sockptr_t;
21
22 static inline bool sockptr_is_kernel(sockptr_t sockptr)
23 {
24 return sockptr.is_kernel;
25 }
26
27 static inline sockptr_t KERNEL_SOCKPTR(void *p)
28 {
29 return (sockptr_t) { .kernel = p, .is_kernel = true };
30 }
31
32 static inline sockptr_t USER_SOCKPTR(void __user *p)
33 {
34 return (sockptr_t) { .user = p };
35 }
36
37 static 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
44 static inline int copy_from_sockptr_offset(void *dst, sockptr_t src,
45 size_t offset, size_t size)
46 {
47 if (!sockptr_is_kernel(src))
48 return copy_from_user(dst, src.user + offset, 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 static inline int copy_from_sockptr(void *dst, sockptr_t src, size_t size)
58 {
59 return copy_from_sockptr_offset(dst, src, 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 */
75 static 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, optval, ksize);
81 }
82
83 static 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(src))
90 return copy_struct_from_user(dst, ksize, src.user, 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
106 static 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(dst))
110 return copy_to_user(dst.user + offset, src, size);
111 memcpy(dst.kernel + offset, src, size);
112 return 0;
113 }
114
115 static inline int copy_to_sockptr(sockptr_t dst, const void *src, size_t size)
116 {
117 return copy_to_sockptr_offset(dst, 0, src, size);
118 }
119
120 static inline void *memdup_sockptr_noprof(sockptr_t src, size_t len)
121 {
122 void *p = kmalloc_track_caller_noprof(len, GFP_USER | __GFP_NOWARN);
123
124 if (!p)
125 return ERR_PTR(-ENOMEM);
126 if (copy_from_sockptr(p, src, len)) {
127 kfree(p);
128 return ERR_PTR(-EFAULT);
129 }
130 return p;
131 }
132 #define memdup_sockptr(...) alloc_hooks(memdup_sockptr_noprof(__VA_ARGS__))
133
134 static inline void *memdup_sockptr_nul_noprof(sockptr_t src, size_t len)
135 {
136 char *p = kmalloc_track_caller_noprof(len + 1, GFP_KERNEL);
137
138 if (!p)
139 return ERR_PTR(-ENOMEM);
140 if (copy_from_sockptr(p, src, len)) {
141 kfree(p);
142 return ERR_PTR(-EFAULT);
143 }
144 p[len] = '\0';
145 return p;
146 }
147 #define memdup_sockptr_nul(...) alloc_hooks(memdup_sockptr_nul_noprof(__VA_ARGS__))
148
149 static inline long strncpy_from_sockptr(char *dst, sockptr_t src, size_t count)
150 {
151 if (sockptr_is_kernel(src)) {
152 size_t len = min(strnlen(src.kernel, count - 1) + 1, count);
153
154 memcpy(dst, src.kernel, len);
155 return len;
156 }
157 return strncpy_from_user(dst, src.user, count);
158 }
159
160 static inline int check_zeroed_sockptr(sockptr_t src, size_t offset,
161 size_t size)
162 {
163 if (!sockptr_is_kernel(src))
164 return check_zeroed_user(src.user + offset, size);
165 return memchr_inv(src.kernel + offset, 0, size) == NULL;
166 }
167
168 #endif /* _LINUX_SOCKPTR_H */
169
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