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
sockptr_is_kernel(sockptr_t sockptr)22 static inline bool sockptr_is_kernel(sockptr_t sockptr)
23 {
24 return sockptr.is_kernel;
25 }
26
KERNEL_SOCKPTR(void * p)27 static inline sockptr_t KERNEL_SOCKPTR(void *p)
28 {
29 return (sockptr_t) { .kernel = p, .is_kernel = true };
30 }
31
USER_SOCKPTR(void __user * p)32 static inline sockptr_t USER_SOCKPTR(void __user *p)
33 {
34 return (sockptr_t) { .user = p };
35 }
36
sockptr_is_null(sockptr_t sockptr)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
copy_from_sockptr_offset(void * dst,sockptr_t src,size_t offset,size_t size)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
copy_from_sockptr(void * dst,sockptr_t src,size_t size)53 static inline int copy_from_sockptr(void *dst, sockptr_t src, size_t size)
54 {
55 return copy_from_sockptr_offset(dst, src, 0, size);
56 }
57
copy_struct_from_sockptr(void * dst,size_t ksize,sockptr_t src,size_t usize)58 static inline int copy_struct_from_sockptr(void *dst, size_t ksize,
59 sockptr_t src, size_t usize)
60 {
61 size_t size = min(ksize, usize);
62 size_t rest = max(ksize, usize) - size;
63
64 if (!sockptr_is_kernel(src))
65 return copy_struct_from_user(dst, ksize, src.user, size);
66
67 if (usize < ksize) {
68 memset(dst + size, 0, rest);
69 } else if (usize > ksize) {
70 char *p = src.kernel;
71
72 while (rest--) {
73 if (*p++)
74 return -E2BIG;
75 }
76 }
77 memcpy(dst, src.kernel, size);
78 return 0;
79 }
80
copy_to_sockptr_offset(sockptr_t dst,size_t offset,const void * src,size_t size)81 static inline int copy_to_sockptr_offset(sockptr_t dst, size_t offset,
82 const void *src, size_t size)
83 {
84 if (!sockptr_is_kernel(dst))
85 return copy_to_user(dst.user + offset, src, size);
86 memcpy(dst.kernel + offset, src, size);
87 return 0;
88 }
89
copy_to_sockptr(sockptr_t dst,const void * src,size_t size)90 static inline int copy_to_sockptr(sockptr_t dst, const void *src, size_t size)
91 {
92 return copy_to_sockptr_offset(dst, 0, src, size);
93 }
94
memdup_sockptr(sockptr_t src,size_t len)95 static inline void *memdup_sockptr(sockptr_t src, size_t len)
96 {
97 void *p = kmalloc_track_caller(len, GFP_USER | __GFP_NOWARN);
98
99 if (!p)
100 return ERR_PTR(-ENOMEM);
101 if (copy_from_sockptr(p, src, len)) {
102 kfree(p);
103 return ERR_PTR(-EFAULT);
104 }
105 return p;
106 }
107
memdup_sockptr_nul(sockptr_t src,size_t len)108 static inline void *memdup_sockptr_nul(sockptr_t src, size_t len)
109 {
110 char *p = kmalloc_track_caller(len + 1, GFP_KERNEL);
111
112 if (!p)
113 return ERR_PTR(-ENOMEM);
114 if (copy_from_sockptr(p, src, len)) {
115 kfree(p);
116 return ERR_PTR(-EFAULT);
117 }
118 p[len] = '\0';
119 return p;
120 }
121
strncpy_from_sockptr(char * dst,sockptr_t src,size_t count)122 static inline long strncpy_from_sockptr(char *dst, sockptr_t src, size_t count)
123 {
124 if (sockptr_is_kernel(src)) {
125 size_t len = min(strnlen(src.kernel, count - 1) + 1, count);
126
127 memcpy(dst, src.kernel, len);
128 return len;
129 }
130 return strncpy_from_user(dst, src.user, count);
131 }
132
check_zeroed_sockptr(sockptr_t src,size_t offset,size_t size)133 static inline int check_zeroed_sockptr(sockptr_t src, size_t offset,
134 size_t size)
135 {
136 if (!sockptr_is_kernel(src))
137 return check_zeroed_user(src.user + offset, size);
138 return memchr_inv(src.kernel + offset, 0, size) == NULL;
139 }
140
141 #endif /* _LINUX_SOCKPTR_H */
142