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
53 /* Deprecated.
54 * This is unsafe, unless caller checked user provided optlen.
55 * Prefer copy_safe_from_sockptr() instead.
56 */
copy_from_sockptr(void * dst,sockptr_t src,size_t size)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 */
copy_safe_from_sockptr(void * dst,size_t ksize,sockptr_t optval,unsigned int optlen)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 if (copy_from_sockptr(dst, optval, ksize))
81 return -EFAULT;
82 return 0;
83 }
84
copy_to_sockptr_offset(sockptr_t dst,size_t offset,const void * src,size_t size)85 static inline int copy_to_sockptr_offset(sockptr_t dst, size_t offset,
86 const void *src, size_t size)
87 {
88 if (!sockptr_is_kernel(dst))
89 return copy_to_user(dst.user + offset, src, size);
90 memcpy(dst.kernel + offset, src, size);
91 return 0;
92 }
93
copy_to_sockptr(sockptr_t dst,const void * src,size_t size)94 static inline int copy_to_sockptr(sockptr_t dst, const void *src, size_t size)
95 {
96 return copy_to_sockptr_offset(dst, 0, src, size);
97 }
98
memdup_sockptr(sockptr_t src,size_t len)99 static inline void *memdup_sockptr(sockptr_t src, size_t len)
100 {
101 void *p = kmalloc_track_caller(len, GFP_USER | __GFP_NOWARN);
102
103 if (!p)
104 return ERR_PTR(-ENOMEM);
105 if (copy_from_sockptr(p, src, len)) {
106 kfree(p);
107 return ERR_PTR(-EFAULT);
108 }
109 return p;
110 }
111
memdup_sockptr_nul(sockptr_t src,size_t len)112 static inline void *memdup_sockptr_nul(sockptr_t src, size_t len)
113 {
114 char *p = kmalloc_track_caller(len + 1, GFP_KERNEL);
115
116 if (!p)
117 return ERR_PTR(-ENOMEM);
118 if (copy_from_sockptr(p, src, len)) {
119 kfree(p);
120 return ERR_PTR(-EFAULT);
121 }
122 p[len] = '\0';
123 return p;
124 }
125
strncpy_from_sockptr(char * dst,sockptr_t src,size_t count)126 static inline long strncpy_from_sockptr(char *dst, sockptr_t src, size_t count)
127 {
128 if (sockptr_is_kernel(src)) {
129 size_t len = min(strnlen(src.kernel, count - 1) + 1, count);
130
131 memcpy(dst, src.kernel, len);
132 return len;
133 }
134 return strncpy_from_user(dst, src.user, count);
135 }
136
check_zeroed_sockptr(sockptr_t src,size_t offset,size_t size)137 static inline int check_zeroed_sockptr(sockptr_t src, size_t offset,
138 size_t size)
139 {
140 if (!sockptr_is_kernel(src))
141 return check_zeroed_user(src.user + offset, size);
142 return memchr_inv(src.kernel + offset, 0, size) == NULL;
143 }
144
145 #endif /* _LINUX_SOCKPTR_H */
146