include/linux/sockptr.h

   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  * Returns 0 for success, or number of bytes not copied on error.
  58  */
  59 static inline int copy_from_sockptr(void *dst, sockptr_t src, size_t size)
  60 {
  61         return copy_from_sockptr_offset(dst, src, 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  */
  77 static 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, optval, ksize))
  83                 return -EFAULT;
  84         return 0;
  85 }
  86
  87 static 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(src))
  94                 return copy_struct_from_user(dst, ksize, src.user, 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
 110 static 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(dst))
 114                 return copy_to_user(dst.user + offset, src, size);
 115         memcpy(dst.kernel + offset, src, size);
 116         return 0;
 117 }
 118
 119 static inline int copy_to_sockptr(sockptr_t dst, const void *src, size_t size)
 120 {
 121         return copy_to_sockptr_offset(dst, 0, src, size);
 122 }
 123
 124 static 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(-ENOMEM);
 130         if (copy_from_sockptr(p, src, len)) {
 131                 kfree(p);
 132                 return ERR_PTR(-EFAULT);
 133         }
 134         return p;
 135 }
 136 #define memdup_sockptr(...)     alloc_hooks(memdup_sockptr_noprof(__VA_ARGS__))
 137
 138 static 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(-ENOMEM);
 144         if (copy_from_sockptr(p, src, len)) {
 145                 kfree(p);
 146                 return ERR_PTR(-EFAULT);
 147         }
 148         p[len] = '\0';
 149         return p;
 150 }
 151 #define memdup_sockptr_nul(...) alloc_hooks(memdup_sockptr_nul_noprof(__VA_ARGS__))
 152
 153 static inline long strncpy_from_sockptr(char *dst, sockptr_t src, size_t count)
 154 {
 155         if (sockptr_is_kernel(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.user, count);
 162 }
 163
 164 static inline int check_zeroed_sockptr(sockptr_t src, size_t offset,
 165                                        size_t size)
 166 {
 167         if (!sockptr_is_kernel(src))
 168                 return check_zeroed_user(src.user + offset, size);
 169         return memchr_inv(src.kernel + offset, 0, size) == NULL;
 170 }
 171
 172 #endif /* _LINUX_SOCKPTR_H */