include/linux/uaccess.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef __LINUX_UACCESS_H__
   3 #define __LINUX_UACCESS_H__
   4
   5 #include <linux/sched.h>
   6 #include <linux/thread_info.h>
   7 #include <linux/kasan-checks.h>
   8
   9 #define uaccess_kernel() segment_eq(get_fs(), KERNEL_DS)
  10
  11 #include <asm/uaccess.h>
  12
  13 /*
  14  * Architectures should provide two primitives (raw_copy_{to,from}_user())
  15  * and get rid of their private instances of copy_{to,from}_user() and
  16  * __copy_{to,from}_user{,_inatomic}().
  17  *
  18  * raw_copy_{to,from}_user(to, from, size) should copy up to size bytes and
  19  * return the amount left to copy.  They should assume that access_ok() has
  20  * already been checked (and succeeded); they should *not* zero-pad anything.
  21  * No KASAN or object size checks either - those belong here.
  22  *
  23  * Both of these functions should attempt to copy size bytes starting at from
  24  * into the area starting at to.  They must not fetch or store anything
  25  * outside of those areas.  Return value must be between 0 (everything
  26  * copied successfully) and size (nothing copied).
  27  *
  28  * If raw_copy_{to,from}_user(to, from, size) returns N, size - N bytes starting
  29  * at to must become equal to the bytes fetched from the corresponding area
  30  * starting at from.  All data past to + size - N must be left unmodified.
  31  *
  32  * If copying succeeds, the return value must be 0.  If some data cannot be
  33  * fetched, it is permitted to copy less than had been fetched; the only
  34  * hard requirement is that not storing anything at all (i.e. returning size)
  35  * should happen only when nothing could be copied.  In other words, you don't
  36  * have to squeeze as much as possible - it is allowed, but not necessary.
  37  *
  38  * For raw_copy_from_user() to always points to kernel memory and no faults
  39  * on store should happen.  Interpretation of from is affected by set_fs().
  40  * For raw_copy_to_user() it's the other way round.
  41  *
  42  * Both can be inlined - it's up to architectures whether it wants to bother
  43  * with that.  They should not be used directly; they are used to implement
  44  * the 6 functions (copy_{to,from}_user(), __copy_{to,from}_user_inatomic())
  45  * that are used instead.  Out of those, __... ones are inlined.  Plain
  46  * copy_{to,from}_user() might or might not be inlined.  If you want them
  47  * inlined, have asm/uaccess.h define INLINE_COPY_{TO,FROM}_USER.
  48  *
  49  * NOTE: only copy_from_user() zero-pads the destination in case of short copy.
  50  * Neither __copy_from_user() nor __copy_from_user_inatomic() zero anything
  51  * at all; their callers absolutely must check the return value.
  52  *
  53  * Biarch ones should also provide raw_copy_in_user() - similar to the above,
  54  * but both source and destination are __user pointers (affected by set_fs()
  55  * as usual) and both source and destination can trigger faults.
  56  */
  57
  58 static __always_inline unsigned long
  59 __copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
  60 {
  61         kasan_check_write(to, n);
  62         check_object_size(to, n, false);
  63         return raw_copy_from_user(to, from, n);
  64 }
  65
  66 static __always_inline unsigned long
  67 __copy_from_user(void *to, const void __user *from, unsigned long n)
  68 {
  69         might_fault();
  70         kasan_check_write(to, n);
  71         check_object_size(to, n, false);
  72         return raw_copy_from_user(to, from, n);
  73 }
  74
  75 /**
  76  * __copy_to_user_inatomic: - Copy a block of data into user space, with less checking.
  77  * @to:   Destination address, in user space.
  78  * @from: Source address, in kernel space.
  79  * @n:    Number of bytes to copy.
  80  *
  81  * Context: User context only.
  82  *
  83  * Copy data from kernel space to user space.  Caller must check
  84  * the specified block with access_ok() before calling this function.
  85  * The caller should also make sure he pins the user space address
  86  * so that we don't result in page fault and sleep.
  87  */
  88 static __always_inline unsigned long
  89 __copy_to_user_inatomic(void __user *to, const void *from, unsigned long n)
  90 {
  91         kasan_check_read(from, n);
  92         check_object_size(from, n, true);
  93         return raw_copy_to_user(to, from, n);
  94 }
  95
  96 static __always_inline unsigned long
  97 __copy_to_user(void __user *to, const void *from, unsigned long n)
  98 {
  99         might_fault();
 100         kasan_check_read(from, n);
 101         check_object_size(from, n, true);
 102         return raw_copy_to_user(to, from, n);
 103 }
 104
 105 #ifdef INLINE_COPY_FROM_USER
 106 static inline unsigned long
 107 _copy_from_user(void *to, const void __user *from, unsigned long n)
 108 {
 109         unsigned long res = n;
 110         might_fault();
 111         if (likely(access_ok(from, n))) {
 112                 kasan_check_write(to, n);
 113                 res = raw_copy_from_user(to, from, n);
 114         }
 115         if (unlikely(res))
 116                 memset(to + (n - res), 0, res);
 117         return res;
 118 }
 119 #else
 120 extern unsigned long
 121 _copy_from_user(void *, const void __user *, unsigned long);
 122 #endif
 123
 124 #ifdef INLINE_COPY_TO_USER
 125 static inline unsigned long
 126 _copy_to_user(void __user *to, const void *from, unsigned long n)
 127 {
 128         might_fault();
 129         if (access_ok(to, n)) {
 130                 kasan_check_read(from, n);
 131                 n = raw_copy_to_user(to, from, n);
 132         }
 133         return n;
 134 }
 135 #else
 136 extern unsigned long
 137 _copy_to_user(void __user *, const void *, unsigned long);
 138 #endif
 139
 140 static __always_inline unsigned long __must_check
 141 copy_from_user(void *to, const void __user *from, unsigned long n)
 142 {
 143         if (likely(check_copy_size(to, n, false)))
 144                 n = _copy_from_user(to, from, n);
 145         return n;
 146 }
 147
 148 static __always_inline unsigned long __must_check
 149 copy_to_user(void __user *to, const void *from, unsigned long n)
 150 {
 151         if (likely(check_copy_size(from, n, true)))
 152                 n = _copy_to_user(to, from, n);
 153         return n;
 154 }
 155 #ifdef CONFIG_COMPAT
 156 static __always_inline unsigned long __must_check
 157 copy_in_user(void __user *to, const void __user *from, unsigned long n)
 158 {
 159         might_fault();
 160         if (access_ok(to, n) && access_ok(from, n))
 161                 n = raw_copy_in_user(to, from, n);
 162         return n;
 163 }
 164 #endif
 165
 166 static __always_inline void pagefault_disabled_inc(void)
 167 {
 168         current->pagefault_disabled++;
 169 }
 170
 171 static __always_inline void pagefault_disabled_dec(void)
 172 {
 173         current->pagefault_disabled--;
 174 }
 175
 176 /*
 177  * These routines enable/disable the pagefault handler. If disabled, it will
 178  * not take any locks and go straight to the fixup table.
 179  *
 180  * User access methods will not sleep when called from a pagefault_disabled()
 181  * environment.
 182  */
 183 static inline void pagefault_disable(void)
 184 {
 185         pagefault_disabled_inc();
 186         /*
 187          * make sure to have issued the store before a pagefault
 188          * can hit.
 189          */
 190         barrier();
 191 }
 192
 193 static inline void pagefault_enable(void)
 194 {
 195         /*
 196          * make sure to issue those last loads/stores before enabling
 197          * the pagefault handler again.
 198          */
 199         barrier();
 200         pagefault_disabled_dec();
 201 }
 202
 203 /*
 204  * Is the pagefault handler disabled? If so, user access methods will not sleep.
 205  */
 206 #define pagefault_disabled() (current->pagefault_disabled != 0)
 207
 208 /*
 209  * The pagefault handler is in general disabled by pagefault_disable() or
 210  * when in irq context (via in_atomic()).
 211  *
 212  * This function should only be used by the fault handlers. Other users should
 213  * stick to pagefault_disabled().
 214  * Please NEVER use preempt_disable() to disable the fault handler. With
 215  * !CONFIG_PREEMPT_COUNT, this is like a NOP. So the handler won't be disabled.
 216  * in_atomic() will report different values based on !CONFIG_PREEMPT_COUNT.
 217  */
 218 #define faulthandler_disabled() (pagefault_disabled() || in_atomic())
 219
 220 #ifndef ARCH_HAS_NOCACHE_UACCESS
 221
 222 static inline unsigned long __copy_from_user_inatomic_nocache(void *to,
 223                                 const void __user *from, unsigned long n)
 224 {
 225         return __copy_from_user_inatomic(to, from, n);
 226 }
 227
 228 #endif          /* ARCH_HAS_NOCACHE_UACCESS */
 229
 230 /*
 231  * probe_kernel_read(): safely attempt to read from a location
 232  * @dst: pointer to the buffer that shall take the data
 233  * @src: address to read from
 234  * @size: size of the data chunk
 235  *
 236  * Safely read from address @src to the buffer at @dst.  If a kernel fault
 237  * happens, handle that and return -EFAULT.
 238  */
 239 extern long probe_kernel_read(void *dst, const void *src, size_t size);
 240 extern long __probe_kernel_read(void *dst, const void *src, size_t size);
 241
 242 /*
 243  * probe_kernel_write(): safely attempt to write to a location
 244  * @dst: address to write to
 245  * @src: pointer to the data that shall be written
 246  * @size: size of the data chunk
 247  *
 248  * Safely write to address @dst from the buffer at @src.  If a kernel fault
 249  * happens, handle that and return -EFAULT.
 250  */
 251 extern long notrace probe_kernel_write(void *dst, const void *src, size_t size);
 252 extern long notrace __probe_kernel_write(void *dst, const void *src, size_t size);
 253
 254 extern long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count);
 255
 256 /**
 257  * probe_kernel_address(): safely attempt to read from a location
 258  * @addr: address to read from
 259  * @retval: read into this variable
 260  *
 261  * Returns 0 on success, or -EFAULT.
 262  */
 263 #define probe_kernel_address(addr, retval)              \
 264         probe_kernel_read(&retval, addr, sizeof(retval))
 265
 266 #ifndef user_access_begin
 267 #define user_access_begin() do { } while (0)
 268 #define user_access_end() do { } while (0)
 269 #define unsafe_get_user(x, ptr, err) do { if (unlikely(__get_user(x, ptr))) goto err; } while (0)
 270 #define unsafe_put_user(x, ptr, err) do { if (unlikely(__put_user(x, ptr))) goto err; } while (0)
 271 #endif
 272
 273 #ifdef CONFIG_HARDENED_USERCOPY
 274 void usercopy_warn(const char *name, const char *detail, bool to_user,
 275                    unsigned long offset, unsigned long len);
 276 void __noreturn usercopy_abort(const char *name, const char *detail,
 277                                bool to_user, unsigned long offset,
 278                                unsigned long len);
 279 #endif
 280
 281 #endif          /* __LINUX_UACCESS_H__ */