include/linux/uaccess.h

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