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