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Linux/include/linux/uaccess.h

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  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 #ifdef CONFIG_HARDENED_USERCOPY
277 void usercopy_warn(const char *name, const char *detail, bool to_user,
278                    unsigned long offset, unsigned long len);
279 void __noreturn usercopy_abort(const char *name, const char *detail,
280                                bool to_user, unsigned long offset,
281                                unsigned long len);
282 #endif
283 
284 #endif          /* __LINUX_UACCESS_H__ */
285 

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