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TOMOYO Linux Cross Reference
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 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 static inline bool pagefault_disabled(void)
207 {
208         return current->pagefault_disabled != 0;
209 }
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_user_read(): safely attempt to read from a location in user space
247  * @dst: pointer to the buffer that shall take the data
248  * @src: address to read from
249  * @size: size of the data chunk
250  *
251  * Safely read from address @src to the buffer at @dst.  If a kernel fault
252  * happens, handle that and return -EFAULT.
253  */
254 extern long probe_user_read(void *dst, const void __user *src, size_t size);
255 extern long __probe_user_read(void *dst, const void __user *src, size_t size);
256 
257 /*
258  * probe_kernel_write(): safely attempt to write to a location
259  * @dst: address to write to
260  * @src: pointer to the data that shall be written
261  * @size: size of the data chunk
262  *
263  * Safely write to address @dst from the buffer at @src.  If a kernel fault
264  * happens, handle that and return -EFAULT.
265  */
266 extern long notrace probe_kernel_write(void *dst, const void *src, size_t size);
267 extern long notrace __probe_kernel_write(void *dst, const void *src, size_t size);
268 
269 extern long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count);
270 extern long strncpy_from_unsafe_user(char *dst, const void __user *unsafe_addr,
271                                      long count);
272 extern long strnlen_unsafe_user(const void __user *unsafe_addr, long count);
273 
274 /**
275  * probe_kernel_address(): safely attempt to read from a location
276  * @addr: address to read from
277  * @retval: read into this variable
278  *
279  * Returns 0 on success, or -EFAULT.
280  */
281 #define probe_kernel_address(addr, retval)              \
282         probe_kernel_read(&retval, addr, sizeof(retval))
283 
284 #ifndef user_access_begin
285 #define user_access_begin(ptr,len) access_ok(ptr, len)
286 #define user_access_end() do { } while (0)
287 #define unsafe_op_wrap(op, err) do { if (unlikely(op)) goto err; } while (0)
288 #define unsafe_get_user(x,p,e) unsafe_op_wrap(__get_user(x,p),e)
289 #define unsafe_put_user(x,p,e) unsafe_op_wrap(__put_user(x,p),e)
290 #define unsafe_copy_to_user(d,s,l,e) unsafe_op_wrap(__copy_to_user(d,s,l),e)
291 static inline unsigned long user_access_save(void) { return 0UL; }
292 static inline void user_access_restore(unsigned long flags) { }
293 #endif
294 
295 #ifdef CONFIG_HARDENED_USERCOPY
296 void usercopy_warn(const char *name, const char *detail, bool to_user,
297                    unsigned long offset, unsigned long len);
298 void __noreturn usercopy_abort(const char *name, const char *detail,
299                                bool to_user, unsigned long offset,
300                                unsigned long len);
301 #endif
302 
303 #endif          /* __LINUX_UACCESS_H__ */
304 

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