1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __LINUX_UACCESS_H__
3 #define __LINUX_UACCESS_H__
5 #include <linux/sched.h>
6 #include <linux/thread_info.h>
7 #include <linux/kasan-checks.h>
9 #define uaccess_kernel() segment_eq(get_fs(), KERNEL_DS)
11 #include <asm/uaccess.h>
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}().
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.
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).
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.
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.
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.
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.
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.
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.
58 static __always_inline __must_check
unsigned long
59 __copy_from_user_inatomic(void *to
, const void __user
*from
, unsigned long n
)
61 kasan_check_write(to
, n
);
62 check_object_size(to
, n
, false);
63 return raw_copy_from_user(to
, from
, n
);
66 static __always_inline __must_check
unsigned long
67 __copy_from_user(void *to
, const void __user
*from
, unsigned long n
)
70 kasan_check_write(to
, n
);
71 check_object_size(to
, n
, false);
72 return raw_copy_from_user(to
, from
, n
);
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.
81 * Context: User context only.
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.
88 static __always_inline __must_check
unsigned long
89 __copy_to_user_inatomic(void __user
*to
, const void *from
, unsigned long n
)
91 kasan_check_read(from
, n
);
92 check_object_size(from
, n
, true);
93 return raw_copy_to_user(to
, from
, n
);
96 static __always_inline __must_check
unsigned long
97 __copy_to_user(void __user
*to
, const void *from
, unsigned long n
)
100 kasan_check_read(from
, n
);
101 check_object_size(from
, n
, true);
102 return raw_copy_to_user(to
, from
, n
);
105 #ifdef INLINE_COPY_FROM_USER
106 static inline __must_check
unsigned long
107 _copy_from_user(void *to
, const void __user
*from
, unsigned long n
)
109 unsigned long res
= n
;
111 if (likely(access_ok(from
, n
))) {
112 kasan_check_write(to
, n
);
113 res
= raw_copy_from_user(to
, from
, n
);
116 memset(to
+ (n
- res
), 0, res
);
120 extern __must_check
unsigned long
121 _copy_from_user(void *, const void __user
*, unsigned long);
124 #ifdef INLINE_COPY_TO_USER
125 static inline __must_check
unsigned long
126 _copy_to_user(void __user
*to
, const void *from
, unsigned long n
)
129 if (access_ok(to
, n
)) {
130 kasan_check_read(from
, n
);
131 n
= raw_copy_to_user(to
, from
, n
);
136 extern __must_check
unsigned long
137 _copy_to_user(void __user
*, const void *, unsigned long);
140 static __always_inline
unsigned long __must_check
141 copy_from_user(void *to
, const void __user
*from
, unsigned long n
)
143 if (likely(check_copy_size(to
, n
, false)))
144 n
= _copy_from_user(to
, from
, n
);
148 static __always_inline
unsigned long __must_check
149 copy_to_user(void __user
*to
, const void *from
, unsigned long n
)
151 if (likely(check_copy_size(from
, n
, true)))
152 n
= _copy_to_user(to
, from
, n
);
156 static __always_inline
unsigned long __must_check
157 copy_in_user(void __user
*to
, const void __user
*from
, unsigned long n
)
160 if (access_ok(to
, n
) && access_ok(from
, n
))
161 n
= raw_copy_in_user(to
, from
, n
);
166 static __always_inline
void pagefault_disabled_inc(void)
168 current
->pagefault_disabled
++;
171 static __always_inline
void pagefault_disabled_dec(void)
173 current
->pagefault_disabled
--;
177 * These routines enable/disable the pagefault handler. If disabled, it will
178 * not take any locks and go straight to the fixup table.
180 * User access methods will not sleep when called from a pagefault_disabled()
183 static inline void pagefault_disable(void)
185 pagefault_disabled_inc();
187 * make sure to have issued the store before a pagefault
193 static inline void pagefault_enable(void)
196 * make sure to issue those last loads/stores before enabling
197 * the pagefault handler again.
200 pagefault_disabled_dec();
204 * Is the pagefault handler disabled? If so, user access methods will not sleep.
206 static inline bool pagefault_disabled(void)
208 return current
->pagefault_disabled
!= 0;
212 * The pagefault handler is in general disabled by pagefault_disable() or
213 * when in irq context (via in_atomic()).
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.
221 #define faulthandler_disabled() (pagefault_disabled() || in_atomic())
223 #ifndef ARCH_HAS_NOCACHE_UACCESS
225 static inline __must_check
unsigned long
226 __copy_from_user_inatomic_nocache(void *to
, const void __user
*from
,
229 return __copy_from_user_inatomic(to
, from
, n
);
232 #endif /* ARCH_HAS_NOCACHE_UACCESS */
234 extern __must_check
int check_zeroed_user(const void __user
*from
, size_t size
);
237 * copy_struct_from_user: copy a struct from userspace
238 * @dst: Destination address, in kernel space. This buffer must be @ksize
240 * @ksize: Size of @dst struct.
241 * @src: Source address, in userspace.
242 * @usize: (Alleged) size of @src struct.
244 * Copies a struct from userspace to kernel space, in a way that guarantees
245 * backwards-compatibility for struct syscall arguments (as long as future
246 * struct extensions are made such that all new fields are *appended* to the
247 * old struct, and zeroed-out new fields have the same meaning as the old
250 * @ksize is just sizeof(*dst), and @usize should've been passed by userspace.
251 * The recommended usage is something like the following:
253 * SYSCALL_DEFINE2(foobar, const struct foo __user *, uarg, size_t, usize)
256 * struct foo karg = {};
258 * if (usize > PAGE_SIZE)
260 * if (usize < FOO_SIZE_VER0)
263 * err = copy_struct_from_user(&karg, sizeof(karg), uarg, usize);
270 * There are three cases to consider:
271 * * If @usize == @ksize, then it's copied verbatim.
272 * * If @usize < @ksize, then the userspace has passed an old struct to a
273 * newer kernel. The rest of the trailing bytes in @dst (@ksize - @usize)
274 * are to be zero-filled.
275 * * If @usize > @ksize, then the userspace has passed a new struct to an
276 * older kernel. The trailing bytes unknown to the kernel (@usize - @ksize)
277 * are checked to ensure they are zeroed, otherwise -E2BIG is returned.
279 * Returns (in all cases, some data may have been copied):
280 * * -E2BIG: (@usize > @ksize) and there are non-zero trailing bytes in @src.
281 * * -EFAULT: access to userspace failed.
283 static __always_inline __must_check
int
284 copy_struct_from_user(void *dst
, size_t ksize
, const void __user
*src
,
287 size_t size
= min(ksize
, usize
);
288 size_t rest
= max(ksize
, usize
) - size
;
290 /* Deal with trailing bytes. */
292 memset(dst
+ size
, 0, rest
);
293 } else if (usize
> ksize
) {
294 int ret
= check_zeroed_user(src
+ size
, rest
);
296 return ret
?: -E2BIG
;
298 /* Copy the interoperable parts of the struct. */
299 if (copy_from_user(dst
, src
, size
))
305 * probe_kernel_read(): safely attempt to read from a location
306 * @dst: pointer to the buffer that shall take the data
307 * @src: address to read from
308 * @size: size of the data chunk
310 * Safely read from address @src to the buffer at @dst. If a kernel fault
311 * happens, handle that and return -EFAULT.
313 extern long probe_kernel_read(void *dst
, const void *src
, size_t size
);
314 extern long probe_kernel_read_strict(void *dst
, const void *src
, size_t size
);
315 extern long __probe_kernel_read(void *dst
, const void *src
, size_t size
);
318 * probe_user_read(): safely attempt to read from a location in user space
319 * @dst: pointer to the buffer that shall take the data
320 * @src: address to read from
321 * @size: size of the data chunk
323 * Safely read from address @src to the buffer at @dst. If a kernel fault
324 * happens, handle that and return -EFAULT.
326 extern long probe_user_read(void *dst
, const void __user
*src
, size_t size
);
327 extern long __probe_user_read(void *dst
, const void __user
*src
, size_t size
);
330 * probe_kernel_write(): safely attempt to write to a location
331 * @dst: address to write to
332 * @src: pointer to the data that shall be written
333 * @size: size of the data chunk
335 * Safely write to address @dst from the buffer at @src. If a kernel fault
336 * happens, handle that and return -EFAULT.
338 extern long notrace
probe_kernel_write(void *dst
, const void *src
, size_t size
);
339 extern long notrace
__probe_kernel_write(void *dst
, const void *src
, size_t size
);
342 * probe_user_write(): safely attempt to write to a location in user space
343 * @dst: address to write to
344 * @src: pointer to the data that shall be written
345 * @size: size of the data chunk
347 * Safely write to address @dst from the buffer at @src. If a kernel fault
348 * happens, handle that and return -EFAULT.
350 extern long notrace
probe_user_write(void __user
*dst
, const void *src
, size_t size
);
351 extern long notrace
__probe_user_write(void __user
*dst
, const void *src
, size_t size
);
353 extern long strncpy_from_unsafe(char *dst
, const void *unsafe_addr
, long count
);
354 extern long strncpy_from_unsafe_strict(char *dst
, const void *unsafe_addr
,
356 extern long __strncpy_from_unsafe(char *dst
, const void *unsafe_addr
, long count
);
357 extern long strncpy_from_unsafe_user(char *dst
, const void __user
*unsafe_addr
,
359 extern long strnlen_unsafe_user(const void __user
*unsafe_addr
, long count
);
362 * probe_kernel_address(): safely attempt to read from a location
363 * @addr: address to read from
364 * @retval: read into this variable
366 * Returns 0 on success, or -EFAULT.
368 #define probe_kernel_address(addr, retval) \
369 probe_kernel_read(&retval, addr, sizeof(retval))
371 #ifndef user_access_begin
372 #define user_access_begin(ptr,len) access_ok(ptr, len)
373 #define user_access_end() do { } while (0)
374 #define unsafe_op_wrap(op, err) do { if (unlikely(op)) goto err; } while (0)
375 #define unsafe_get_user(x,p,e) unsafe_op_wrap(__get_user(x,p),e)
376 #define unsafe_put_user(x,p,e) unsafe_op_wrap(__put_user(x,p),e)
377 #define unsafe_copy_to_user(d,s,l,e) unsafe_op_wrap(__copy_to_user(d,s,l),e)
378 static inline unsigned long user_access_save(void) { return 0UL; }
379 static inline void user_access_restore(unsigned long flags
) { }
382 #ifdef CONFIG_HARDENED_USERCOPY
383 void usercopy_warn(const char *name
, const char *detail
, bool to_user
,
384 unsigned long offset
, unsigned long len
);
385 void __noreturn
usercopy_abort(const char *name
, const char *detail
,
386 bool to_user
, unsigned long offset
,
390 #endif /* __LINUX_UACCESS_H__ */