Line data Source code
1 : /* SPDX-License-Identifier: GPL-2.0 */
2 : #ifndef __LINUX_UACCESS_H__
3 : #define __LINUX_UACCESS_H__
4 :
5 : #include <linux/fault-inject-usercopy.h>
6 : #include <linux/instrumented.h>
7 : #include <linux/minmax.h>
8 : #include <linux/sched.h>
9 : #include <linux/thread_info.h>
10 :
11 : #include <asm/uaccess.h>
12 :
13 : /*
14 : * Architectures that support memory tagging (assigning tags to memory regions,
15 : * embedding these tags into addresses that point to these memory regions, and
16 : * checking that the memory and the pointer tags match on memory accesses)
17 : * redefine this macro to strip tags from pointers.
18 : *
19 : * Passing down mm_struct allows to define untagging rules on per-process
20 : * basis.
21 : *
22 : * It's defined as noop for architectures that don't support memory tagging.
23 : */
24 : #ifndef untagged_addr
25 : #define untagged_addr(addr) (addr)
26 : #endif
27 :
28 : #ifndef untagged_addr_remote
29 : #define untagged_addr_remote(mm, addr) ({ \
30 : mmap_assert_locked(mm); \
31 : untagged_addr(addr); \
32 : })
33 : #endif
34 :
35 : /*
36 : * Architectures should provide two primitives (raw_copy_{to,from}_user())
37 : * and get rid of their private instances of copy_{to,from}_user() and
38 : * __copy_{to,from}_user{,_inatomic}().
39 : *
40 : * raw_copy_{to,from}_user(to, from, size) should copy up to size bytes and
41 : * return the amount left to copy. They should assume that access_ok() has
42 : * already been checked (and succeeded); they should *not* zero-pad anything.
43 : * No KASAN or object size checks either - those belong here.
44 : *
45 : * Both of these functions should attempt to copy size bytes starting at from
46 : * into the area starting at to. They must not fetch or store anything
47 : * outside of those areas. Return value must be between 0 (everything
48 : * copied successfully) and size (nothing copied).
49 : *
50 : * If raw_copy_{to,from}_user(to, from, size) returns N, size - N bytes starting
51 : * at to must become equal to the bytes fetched from the corresponding area
52 : * starting at from. All data past to + size - N must be left unmodified.
53 : *
54 : * If copying succeeds, the return value must be 0. If some data cannot be
55 : * fetched, it is permitted to copy less than had been fetched; the only
56 : * hard requirement is that not storing anything at all (i.e. returning size)
57 : * should happen only when nothing could be copied. In other words, you don't
58 : * have to squeeze as much as possible - it is allowed, but not necessary.
59 : *
60 : * For raw_copy_from_user() to always points to kernel memory and no faults
61 : * on store should happen. Interpretation of from is affected by set_fs().
62 : * For raw_copy_to_user() it's the other way round.
63 : *
64 : * Both can be inlined - it's up to architectures whether it wants to bother
65 : * with that. They should not be used directly; they are used to implement
66 : * the 6 functions (copy_{to,from}_user(), __copy_{to,from}_user_inatomic())
67 : * that are used instead. Out of those, __... ones are inlined. Plain
68 : * copy_{to,from}_user() might or might not be inlined. If you want them
69 : * inlined, have asm/uaccess.h define INLINE_COPY_{TO,FROM}_USER.
70 : *
71 : * NOTE: only copy_from_user() zero-pads the destination in case of short copy.
72 : * Neither __copy_from_user() nor __copy_from_user_inatomic() zero anything
73 : * at all; their callers absolutely must check the return value.
74 : *
75 : * Biarch ones should also provide raw_copy_in_user() - similar to the above,
76 : * but both source and destination are __user pointers (affected by set_fs()
77 : * as usual) and both source and destination can trigger faults.
78 : */
79 :
80 : static __always_inline __must_check unsigned long
81 : __copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
82 : {
83 : unsigned long res;
84 :
85 0 : instrument_copy_from_user_before(to, from, n);
86 : check_object_size(to, n, false);
87 0 : res = raw_copy_from_user(to, from, n);
88 0 : instrument_copy_from_user_after(to, from, n, res);
89 : return res;
90 : }
91 :
92 : static __always_inline __must_check unsigned long
93 : __copy_from_user(void *to, const void __user *from, unsigned long n)
94 : {
95 : unsigned long res;
96 :
97 : might_fault();
98 : instrument_copy_from_user_before(to, from, n);
99 : if (should_fail_usercopy())
100 : return n;
101 : check_object_size(to, n, false);
102 : res = raw_copy_from_user(to, from, n);
103 : instrument_copy_from_user_after(to, from, n, res);
104 : return res;
105 : }
106 :
107 : /**
108 : * __copy_to_user_inatomic: - Copy a block of data into user space, with less checking.
109 : * @to: Destination address, in user space.
110 : * @from: Source address, in kernel space.
111 : * @n: Number of bytes to copy.
112 : *
113 : * Context: User context only.
114 : *
115 : * Copy data from kernel space to user space. Caller must check
116 : * the specified block with access_ok() before calling this function.
117 : * The caller should also make sure he pins the user space address
118 : * so that we don't result in page fault and sleep.
119 : */
120 : static __always_inline __must_check unsigned long
121 : __copy_to_user_inatomic(void __user *to, const void *from, unsigned long n)
122 : {
123 : if (should_fail_usercopy())
124 : return n;
125 0 : instrument_copy_to_user(to, from, n);
126 : check_object_size(from, n, true);
127 0 : return raw_copy_to_user(to, from, n);
128 : }
129 :
130 : static __always_inline __must_check unsigned long
131 : __copy_to_user(void __user *to, const void *from, unsigned long n)
132 : {
133 : might_fault();
134 : if (should_fail_usercopy())
135 : return n;
136 0 : instrument_copy_to_user(to, from, n);
137 : check_object_size(from, n, true);
138 0 : return raw_copy_to_user(to, from, n);
139 : }
140 :
141 : #ifdef INLINE_COPY_FROM_USER
142 : static inline __must_check unsigned long
143 0 : _copy_from_user(void *to, const void __user *from, unsigned long n)
144 : {
145 0 : unsigned long res = n;
146 : might_fault();
147 0 : if (!should_fail_usercopy() && likely(access_ok(from, n))) {
148 0 : instrument_copy_from_user_before(to, from, n);
149 0 : res = raw_copy_from_user(to, from, n);
150 : instrument_copy_from_user_after(to, from, n, res);
151 : }
152 0 : if (unlikely(res))
153 0 : memset(to + (n - res), 0, res);
154 0 : return res;
155 : }
156 : #else
157 : extern __must_check unsigned long
158 : _copy_from_user(void *, const void __user *, unsigned long);
159 : #endif
160 :
161 : #ifdef INLINE_COPY_TO_USER
162 : static inline __must_check unsigned long
163 0 : _copy_to_user(void __user *to, const void *from, unsigned long n)
164 : {
165 : might_fault();
166 : if (should_fail_usercopy())
167 : return n;
168 0 : if (access_ok(to, n)) {
169 0 : instrument_copy_to_user(to, from, n);
170 0 : n = raw_copy_to_user(to, from, n);
171 : }
172 : return n;
173 : }
174 : #else
175 : extern __must_check unsigned long
176 : _copy_to_user(void __user *, const void *, unsigned long);
177 : #endif
178 :
179 : static __always_inline unsigned long __must_check
180 : copy_from_user(void *to, const void __user *from, unsigned long n)
181 : {
182 0 : if (check_copy_size(to, n, false))
183 0 : n = _copy_from_user(to, from, n);
184 : return n;
185 : }
186 :
187 : static __always_inline unsigned long __must_check
188 : copy_to_user(void __user *to, const void *from, unsigned long n)
189 : {
190 0 : if (check_copy_size(from, n, true))
191 0 : n = _copy_to_user(to, from, n);
192 : return n;
193 : }
194 :
195 : #ifndef copy_mc_to_kernel
196 : /*
197 : * Without arch opt-in this generic copy_mc_to_kernel() will not handle
198 : * #MC (or arch equivalent) during source read.
199 : */
200 : static inline unsigned long __must_check
201 : copy_mc_to_kernel(void *dst, const void *src, size_t cnt)
202 : {
203 : memcpy(dst, src, cnt);
204 : return 0;
205 : }
206 : #endif
207 :
208 : static __always_inline void pagefault_disabled_inc(void)
209 : {
210 0 : current->pagefault_disabled++;
211 : }
212 :
213 : static __always_inline void pagefault_disabled_dec(void)
214 : {
215 0 : current->pagefault_disabled--;
216 : }
217 :
218 : /*
219 : * These routines enable/disable the pagefault handler. If disabled, it will
220 : * not take any locks and go straight to the fixup table.
221 : *
222 : * User access methods will not sleep when called from a pagefault_disabled()
223 : * environment.
224 : */
225 : static inline void pagefault_disable(void)
226 : {
227 : pagefault_disabled_inc();
228 : /*
229 : * make sure to have issued the store before a pagefault
230 : * can hit.
231 : */
232 0 : barrier();
233 : }
234 :
235 : static inline void pagefault_enable(void)
236 : {
237 : /*
238 : * make sure to issue those last loads/stores before enabling
239 : * the pagefault handler again.
240 : */
241 0 : barrier();
242 : pagefault_disabled_dec();
243 : }
244 :
245 : /*
246 : * Is the pagefault handler disabled? If so, user access methods will not sleep.
247 : */
248 : static inline bool pagefault_disabled(void)
249 : {
250 0 : return current->pagefault_disabled != 0;
251 : }
252 :
253 : /*
254 : * The pagefault handler is in general disabled by pagefault_disable() or
255 : * when in irq context (via in_atomic()).
256 : *
257 : * This function should only be used by the fault handlers. Other users should
258 : * stick to pagefault_disabled().
259 : * Please NEVER use preempt_disable() to disable the fault handler. With
260 : * !CONFIG_PREEMPT_COUNT, this is like a NOP. So the handler won't be disabled.
261 : * in_atomic() will report different values based on !CONFIG_PREEMPT_COUNT.
262 : */
263 : #define faulthandler_disabled() (pagefault_disabled() || in_atomic())
264 :
265 : #ifndef CONFIG_ARCH_HAS_SUBPAGE_FAULTS
266 :
267 : /**
268 : * probe_subpage_writeable: probe the user range for write faults at sub-page
269 : * granularity (e.g. arm64 MTE)
270 : * @uaddr: start of address range
271 : * @size: size of address range
272 : *
273 : * Returns 0 on success, the number of bytes not probed on fault.
274 : *
275 : * It is expected that the caller checked for the write permission of each
276 : * page in the range either by put_user() or GUP. The architecture port can
277 : * implement a more efficient get_user() probing if the same sub-page faults
278 : * are triggered by either a read or a write.
279 : */
280 : static inline size_t probe_subpage_writeable(char __user *uaddr, size_t size)
281 : {
282 : return 0;
283 : }
284 :
285 : #endif /* CONFIG_ARCH_HAS_SUBPAGE_FAULTS */
286 :
287 : #ifndef ARCH_HAS_NOCACHE_UACCESS
288 :
289 : static inline __must_check unsigned long
290 : __copy_from_user_inatomic_nocache(void *to, const void __user *from,
291 : unsigned long n)
292 : {
293 0 : return __copy_from_user_inatomic(to, from, n);
294 : }
295 :
296 : #endif /* ARCH_HAS_NOCACHE_UACCESS */
297 :
298 : extern __must_check int check_zeroed_user(const void __user *from, size_t size);
299 :
300 : /**
301 : * copy_struct_from_user: copy a struct from userspace
302 : * @dst: Destination address, in kernel space. This buffer must be @ksize
303 : * bytes long.
304 : * @ksize: Size of @dst struct.
305 : * @src: Source address, in userspace.
306 : * @usize: (Alleged) size of @src struct.
307 : *
308 : * Copies a struct from userspace to kernel space, in a way that guarantees
309 : * backwards-compatibility for struct syscall arguments (as long as future
310 : * struct extensions are made such that all new fields are *appended* to the
311 : * old struct, and zeroed-out new fields have the same meaning as the old
312 : * struct).
313 : *
314 : * @ksize is just sizeof(*dst), and @usize should've been passed by userspace.
315 : * The recommended usage is something like the following:
316 : *
317 : * SYSCALL_DEFINE2(foobar, const struct foo __user *, uarg, size_t, usize)
318 : * {
319 : * int err;
320 : * struct foo karg = {};
321 : *
322 : * if (usize > PAGE_SIZE)
323 : * return -E2BIG;
324 : * if (usize < FOO_SIZE_VER0)
325 : * return -EINVAL;
326 : *
327 : * err = copy_struct_from_user(&karg, sizeof(karg), uarg, usize);
328 : * if (err)
329 : * return err;
330 : *
331 : * // ...
332 : * }
333 : *
334 : * There are three cases to consider:
335 : * * If @usize == @ksize, then it's copied verbatim.
336 : * * If @usize < @ksize, then the userspace has passed an old struct to a
337 : * newer kernel. The rest of the trailing bytes in @dst (@ksize - @usize)
338 : * are to be zero-filled.
339 : * * If @usize > @ksize, then the userspace has passed a new struct to an
340 : * older kernel. The trailing bytes unknown to the kernel (@usize - @ksize)
341 : * are checked to ensure they are zeroed, otherwise -E2BIG is returned.
342 : *
343 : * Returns (in all cases, some data may have been copied):
344 : * * -E2BIG: (@usize > @ksize) and there are non-zero trailing bytes in @src.
345 : * * -EFAULT: access to userspace failed.
346 : */
347 : static __always_inline __must_check int
348 : copy_struct_from_user(void *dst, size_t ksize, const void __user *src,
349 : size_t usize)
350 : {
351 0 : size_t size = min(ksize, usize);
352 0 : size_t rest = max(ksize, usize) - size;
353 :
354 : /* Double check if ksize is larger than a known object size. */
355 0 : if (WARN_ON_ONCE(ksize > __builtin_object_size(dst, 1)))
356 : return -E2BIG;
357 :
358 : /* Deal with trailing bytes. */
359 0 : if (usize < ksize) {
360 0 : memset(dst + size, 0, rest);
361 0 : } else if (usize > ksize) {
362 0 : int ret = check_zeroed_user(src + size, rest);
363 0 : if (ret <= 0)
364 0 : return ret ?: -E2BIG;
365 : }
366 : /* Copy the interoperable parts of the struct. */
367 0 : if (copy_from_user(dst, src, size))
368 : return -EFAULT;
369 : return 0;
370 : }
371 :
372 : bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size);
373 :
374 : long copy_from_kernel_nofault(void *dst, const void *src, size_t size);
375 : long notrace copy_to_kernel_nofault(void *dst, const void *src, size_t size);
376 :
377 : long copy_from_user_nofault(void *dst, const void __user *src, size_t size);
378 : long notrace copy_to_user_nofault(void __user *dst, const void *src,
379 : size_t size);
380 :
381 : long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr,
382 : long count);
383 :
384 : long strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr,
385 : long count);
386 : long strnlen_user_nofault(const void __user *unsafe_addr, long count);
387 :
388 : #ifndef __get_kernel_nofault
389 : #define __get_kernel_nofault(dst, src, type, label) \
390 : do { \
391 : type __user *p = (type __force __user *)(src); \
392 : type data; \
393 : if (__get_user(data, p)) \
394 : goto label; \
395 : *(type *)dst = data; \
396 : } while (0)
397 :
398 : #define __put_kernel_nofault(dst, src, type, label) \
399 : do { \
400 : type __user *p = (type __force __user *)(dst); \
401 : type data = *(type *)src; \
402 : if (__put_user(data, p)) \
403 : goto label; \
404 : } while (0)
405 : #endif
406 :
407 : /**
408 : * get_kernel_nofault(): safely attempt to read from a location
409 : * @val: read into this variable
410 : * @ptr: address to read from
411 : *
412 : * Returns 0 on success, or -EFAULT.
413 : */
414 : #define get_kernel_nofault(val, ptr) ({ \
415 : const typeof(val) *__gk_ptr = (ptr); \
416 : copy_from_kernel_nofault(&(val), __gk_ptr, sizeof(val));\
417 : })
418 :
419 : #ifndef user_access_begin
420 : #define user_access_begin(ptr,len) access_ok(ptr, len)
421 : #define user_access_end() do { } while (0)
422 : #define unsafe_op_wrap(op, err) do { if (unlikely(op)) goto err; } while (0)
423 : #define unsafe_get_user(x,p,e) unsafe_op_wrap(__get_user(x,p),e)
424 : #define unsafe_put_user(x,p,e) unsafe_op_wrap(__put_user(x,p),e)
425 : #define unsafe_copy_to_user(d,s,l,e) unsafe_op_wrap(__copy_to_user(d,s,l),e)
426 : #define unsafe_copy_from_user(d,s,l,e) unsafe_op_wrap(__copy_from_user(d,s,l),e)
427 : static inline unsigned long user_access_save(void) { return 0UL; }
428 : static inline void user_access_restore(unsigned long flags) { }
429 : #endif
430 : #ifndef user_write_access_begin
431 : #define user_write_access_begin user_access_begin
432 : #define user_write_access_end user_access_end
433 : #endif
434 : #ifndef user_read_access_begin
435 : #define user_read_access_begin user_access_begin
436 : #define user_read_access_end user_access_end
437 : #endif
438 :
439 : #ifdef CONFIG_HARDENED_USERCOPY
440 : void __noreturn usercopy_abort(const char *name, const char *detail,
441 : bool to_user, unsigned long offset,
442 : unsigned long len);
443 : #endif
444 :
445 : #endif /* __LINUX_UACCESS_H__ */
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