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 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 __must_check unsigned long
59 : __copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
60 : {
61 0 : instrument_copy_from_user(to, from, n);
62 : check_object_size(to, n, false);
63 0 : return raw_copy_from_user(to, from, n);
64 : }
65 :
66 : static __always_inline __must_check unsigned long
67 : __copy_from_user(void *to, const void __user *from, unsigned long n)
68 : {
69 : might_fault();
70 : if (should_fail_usercopy())
71 : return n;
72 : instrument_copy_from_user(to, from, n);
73 : check_object_size(to, n, false);
74 : return raw_copy_from_user(to, from, n);
75 : }
76 :
77 : /**
78 : * __copy_to_user_inatomic: - Copy a block of data into user space, with less checking.
79 : * @to: Destination address, in user space.
80 : * @from: Source address, in kernel space.
81 : * @n: Number of bytes to copy.
82 : *
83 : * Context: User context only.
84 : *
85 : * Copy data from kernel space to user space. Caller must check
86 : * the specified block with access_ok() before calling this function.
87 : * The caller should also make sure he pins the user space address
88 : * so that we don't result in page fault and sleep.
89 : */
90 : static __always_inline __must_check unsigned long
91 : __copy_to_user_inatomic(void __user *to, const void *from, unsigned long n)
92 : {
93 : if (should_fail_usercopy())
94 : return n;
95 0 : instrument_copy_to_user(to, from, n);
96 : check_object_size(from, n, true);
97 0 : return raw_copy_to_user(to, from, n);
98 : }
99 :
100 : static __always_inline __must_check unsigned long
101 : __copy_to_user(void __user *to, const void *from, unsigned long n)
102 : {
103 : might_fault();
104 : if (should_fail_usercopy())
105 : return n;
106 0 : instrument_copy_to_user(to, from, n);
107 : check_object_size(from, n, true);
108 0 : return raw_copy_to_user(to, from, n);
109 : }
110 :
111 : #ifdef INLINE_COPY_FROM_USER
112 : static inline __must_check unsigned long
113 0 : _copy_from_user(void *to, const void __user *from, unsigned long n)
114 : {
115 0 : unsigned long res = n;
116 : might_fault();
117 0 : if (!should_fail_usercopy() && likely(access_ok(from, n))) {
118 0 : instrument_copy_from_user(to, from, n);
119 0 : res = raw_copy_from_user(to, from, n);
120 : }
121 0 : if (unlikely(res))
122 0 : memset(to + (n - res), 0, res);
123 0 : return res;
124 : }
125 : #else
126 : extern __must_check unsigned long
127 : _copy_from_user(void *, const void __user *, unsigned long);
128 : #endif
129 :
130 : #ifdef INLINE_COPY_TO_USER
131 : static inline __must_check unsigned long
132 0 : _copy_to_user(void __user *to, const void *from, unsigned long n)
133 : {
134 : might_fault();
135 : if (should_fail_usercopy())
136 : return n;
137 0 : if (access_ok(to, n)) {
138 0 : instrument_copy_to_user(to, from, n);
139 0 : n = raw_copy_to_user(to, from, n);
140 : }
141 : return n;
142 : }
143 : #else
144 : extern __must_check unsigned long
145 : _copy_to_user(void __user *, const void *, unsigned long);
146 : #endif
147 :
148 : static __always_inline unsigned long __must_check
149 : copy_from_user(void *to, const void __user *from, unsigned long n)
150 : {
151 0 : if (likely(check_copy_size(to, n, false)))
152 0 : n = _copy_from_user(to, from, n);
153 : return n;
154 : }
155 :
156 : static __always_inline unsigned long __must_check
157 : copy_to_user(void __user *to, const void *from, unsigned long n)
158 : {
159 0 : if (likely(check_copy_size(from, n, true)))
160 0 : n = _copy_to_user(to, from, n);
161 : return n;
162 : }
163 :
164 : #ifndef copy_mc_to_kernel
165 : /*
166 : * Without arch opt-in this generic copy_mc_to_kernel() will not handle
167 : * #MC (or arch equivalent) during source read.
168 : */
169 : static inline unsigned long __must_check
170 : copy_mc_to_kernel(void *dst, const void *src, size_t cnt)
171 : {
172 : memcpy(dst, src, cnt);
173 : return 0;
174 : }
175 : #endif
176 :
177 : static __always_inline void pagefault_disabled_inc(void)
178 : {
179 0 : current->pagefault_disabled++;
180 : }
181 :
182 : static __always_inline void pagefault_disabled_dec(void)
183 : {
184 0 : current->pagefault_disabled--;
185 : }
186 :
187 : /*
188 : * These routines enable/disable the pagefault handler. If disabled, it will
189 : * not take any locks and go straight to the fixup table.
190 : *
191 : * User access methods will not sleep when called from a pagefault_disabled()
192 : * environment.
193 : */
194 : static inline void pagefault_disable(void)
195 : {
196 : pagefault_disabled_inc();
197 : /*
198 : * make sure to have issued the store before a pagefault
199 : * can hit.
200 : */
201 0 : barrier();
202 : }
203 :
204 : static inline void pagefault_enable(void)
205 : {
206 : /*
207 : * make sure to issue those last loads/stores before enabling
208 : * the pagefault handler again.
209 : */
210 0 : barrier();
211 : pagefault_disabled_dec();
212 : }
213 :
214 : /*
215 : * Is the pagefault handler disabled? If so, user access methods will not sleep.
216 : */
217 : static inline bool pagefault_disabled(void)
218 : {
219 0 : return current->pagefault_disabled != 0;
220 : }
221 :
222 : /*
223 : * The pagefault handler is in general disabled by pagefault_disable() or
224 : * when in irq context (via in_atomic()).
225 : *
226 : * This function should only be used by the fault handlers. Other users should
227 : * stick to pagefault_disabled().
228 : * Please NEVER use preempt_disable() to disable the fault handler. With
229 : * !CONFIG_PREEMPT_COUNT, this is like a NOP. So the handler won't be disabled.
230 : * in_atomic() will report different values based on !CONFIG_PREEMPT_COUNT.
231 : */
232 : #define faulthandler_disabled() (pagefault_disabled() || in_atomic())
233 :
234 : #ifndef ARCH_HAS_NOCACHE_UACCESS
235 :
236 : static inline __must_check unsigned long
237 : __copy_from_user_inatomic_nocache(void *to, const void __user *from,
238 : unsigned long n)
239 : {
240 0 : return __copy_from_user_inatomic(to, from, n);
241 : }
242 :
243 : #endif /* ARCH_HAS_NOCACHE_UACCESS */
244 :
245 : extern __must_check int check_zeroed_user(const void __user *from, size_t size);
246 :
247 : /**
248 : * copy_struct_from_user: copy a struct from userspace
249 : * @dst: Destination address, in kernel space. This buffer must be @ksize
250 : * bytes long.
251 : * @ksize: Size of @dst struct.
252 : * @src: Source address, in userspace.
253 : * @usize: (Alleged) size of @src struct.
254 : *
255 : * Copies a struct from userspace to kernel space, in a way that guarantees
256 : * backwards-compatibility for struct syscall arguments (as long as future
257 : * struct extensions are made such that all new fields are *appended* to the
258 : * old struct, and zeroed-out new fields have the same meaning as the old
259 : * struct).
260 : *
261 : * @ksize is just sizeof(*dst), and @usize should've been passed by userspace.
262 : * The recommended usage is something like the following:
263 : *
264 : * SYSCALL_DEFINE2(foobar, const struct foo __user *, uarg, size_t, usize)
265 : * {
266 : * int err;
267 : * struct foo karg = {};
268 : *
269 : * if (usize > PAGE_SIZE)
270 : * return -E2BIG;
271 : * if (usize < FOO_SIZE_VER0)
272 : * return -EINVAL;
273 : *
274 : * err = copy_struct_from_user(&karg, sizeof(karg), uarg, usize);
275 : * if (err)
276 : * return err;
277 : *
278 : * // ...
279 : * }
280 : *
281 : * There are three cases to consider:
282 : * * If @usize == @ksize, then it's copied verbatim.
283 : * * If @usize < @ksize, then the userspace has passed an old struct to a
284 : * newer kernel. The rest of the trailing bytes in @dst (@ksize - @usize)
285 : * are to be zero-filled.
286 : * * If @usize > @ksize, then the userspace has passed a new struct to an
287 : * older kernel. The trailing bytes unknown to the kernel (@usize - @ksize)
288 : * are checked to ensure they are zeroed, otherwise -E2BIG is returned.
289 : *
290 : * Returns (in all cases, some data may have been copied):
291 : * * -E2BIG: (@usize > @ksize) and there are non-zero trailing bytes in @src.
292 : * * -EFAULT: access to userspace failed.
293 : */
294 : static __always_inline __must_check int
295 : copy_struct_from_user(void *dst, size_t ksize, const void __user *src,
296 : size_t usize)
297 : {
298 0 : size_t size = min(ksize, usize);
299 0 : size_t rest = max(ksize, usize) - size;
300 :
301 : /* Deal with trailing bytes. */
302 0 : if (usize < ksize) {
303 0 : memset(dst + size, 0, rest);
304 0 : } else if (usize > ksize) {
305 0 : int ret = check_zeroed_user(src + size, rest);
306 0 : if (ret <= 0)
307 0 : return ret ?: -E2BIG;
308 : }
309 : /* Copy the interoperable parts of the struct. */
310 0 : if (copy_from_user(dst, src, size))
311 : return -EFAULT;
312 : return 0;
313 : }
314 :
315 : bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size);
316 :
317 : long copy_from_kernel_nofault(void *dst, const void *src, size_t size);
318 : long notrace copy_to_kernel_nofault(void *dst, const void *src, size_t size);
319 :
320 : long copy_from_user_nofault(void *dst, const void __user *src, size_t size);
321 : long notrace copy_to_user_nofault(void __user *dst, const void *src,
322 : size_t size);
323 :
324 : long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr,
325 : long count);
326 :
327 : long strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr,
328 : long count);
329 : long strnlen_user_nofault(const void __user *unsafe_addr, long count);
330 :
331 : #ifndef __get_kernel_nofault
332 : #define __get_kernel_nofault(dst, src, type, label) \
333 : do { \
334 : type __user *p = (type __force __user *)(src); \
335 : type data; \
336 : if (__get_user(data, p)) \
337 : goto label; \
338 : *(type *)dst = data; \
339 : } while (0)
340 :
341 : #define __put_kernel_nofault(dst, src, type, label) \
342 : do { \
343 : type __user *p = (type __force __user *)(dst); \
344 : type data = *(type *)src; \
345 : if (__put_user(data, p)) \
346 : goto label; \
347 : } while (0)
348 : #endif
349 :
350 : /**
351 : * get_kernel_nofault(): safely attempt to read from a location
352 : * @val: read into this variable
353 : * @ptr: address to read from
354 : *
355 : * Returns 0 on success, or -EFAULT.
356 : */
357 : #define get_kernel_nofault(val, ptr) ({ \
358 : const typeof(val) *__gk_ptr = (ptr); \
359 : copy_from_kernel_nofault(&(val), __gk_ptr, sizeof(val));\
360 : })
361 :
362 : #ifndef user_access_begin
363 : #define user_access_begin(ptr,len) access_ok(ptr, len)
364 : #define user_access_end() do { } while (0)
365 : #define unsafe_op_wrap(op, err) do { if (unlikely(op)) goto err; } while (0)
366 : #define unsafe_get_user(x,p,e) unsafe_op_wrap(__get_user(x,p),e)
367 : #define unsafe_put_user(x,p,e) unsafe_op_wrap(__put_user(x,p),e)
368 : #define unsafe_copy_to_user(d,s,l,e) unsafe_op_wrap(__copy_to_user(d,s,l),e)
369 : #define unsafe_copy_from_user(d,s,l,e) unsafe_op_wrap(__copy_from_user(d,s,l),e)
370 : static inline unsigned long user_access_save(void) { return 0UL; }
371 : static inline void user_access_restore(unsigned long flags) { }
372 : #endif
373 : #ifndef user_write_access_begin
374 : #define user_write_access_begin user_access_begin
375 : #define user_write_access_end user_access_end
376 : #endif
377 : #ifndef user_read_access_begin
378 : #define user_read_access_begin user_access_begin
379 : #define user_read_access_end user_access_end
380 : #endif
381 :
382 : #ifdef CONFIG_HARDENED_USERCOPY
383 : void __noreturn usercopy_abort(const char *name, const char *detail,
384 : bool to_user, unsigned long offset,
385 : unsigned long len);
386 : #endif
387 :
388 : #endif /* __LINUX_UACCESS_H__ */
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