xref: /openbmc/linux/include/linux/uaccess.h (revision 428e106a)
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
__copy_from_user_inatomic(void * to,const void __user * from,unsigned long n)81 __copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
82 {
83 	unsigned long res;
84 
85 	instrument_copy_from_user_before(to, from, n);
86 	check_object_size(to, n, false);
87 	res = raw_copy_from_user(to, from, n);
88 	instrument_copy_from_user_after(to, from, n, res);
89 	return res;
90 }
91 
92 static __always_inline __must_check unsigned long
__copy_from_user(void * to,const void __user * from,unsigned long n)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
__copy_to_user_inatomic(void __user * to,const void * from,unsigned long n)121 __copy_to_user_inatomic(void __user *to, const void *from, unsigned long n)
122 {
123 	if (should_fail_usercopy())
124 		return n;
125 	instrument_copy_to_user(to, from, n);
126 	check_object_size(from, n, true);
127 	return raw_copy_to_user(to, from, n);
128 }
129 
130 static __always_inline __must_check unsigned long
__copy_to_user(void __user * to,const void * from,unsigned long n)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 	instrument_copy_to_user(to, from, n);
137 	check_object_size(from, n, true);
138 	return raw_copy_to_user(to, from, n);
139 }
140 
141 #ifdef INLINE_COPY_FROM_USER
142 static inline __must_check unsigned long
_copy_from_user(void * to,const void __user * from,unsigned long n)143 _copy_from_user(void *to, const void __user *from, unsigned long n)
144 {
145 	unsigned long res = n;
146 	might_fault();
147 	if (!should_fail_usercopy() && likely(access_ok(from, n))) {
148 		instrument_copy_from_user_before(to, from, n);
149 		res = raw_copy_from_user(to, from, n);
150 		instrument_copy_from_user_after(to, from, n, res);
151 	}
152 	if (unlikely(res))
153 		memset(to + (n - res), 0, res);
154 	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
_copy_to_user(void __user * to,const void * from,unsigned long n)163 _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 	if (access_ok(to, n)) {
169 		instrument_copy_to_user(to, from, n);
170 		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
copy_from_user(void * to,const void __user * from,unsigned long n)180 copy_from_user(void *to, const void __user *from, unsigned long n)
181 {
182 	if (check_copy_size(to, n, false))
183 		n = _copy_from_user(to, from, n);
184 	return n;
185 }
186 
187 static __always_inline unsigned long __must_check
copy_to_user(void __user * to,const void * from,unsigned long n)188 copy_to_user(void __user *to, const void *from, unsigned long n)
189 {
190 	if (check_copy_size(from, n, true))
191 		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
copy_mc_to_kernel(void * dst,const void * src,size_t cnt)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 
pagefault_disabled_inc(void)208 static __always_inline void pagefault_disabled_inc(void)
209 {
210 	current->pagefault_disabled++;
211 }
212 
pagefault_disabled_dec(void)213 static __always_inline void pagefault_disabled_dec(void)
214 {
215 	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  */
pagefault_disable(void)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 	barrier();
233 }
234 
pagefault_enable(void)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 	barrier();
242 	pagefault_disabled_dec();
243 }
244 
245 /*
246  * Is the pagefault handler disabled? If so, user access methods will not sleep.
247  */
pagefault_disabled(void)248 static inline bool pagefault_disabled(void)
249 {
250 	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  */
probe_subpage_writeable(char __user * uaddr,size_t size)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
__copy_from_user_inatomic_nocache(void * to,const void __user * from,unsigned long n)290 __copy_from_user_inatomic_nocache(void *to, const void __user *from,
291 				  unsigned long n)
292 {
293 	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
copy_struct_from_user(void * dst,size_t ksize,const void __user * src,size_t usize)348 copy_struct_from_user(void *dst, size_t ksize, const void __user *src,
349 		      size_t usize)
350 {
351 	size_t size = min(ksize, usize);
352 	size_t rest = max(ksize, usize) - size;
353 
354 	/* Double check if ksize is larger than a known object size. */
355 	if (WARN_ON_ONCE(ksize > __builtin_object_size(dst, 1)))
356 		return -E2BIG;
357 
358 	/* Deal with trailing bytes. */
359 	if (usize < ksize) {
360 		memset(dst + size, 0, rest);
361 	} else if (usize > ksize) {
362 		int ret = check_zeroed_user(src + size, rest);
363 		if (ret <= 0)
364 			return ret ?: -E2BIG;
365 	}
366 	/* Copy the interoperable parts of the struct. */
367 	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)
user_access_save(void)427 static inline unsigned long user_access_save(void) { return 0UL; }
user_access_restore(unsigned long flags)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__ */
446