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
58static __always_inline __must_check unsigned long
59__copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
60{
61	unsigned long res;
62
63	instrument_copy_from_user_before(to, from, n);
64	check_object_size(to, n, false);
65	res = raw_copy_from_user(to, from, n);
66	instrument_copy_from_user_after(to, from, n, res);
67	return res;
68}
69
70static __always_inline __must_check unsigned long
71__copy_from_user(void *to, const void __user *from, unsigned long n)
72{
73	unsigned long res;
74
75	might_fault();
76	instrument_copy_from_user_before(to, from, n);
77	if (should_fail_usercopy())
78		return n;
79	check_object_size(to, n, false);
80	res = raw_copy_from_user(to, from, n);
81	instrument_copy_from_user_after(to, from, n, res);
82	return res;
83}
84
85/**
86 * __copy_to_user_inatomic: - Copy a block of data into user space, with less checking.
87 * @to:   Destination address, in user space.
88 * @from: Source address, in kernel space.
89 * @n:    Number of bytes to copy.
90 *
91 * Context: User context only.
92 *
93 * Copy data from kernel space to user space.  Caller must check
94 * the specified block with access_ok() before calling this function.
95 * The caller should also make sure he pins the user space address
96 * so that we don't result in page fault and sleep.
97 */
98static __always_inline __must_check unsigned long
99__copy_to_user_inatomic(void __user *to, const void *from, unsigned long n)
100{
101	if (should_fail_usercopy())
102		return n;
103	instrument_copy_to_user(to, from, n);
104	check_object_size(from, n, true);
105	return raw_copy_to_user(to, from, n);
106}
107
108static __always_inline __must_check unsigned long
109__copy_to_user(void __user *to, const void *from, unsigned long n)
110{
111	might_fault();
112	if (should_fail_usercopy())
113		return n;
114	instrument_copy_to_user(to, from, n);
115	check_object_size(from, n, true);
116	return raw_copy_to_user(to, from, n);
117}
118
119#ifdef INLINE_COPY_FROM_USER
120static inline __must_check unsigned long
121_copy_from_user(void *to, const void __user *from, unsigned long n)
122{
123	unsigned long res = n;
124	might_fault();
125	if (!should_fail_usercopy() && likely(access_ok(from, n))) {
126		instrument_copy_from_user_before(to, from, n);
127		res = raw_copy_from_user(to, from, n);
128		instrument_copy_from_user_after(to, from, n, res);
129	}
130	if (unlikely(res))
131		memset(to + (n - res), 0, res);
132	return res;
133}
134#else
135extern __must_check unsigned long
136_copy_from_user(void *, const void __user *, unsigned long);
137#endif
138
139#ifdef INLINE_COPY_TO_USER
140static inline __must_check unsigned long
141_copy_to_user(void __user *to, const void *from, unsigned long n)
142{
143	might_fault();
144	if (should_fail_usercopy())
145		return n;
146	if (access_ok(to, n)) {
147		instrument_copy_to_user(to, from, n);
148		n = raw_copy_to_user(to, from, n);
149	}
150	return n;
151}
152#else
153extern __must_check unsigned long
154_copy_to_user(void __user *, const void *, unsigned long);
155#endif
156
157static __always_inline unsigned long __must_check
158copy_from_user(void *to, const void __user *from, unsigned long n)
159{
160	if (check_copy_size(to, n, false))
161		n = _copy_from_user(to, from, n);
162	return n;
163}
164
165static __always_inline unsigned long __must_check
166copy_to_user(void __user *to, const void *from, unsigned long n)
167{
168	if (check_copy_size(from, n, true))
169		n = _copy_to_user(to, from, n);
170	return n;
171}
172
173#ifndef copy_mc_to_kernel
174/*
175 * Without arch opt-in this generic copy_mc_to_kernel() will not handle
176 * #MC (or arch equivalent) during source read.
177 */
178static inline unsigned long __must_check
179copy_mc_to_kernel(void *dst, const void *src, size_t cnt)
180{
181	memcpy(dst, src, cnt);
182	return 0;
183}
184#endif
185
186static __always_inline void pagefault_disabled_inc(void)
187{
188	current->pagefault_disabled++;
189}
190
191static __always_inline void pagefault_disabled_dec(void)
192{
193	current->pagefault_disabled--;
194}
195
196/*
197 * These routines enable/disable the pagefault handler. If disabled, it will
198 * not take any locks and go straight to the fixup table.
199 *
200 * User access methods will not sleep when called from a pagefault_disabled()
201 * environment.
202 */
203static inline void pagefault_disable(void)
204{
205	pagefault_disabled_inc();
206	/*
207	 * make sure to have issued the store before a pagefault
208	 * can hit.
209	 */
210	barrier();
211}
212
213static inline void pagefault_enable(void)
214{
215	/*
216	 * make sure to issue those last loads/stores before enabling
217	 * the pagefault handler again.
218	 */
219	barrier();
220	pagefault_disabled_dec();
221}
222
223/*
224 * Is the pagefault handler disabled? If so, user access methods will not sleep.
225 */
226static inline bool pagefault_disabled(void)
227{
228	return current->pagefault_disabled != 0;
229}
230
231/*
232 * The pagefault handler is in general disabled by pagefault_disable() or
233 * when in irq context (via in_atomic()).
234 *
235 * This function should only be used by the fault handlers. Other users should
236 * stick to pagefault_disabled().
237 * Please NEVER use preempt_disable() to disable the fault handler. With
238 * !CONFIG_PREEMPT_COUNT, this is like a NOP. So the handler won't be disabled.
239 * in_atomic() will report different values based on !CONFIG_PREEMPT_COUNT.
240 */
241#define faulthandler_disabled() (pagefault_disabled() || in_atomic())
242
243#ifndef CONFIG_ARCH_HAS_SUBPAGE_FAULTS
244
245/**
246 * probe_subpage_writeable: probe the user range for write faults at sub-page
247 *			    granularity (e.g. arm64 MTE)
248 * @uaddr: start of address range
249 * @size: size of address range
250 *
251 * Returns 0 on success, the number of bytes not probed on fault.
252 *
253 * It is expected that the caller checked for the write permission of each
254 * page in the range either by put_user() or GUP. The architecture port can
255 * implement a more efficient get_user() probing if the same sub-page faults
256 * are triggered by either a read or a write.
257 */
258static inline size_t probe_subpage_writeable(char __user *uaddr, size_t size)
259{
260	return 0;
261}
262
263#endif /* CONFIG_ARCH_HAS_SUBPAGE_FAULTS */
264
265#ifndef ARCH_HAS_NOCACHE_UACCESS
266
267static inline __must_check unsigned long
268__copy_from_user_inatomic_nocache(void *to, const void __user *from,
269				  unsigned long n)
270{
271	return __copy_from_user_inatomic(to, from, n);
272}
273
274#endif		/* ARCH_HAS_NOCACHE_UACCESS */
275
276extern __must_check int check_zeroed_user(const void __user *from, size_t size);
277
278/**
279 * copy_struct_from_user: copy a struct from userspace
280 * @dst:   Destination address, in kernel space. This buffer must be @ksize
281 *         bytes long.
282 * @ksize: Size of @dst struct.
283 * @src:   Source address, in userspace.
284 * @usize: (Alleged) size of @src struct.
285 *
286 * Copies a struct from userspace to kernel space, in a way that guarantees
287 * backwards-compatibility for struct syscall arguments (as long as future
288 * struct extensions are made such that all new fields are *appended* to the
289 * old struct, and zeroed-out new fields have the same meaning as the old
290 * struct).
291 *
292 * @ksize is just sizeof(*dst), and @usize should've been passed by userspace.
293 * The recommended usage is something like the following:
294 *
295 *   SYSCALL_DEFINE2(foobar, const struct foo __user *, uarg, size_t, usize)
296 *   {
297 *      int err;
298 *      struct foo karg = {};
299 *
300 *      if (usize > PAGE_SIZE)
301 *        return -E2BIG;
302 *      if (usize < FOO_SIZE_VER0)
303 *        return -EINVAL;
304 *
305 *      err = copy_struct_from_user(&karg, sizeof(karg), uarg, usize);
306 *      if (err)
307 *        return err;
308 *
309 *      // ...
310 *   }
311 *
312 * There are three cases to consider:
313 *  * If @usize == @ksize, then it's copied verbatim.
314 *  * If @usize < @ksize, then the userspace has passed an old struct to a
315 *    newer kernel. The rest of the trailing bytes in @dst (@ksize - @usize)
316 *    are to be zero-filled.
317 *  * If @usize > @ksize, then the userspace has passed a new struct to an
318 *    older kernel. The trailing bytes unknown to the kernel (@usize - @ksize)
319 *    are checked to ensure they are zeroed, otherwise -E2BIG is returned.
320 *
321 * Returns (in all cases, some data may have been copied):
322 *  * -E2BIG:  (@usize > @ksize) and there are non-zero trailing bytes in @src.
323 *  * -EFAULT: access to userspace failed.
324 */
325static __always_inline __must_check int
326copy_struct_from_user(void *dst, size_t ksize, const void __user *src,
327		      size_t usize)
328{
329	size_t size = min(ksize, usize);
330	size_t rest = max(ksize, usize) - size;
331
332	/* Deal with trailing bytes. */
333	if (usize < ksize) {
334		memset(dst + size, 0, rest);
335	} else if (usize > ksize) {
336		int ret = check_zeroed_user(src + size, rest);
337		if (ret <= 0)
338			return ret ?: -E2BIG;
339	}
340	/* Copy the interoperable parts of the struct. */
341	if (copy_from_user(dst, src, size))
342		return -EFAULT;
343	return 0;
344}
345
346bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size);
347
348long copy_from_kernel_nofault(void *dst, const void *src, size_t size);
349long notrace copy_to_kernel_nofault(void *dst, const void *src, size_t size);
350
351long copy_from_user_nofault(void *dst, const void __user *src, size_t size);
352long notrace copy_to_user_nofault(void __user *dst, const void *src,
353		size_t size);
354
355long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr,
356		long count);
357
358long strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr,
359		long count);
360long strnlen_user_nofault(const void __user *unsafe_addr, long count);
361
362#ifndef __get_kernel_nofault
363#define __get_kernel_nofault(dst, src, type, label)	\
364do {							\
365	type __user *p = (type __force __user *)(src);	\
366	type data;					\
367	if (__get_user(data, p))			\
368		goto label;				\
369	*(type *)dst = data;				\
370} while (0)
371
372#define __put_kernel_nofault(dst, src, type, label)	\
373do {							\
374	type __user *p = (type __force __user *)(dst);	\
375	type data = *(type *)src;			\
376	if (__put_user(data, p))			\
377		goto label;				\
378} while (0)
379#endif
380
381/**
382 * get_kernel_nofault(): safely attempt to read from a location
383 * @val: read into this variable
384 * @ptr: address to read from
385 *
386 * Returns 0 on success, or -EFAULT.
387 */
388#define get_kernel_nofault(val, ptr) ({				\
389	const typeof(val) *__gk_ptr = (ptr);			\
390	copy_from_kernel_nofault(&(val), __gk_ptr, sizeof(val));\
391})
392
393#ifndef user_access_begin
394#define user_access_begin(ptr,len) access_ok(ptr, len)
395#define user_access_end() do { } while (0)
396#define unsafe_op_wrap(op, err) do { if (unlikely(op)) goto err; } while (0)
397#define unsafe_get_user(x,p,e) unsafe_op_wrap(__get_user(x,p),e)
398#define unsafe_put_user(x,p,e) unsafe_op_wrap(__put_user(x,p),e)
399#define unsafe_copy_to_user(d,s,l,e) unsafe_op_wrap(__copy_to_user(d,s,l),e)
400#define unsafe_copy_from_user(d,s,l,e) unsafe_op_wrap(__copy_from_user(d,s,l),e)
401static inline unsigned long user_access_save(void) { return 0UL; }
402static inline void user_access_restore(unsigned long flags) { }
403#endif
404#ifndef user_write_access_begin
405#define user_write_access_begin user_access_begin
406#define user_write_access_end user_access_end
407#endif
408#ifndef user_read_access_begin
409#define user_read_access_begin user_access_begin
410#define user_read_access_end user_access_end
411#endif
412
413#ifdef CONFIG_HARDENED_USERCOPY
414void __noreturn usercopy_abort(const char *name, const char *detail,
415			       bool to_user, unsigned long offset,
416			       unsigned long len);
417#endif
418
419#endif		/* __LINUX_UACCESS_H__ */
420