1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef __LINUX_UACCESS_H__
3#define __LINUX_UACCESS_H__
4
5#include <linux/sched.h>
6#include <linux/thread_info.h>
7#include <linux/kasan-checks.h>
8
9#define uaccess_kernel() segment_eq(get_fs(), KERNEL_DS)
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 unsigned long
59__copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
60{
61 kasan_check_write(to, n);
62 check_object_size(to, n, false);
63 return raw_copy_from_user(to, from, n);
64}
65
66static __always_inline unsigned long
67__copy_from_user(void *to, const void __user *from, unsigned long n)
68{
69 might_fault();
70 kasan_check_write(to, n);
71 check_object_size(to, n, false);
72 return raw_copy_from_user(to, from, n);
73}
74
75/**
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.
80 *
81 * Context: User context only.
82 *
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.
87 */
88static __always_inline unsigned long
89__copy_to_user_inatomic(void __user *to, const void *from, unsigned long n)
90{
91 kasan_check_read(from, n);
92 check_object_size(from, n, true);
93 return raw_copy_to_user(to, from, n);
94}
95
96static __always_inline unsigned long
97__copy_to_user(void __user *to, const void *from, unsigned long n)
98{
99 might_fault();
100 kasan_check_read(from, n);
101 check_object_size(from, n, true);
102 return raw_copy_to_user(to, from, n);
103}
104
105#ifdef INLINE_COPY_FROM_USER
106static inline unsigned long
107_copy_from_user(void *to, const void __user *from, unsigned long n)
108{
109 unsigned long res = n;
110 might_fault();
111 if (likely(access_ok(from, n))) {
112 kasan_check_write(to, n);
113 res = raw_copy_from_user(to, from, n);
114 }
115 if (unlikely(res))
116 memset(to + (n - res), 0, res);
117 return res;
118}
119#else
120extern unsigned long
121_copy_from_user(void *, const void __user *, unsigned long);
122#endif
123
124#ifdef INLINE_COPY_TO_USER
125static inline unsigned long
126_copy_to_user(void __user *to, const void *from, unsigned long n)
127{
128 might_fault();
129 if (access_ok(to, n)) {
130 kasan_check_read(from, n);
131 n = raw_copy_to_user(to, from, n);
132 }
133 return n;
134}
135#else
136extern unsigned long
137_copy_to_user(void __user *, const void *, unsigned long);
138#endif
139
140static __always_inline unsigned long __must_check
141copy_from_user(void *to, const void __user *from, unsigned long n)
142{
143 if (likely(check_copy_size(to, n, false)))
144 n = _copy_from_user(to, from, n);
145 return n;
146}
147
148static __always_inline unsigned long __must_check
149copy_to_user(void __user *to, const void *from, unsigned long n)
150{
151 if (likely(check_copy_size(from, n, true)))
152 n = _copy_to_user(to, from, n);
153 return n;
154}
155#ifdef CONFIG_COMPAT
156static __always_inline unsigned long __must_check
157copy_in_user(void __user *to, const void __user *from, unsigned long n)
158{
159 might_fault();
160 if (access_ok(to, n) && access_ok(from, n))
161 n = raw_copy_in_user(to, from, n);
162 return n;
163}
164#endif
165
166static __always_inline void pagefault_disabled_inc(void)
167{
168 current->pagefault_disabled++;
169}
170
171static __always_inline void pagefault_disabled_dec(void)
172{
173 current->pagefault_disabled--;
174}
175
176/*
177 * These routines enable/disable the pagefault handler. If disabled, it will
178 * not take any locks and go straight to the fixup table.
179 *
180 * User access methods will not sleep when called from a pagefault_disabled()
181 * environment.
182 */
183static inline void pagefault_disable(void)
184{
185 pagefault_disabled_inc();
186 /*
187 * make sure to have issued the store before a pagefault
188 * can hit.
189 */
190 barrier();
191}
192
193static inline void pagefault_enable(void)
194{
195 /*
196 * make sure to issue those last loads/stores before enabling
197 * the pagefault handler again.
198 */
199 barrier();
200 pagefault_disabled_dec();
201}
202
203/*
204 * Is the pagefault handler disabled? If so, user access methods will not sleep.
205 */
206#define pagefault_disabled() (current->pagefault_disabled != 0)
207
208/*
209 * The pagefault handler is in general disabled by pagefault_disable() or
210 * when in irq context (via in_atomic()).
211 *
212 * This function should only be used by the fault handlers. Other users should
213 * stick to pagefault_disabled().
214 * Please NEVER use preempt_disable() to disable the fault handler. With
215 * !CONFIG_PREEMPT_COUNT, this is like a NOP. So the handler won't be disabled.
216 * in_atomic() will report different values based on !CONFIG_PREEMPT_COUNT.
217 */
218#define faulthandler_disabled() (pagefault_disabled() || in_atomic())
219
220#ifndef ARCH_HAS_NOCACHE_UACCESS
221
222static inline unsigned long __copy_from_user_inatomic_nocache(void *to,
223 const void __user *from, unsigned long n)
224{
225 return __copy_from_user_inatomic(to, from, n);
226}
227
228#endif /* ARCH_HAS_NOCACHE_UACCESS */
229
230/*
231 * probe_kernel_read(): safely attempt to read from a location
232 * @dst: pointer to the buffer that shall take the data
233 * @src: address to read from
234 * @size: size of the data chunk
235 *
236 * Safely read from address @src to the buffer at @dst. If a kernel fault
237 * happens, handle that and return -EFAULT.
238 */
239extern long probe_kernel_read(void *dst, const void *src, size_t size);
240extern long __probe_kernel_read(void *dst, const void *src, size_t size);
241
242/*
243 * probe_kernel_write(): safely attempt to write to a location
244 * @dst: address to write to
245 * @src: pointer to the data that shall be written
246 * @size: size of the data chunk
247 *
248 * Safely write to address @dst from the buffer at @src. If a kernel fault
249 * happens, handle that and return -EFAULT.
250 */
251extern long notrace probe_kernel_write(void *dst, const void *src, size_t size);
252extern long notrace __probe_kernel_write(void *dst, const void *src, size_t size);
253
254extern long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count);
255
256/**
257 * probe_kernel_address(): safely attempt to read from a location
258 * @addr: address to read from
259 * @retval: read into this variable
260 *
261 * Returns 0 on success, or -EFAULT.
262 */
263#define probe_kernel_address(addr, retval) \
264 probe_kernel_read(&retval, addr, sizeof(retval))
265
266#ifndef user_access_begin
267#define user_access_begin(ptr,len) access_ok(ptr, len)
268#define user_access_end() do { } while (0)
269#define unsafe_get_user(x, ptr, err) do { if (unlikely(__get_user(x, ptr))) goto err; } while (0)
270#define unsafe_put_user(x, ptr, err) do { if (unlikely(__put_user(x, ptr))) goto err; } while (0)
271#endif
272
273#ifdef CONFIG_HARDENED_USERCOPY
274void usercopy_warn(const char *name, const char *detail, bool to_user,
275 unsigned long offset, unsigned long len);
276void __noreturn usercopy_abort(const char *name, const char *detail,
277 bool to_user, unsigned long offset,
278 unsigned long len);
279#endif
280
281#endif /* __LINUX_UACCESS_H__ */
282