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 VERIFY_READ 0
10#define VERIFY_WRITE 1
11
12#define uaccess_kernel() segment_eq(get_fs(), KERNEL_DS)
13
14#include <asm/uaccess.h>
15
16/*
17 * Architectures should provide two primitives (raw_copy_{to,from}_user())
18 * and get rid of their private instances of copy_{to,from}_user() and
19 * __copy_{to,from}_user{,_inatomic}().
20 *
21 * raw_copy_{to,from}_user(to, from, size) should copy up to size bytes and
22 * return the amount left to copy. They should assume that access_ok() has
23 * already been checked (and succeeded); they should *not* zero-pad anything.
24 * No KASAN or object size checks either - those belong here.
25 *
26 * Both of these functions should attempt to copy size bytes starting at from
27 * into the area starting at to. They must not fetch or store anything
28 * outside of those areas. Return value must be between 0 (everything
29 * copied successfully) and size (nothing copied).
30 *
31 * If raw_copy_{to,from}_user(to, from, size) returns N, size - N bytes starting
32 * at to must become equal to the bytes fetched from the corresponding area
33 * starting at from. All data past to + size - N must be left unmodified.
34 *
35 * If copying succeeds, the return value must be 0. If some data cannot be
36 * fetched, it is permitted to copy less than had been fetched; the only
37 * hard requirement is that not storing anything at all (i.e. returning size)
38 * should happen only when nothing could be copied. In other words, you don't
39 * have to squeeze as much as possible - it is allowed, but not necessary.
40 *
41 * For raw_copy_from_user() to always points to kernel memory and no faults
42 * on store should happen. Interpretation of from is affected by set_fs().
43 * For raw_copy_to_user() it's the other way round.
44 *
45 * Both can be inlined - it's up to architectures whether it wants to bother
46 * with that. They should not be used directly; they are used to implement
47 * the 6 functions (copy_{to,from}_user(), __copy_{to,from}_user_inatomic())
48 * that are used instead. Out of those, __... ones are inlined. Plain
49 * copy_{to,from}_user() might or might not be inlined. If you want them
50 * inlined, have asm/uaccess.h define INLINE_COPY_{TO,FROM}_USER.
51 *
52 * NOTE: only copy_from_user() zero-pads the destination in case of short copy.
53 * Neither __copy_from_user() nor __copy_from_user_inatomic() zero anything
54 * at all; their callers absolutely must check the return value.
55 *
56 * Biarch ones should also provide raw_copy_in_user() - similar to the above,
57 * but both source and destination are __user pointers (affected by set_fs()
58 * as usual) and both source and destination can trigger faults.
59 */
60
61static __always_inline unsigned long
62__copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
63{
64 kasan_check_write(to, n);
65 check_object_size(to, n, false);
66 return raw_copy_from_user(to, from, n);
67}
68
69static __always_inline unsigned long
70__copy_from_user(void *to, const void __user *from, unsigned long n)
71{
72 might_fault();
73 kasan_check_write(to, n);
74 check_object_size(to, n, false);
75 return raw_copy_from_user(to, from, n);
76}
77
78/**
79 * __copy_to_user_inatomic: - Copy a block of data into user space, with less checking.
80 * @to: Destination address, in user space.
81 * @from: Source address, in kernel space.
82 * @n: Number of bytes to copy.
83 *
84 * Context: User context only.
85 *
86 * Copy data from kernel space to user space. Caller must check
87 * the specified block with access_ok() before calling this function.
88 * The caller should also make sure he pins the user space address
89 * so that we don't result in page fault and sleep.
90 */
91static __always_inline unsigned long
92__copy_to_user_inatomic(void __user *to, const void *from, unsigned long n)
93{
94 kasan_check_read(from, n);
95 check_object_size(from, n, true);
96 return raw_copy_to_user(to, from, n);
97}
98
99static __always_inline unsigned long
100__copy_to_user(void __user *to, const void *from, unsigned long n)
101{
102 might_fault();
103 kasan_check_read(from, n);
104 check_object_size(from, n, true);
105 return raw_copy_to_user(to, from, n);
106}
107
108#ifdef INLINE_COPY_FROM_USER
109static inline unsigned long
110_copy_from_user(void *to, const void __user *from, unsigned long n)
111{
112 unsigned long res = n;
113 might_fault();
114 if (likely(access_ok(VERIFY_READ, from, n))) {
115 kasan_check_write(to, n);
116 res = raw_copy_from_user(to, from, n);
117 }
118 if (unlikely(res))
119 memset(to + (n - res), 0, res);
120 return res;
121}
122#else
123extern unsigned long
124_copy_from_user(void *, const void __user *, unsigned long);
125#endif
126
127#ifdef INLINE_COPY_TO_USER
128static inline unsigned long
129_copy_to_user(void __user *to, const void *from, unsigned long n)
130{
131 might_fault();
132 if (access_ok(VERIFY_WRITE, to, n)) {
133 kasan_check_read(from, n);
134 n = raw_copy_to_user(to, from, n);
135 }
136 return n;
137}
138#else
139extern unsigned long
140_copy_to_user(void __user *, const void *, unsigned long);
141#endif
142
143static __always_inline unsigned long __must_check
144copy_from_user(void *to, const void __user *from, unsigned long n)
145{
146 if (likely(check_copy_size(to, n, false)))
147 n = _copy_from_user(to, from, n);
148 return n;
149}
150
151static __always_inline unsigned long __must_check
152copy_to_user(void __user *to, const void *from, unsigned long n)
153{
154 if (likely(check_copy_size(from, n, true)))
155 n = _copy_to_user(to, from, n);
156 return n;
157}
158#ifdef CONFIG_COMPAT
159static __always_inline unsigned long __must_check
160copy_in_user(void __user *to, const void __user *from, unsigned long n)
161{
162 might_fault();
163 if (access_ok(VERIFY_WRITE, to, n) && access_ok(VERIFY_READ, from, n))
164 n = raw_copy_in_user(to, from, n);
165 return n;
166}
167#endif
168
169static __always_inline void pagefault_disabled_inc(void)
170{
171 current->pagefault_disabled++;
172}
173
174static __always_inline void pagefault_disabled_dec(void)
175{
176 current->pagefault_disabled--;
177}
178
179/*
180 * These routines enable/disable the pagefault handler. If disabled, it will
181 * not take any locks and go straight to the fixup table.
182 *
183 * User access methods will not sleep when called from a pagefault_disabled()
184 * environment.
185 */
186static inline void pagefault_disable(void)
187{
188 pagefault_disabled_inc();
189 /*
190 * make sure to have issued the store before a pagefault
191 * can hit.
192 */
193 barrier();
194}
195
196static inline void pagefault_enable(void)
197{
198 /*
199 * make sure to issue those last loads/stores before enabling
200 * the pagefault handler again.
201 */
202 barrier();
203 pagefault_disabled_dec();
204}
205
206/*
207 * Is the pagefault handler disabled? If so, user access methods will not sleep.
208 */
209#define pagefault_disabled() (current->pagefault_disabled != 0)
210
211/*
212 * The pagefault handler is in general disabled by pagefault_disable() or
213 * when in irq context (via in_atomic()).
214 *
215 * This function should only be used by the fault handlers. Other users should
216 * stick to pagefault_disabled().
217 * Please NEVER use preempt_disable() to disable the fault handler. With
218 * !CONFIG_PREEMPT_COUNT, this is like a NOP. So the handler won't be disabled.
219 * in_atomic() will report different values based on !CONFIG_PREEMPT_COUNT.
220 */
221#define faulthandler_disabled() (pagefault_disabled() || in_atomic())
222
223#ifndef ARCH_HAS_NOCACHE_UACCESS
224
225static inline unsigned long __copy_from_user_inatomic_nocache(void *to,
226 const void __user *from, unsigned long n)
227{
228 return __copy_from_user_inatomic(to, from, n);
229}
230
231#endif /* ARCH_HAS_NOCACHE_UACCESS */
232
233/*
234 * probe_kernel_read(): safely attempt to read from a location
235 * @dst: pointer to the buffer that shall take the data
236 * @src: address to read from
237 * @size: size of the data chunk
238 *
239 * Safely read from address @src to the buffer at @dst. If a kernel fault
240 * happens, handle that and return -EFAULT.
241 */
242extern long probe_kernel_read(void *dst, const void *src, size_t size);
243extern long __probe_kernel_read(void *dst, const void *src, size_t size);
244
245/*
246 * probe_kernel_write(): safely attempt to write to a location
247 * @dst: address to write to
248 * @src: pointer to the data that shall be written
249 * @size: size of the data chunk
250 *
251 * Safely write to address @dst from the buffer at @src. If a kernel fault
252 * happens, handle that and return -EFAULT.
253 */
254extern long notrace probe_kernel_write(void *dst, const void *src, size_t size);
255extern long notrace __probe_kernel_write(void *dst, const void *src, size_t size);
256
257extern long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count);
258
259/**
260 * probe_kernel_address(): safely attempt to read from a location
261 * @addr: address to read from
262 * @retval: read into this variable
263 *
264 * Returns 0 on success, or -EFAULT.
265 */
266#define probe_kernel_address(addr, retval) \
267 probe_kernel_read(&retval, addr, sizeof(retval))
268
269#ifndef user_access_begin
270#define user_access_begin() do { } while (0)
271#define user_access_end() do { } while (0)
272#define unsafe_get_user(x, ptr, err) do { if (unlikely(__get_user(x, ptr))) goto err; } while (0)
273#define unsafe_put_user(x, ptr, err) do { if (unlikely(__put_user(x, ptr))) goto err; } while (0)
274#endif
275
276#ifdef CONFIG_HARDENED_USERCOPY
277void usercopy_warn(const char *name, const char *detail, bool to_user,
278 unsigned long offset, unsigned long len);
279void __noreturn usercopy_abort(const char *name, const char *detail,
280 bool to_user, unsigned long offset,
281 unsigned long len);
282#endif
283
284#endif /* __LINUX_UACCESS_H__ */
285