1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __LINUX_UACCESS_H__
3 #define __LINUX_UACCESS_H__
5 #include <linux/instrumented.h>
6 #include <linux/sched.h>
7 #include <linux/thread_info.h>
9 #include <asm/uaccess.h>
12 * Force the uaccess routines to be wired up for actual userspace access,
13 * overriding any possible set_fs(KERNEL_DS) still lingering around. Undone
14 * using force_uaccess_end below.
16 static inline mm_segment_t force_uaccess_begin(void)
18 mm_segment_t fs = get_fs();
24 static inline void force_uaccess_end(mm_segment_t oldfs)
30 * Architectures should provide two primitives (raw_copy_{to,from}_user())
31 * and get rid of their private instances of copy_{to,from}_user() and
32 * __copy_{to,from}_user{,_inatomic}().
34 * raw_copy_{to,from}_user(to, from, size) should copy up to size bytes and
35 * return the amount left to copy. They should assume that access_ok() has
36 * already been checked (and succeeded); they should *not* zero-pad anything.
37 * No KASAN or object size checks either - those belong here.
39 * Both of these functions should attempt to copy size bytes starting at from
40 * into the area starting at to. They must not fetch or store anything
41 * outside of those areas. Return value must be between 0 (everything
42 * copied successfully) and size (nothing copied).
44 * If raw_copy_{to,from}_user(to, from, size) returns N, size - N bytes starting
45 * at to must become equal to the bytes fetched from the corresponding area
46 * starting at from. All data past to + size - N must be left unmodified.
48 * If copying succeeds, the return value must be 0. If some data cannot be
49 * fetched, it is permitted to copy less than had been fetched; the only
50 * hard requirement is that not storing anything at all (i.e. returning size)
51 * should happen only when nothing could be copied. In other words, you don't
52 * have to squeeze as much as possible - it is allowed, but not necessary.
54 * For raw_copy_from_user() to always points to kernel memory and no faults
55 * on store should happen. Interpretation of from is affected by set_fs().
56 * For raw_copy_to_user() it's the other way round.
58 * Both can be inlined - it's up to architectures whether it wants to bother
59 * with that. They should not be used directly; they are used to implement
60 * the 6 functions (copy_{to,from}_user(), __copy_{to,from}_user_inatomic())
61 * that are used instead. Out of those, __... ones are inlined. Plain
62 * copy_{to,from}_user() might or might not be inlined. If you want them
63 * inlined, have asm/uaccess.h define INLINE_COPY_{TO,FROM}_USER.
65 * NOTE: only copy_from_user() zero-pads the destination in case of short copy.
66 * Neither __copy_from_user() nor __copy_from_user_inatomic() zero anything
67 * at all; their callers absolutely must check the return value.
69 * Biarch ones should also provide raw_copy_in_user() - similar to the above,
70 * but both source and destination are __user pointers (affected by set_fs()
71 * as usual) and both source and destination can trigger faults.
74 static __always_inline __must_check unsigned long
75 __copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
77 instrument_copy_from_user(to, from, n);
78 check_object_size(to, n, false);
79 return raw_copy_from_user(to, from, n);
82 static __always_inline __must_check unsigned long
83 __copy_from_user(void *to, const void __user *from, unsigned long n)
86 instrument_copy_from_user(to, from, n);
87 check_object_size(to, n, false);
88 return raw_copy_from_user(to, from, n);
92 * __copy_to_user_inatomic: - Copy a block of data into user space, with less checking.
93 * @to: Destination address, in user space.
94 * @from: Source address, in kernel space.
95 * @n: Number of bytes to copy.
97 * Context: User context only.
99 * Copy data from kernel space to user space. Caller must check
100 * the specified block with access_ok() before calling this function.
101 * The caller should also make sure he pins the user space address
102 * so that we don't result in page fault and sleep.
104 static __always_inline __must_check unsigned long
105 __copy_to_user_inatomic(void __user *to, const void *from, unsigned long n)
107 instrument_copy_to_user(to, from, n);
108 check_object_size(from, n, true);
109 return raw_copy_to_user(to, from, n);
112 static __always_inline __must_check unsigned long
113 __copy_to_user(void __user *to, const void *from, unsigned long n)
116 instrument_copy_to_user(to, from, n);
117 check_object_size(from, n, true);
118 return raw_copy_to_user(to, from, n);
121 #ifdef INLINE_COPY_FROM_USER
122 static inline __must_check unsigned long
123 _copy_from_user(void *to, const void __user *from, unsigned long n)
125 unsigned long res = n;
127 if (likely(access_ok(from, n))) {
128 instrument_copy_from_user(to, from, n);
129 res = raw_copy_from_user(to, from, n);
132 memset(to + (n - res), 0, res);
136 extern __must_check unsigned long
137 _copy_from_user(void *, const void __user *, unsigned long);
140 #ifdef INLINE_COPY_TO_USER
141 static inline __must_check unsigned long
142 _copy_to_user(void __user *to, const void *from, unsigned long n)
145 if (access_ok(to, n)) {
146 instrument_copy_to_user(to, from, n);
147 n = raw_copy_to_user(to, from, n);
152 extern __must_check unsigned long
153 _copy_to_user(void __user *, const void *, unsigned long);
156 static __always_inline unsigned long __must_check
157 copy_from_user(void *to, const void __user *from, unsigned long n)
159 if (likely(check_copy_size(to, n, false)))
160 n = _copy_from_user(to, from, n);
164 static __always_inline unsigned long __must_check
165 copy_to_user(void __user *to, const void *from, unsigned long n)
167 if (likely(check_copy_size(from, n, true)))
168 n = _copy_to_user(to, from, n);
172 static __always_inline unsigned long __must_check
173 copy_in_user(void __user *to, const void __user *from, unsigned long n)
176 if (access_ok(to, n) && access_ok(from, n))
177 n = raw_copy_in_user(to, from, n);
182 static __always_inline void pagefault_disabled_inc(void)
184 current->pagefault_disabled++;
187 static __always_inline void pagefault_disabled_dec(void)
189 current->pagefault_disabled--;
193 * These routines enable/disable the pagefault handler. If disabled, it will
194 * not take any locks and go straight to the fixup table.
196 * User access methods will not sleep when called from a pagefault_disabled()
199 static inline void pagefault_disable(void)
201 pagefault_disabled_inc();
203 * make sure to have issued the store before a pagefault
209 static inline void pagefault_enable(void)
212 * make sure to issue those last loads/stores before enabling
213 * the pagefault handler again.
216 pagefault_disabled_dec();
220 * Is the pagefault handler disabled? If so, user access methods will not sleep.
222 static inline bool pagefault_disabled(void)
224 return current->pagefault_disabled != 0;
228 * The pagefault handler is in general disabled by pagefault_disable() or
229 * when in irq context (via in_atomic()).
231 * This function should only be used by the fault handlers. Other users should
232 * stick to pagefault_disabled().
233 * Please NEVER use preempt_disable() to disable the fault handler. With
234 * !CONFIG_PREEMPT_COUNT, this is like a NOP. So the handler won't be disabled.
235 * in_atomic() will report different values based on !CONFIG_PREEMPT_COUNT.
237 #define faulthandler_disabled() (pagefault_disabled() || in_atomic())
239 #ifndef ARCH_HAS_NOCACHE_UACCESS
241 static inline __must_check unsigned long
242 __copy_from_user_inatomic_nocache(void *to, const void __user *from,
245 return __copy_from_user_inatomic(to, from, n);
248 #endif /* ARCH_HAS_NOCACHE_UACCESS */
250 extern __must_check int check_zeroed_user(const void __user *from, size_t size);
253 * copy_struct_from_user: copy a struct from userspace
254 * @dst: Destination address, in kernel space. This buffer must be @ksize
256 * @ksize: Size of @dst struct.
257 * @src: Source address, in userspace.
258 * @usize: (Alleged) size of @src struct.
260 * Copies a struct from userspace to kernel space, in a way that guarantees
261 * backwards-compatibility for struct syscall arguments (as long as future
262 * struct extensions are made such that all new fields are *appended* to the
263 * old struct, and zeroed-out new fields have the same meaning as the old
266 * @ksize is just sizeof(*dst), and @usize should've been passed by userspace.
267 * The recommended usage is something like the following:
269 * SYSCALL_DEFINE2(foobar, const struct foo __user *, uarg, size_t, usize)
272 * struct foo karg = {};
274 * if (usize > PAGE_SIZE)
276 * if (usize < FOO_SIZE_VER0)
279 * err = copy_struct_from_user(&karg, sizeof(karg), uarg, usize);
286 * There are three cases to consider:
287 * * If @usize == @ksize, then it's copied verbatim.
288 * * If @usize < @ksize, then the userspace has passed an old struct to a
289 * newer kernel. The rest of the trailing bytes in @dst (@ksize - @usize)
290 * are to be zero-filled.
291 * * If @usize > @ksize, then the userspace has passed a new struct to an
292 * older kernel. The trailing bytes unknown to the kernel (@usize - @ksize)
293 * are checked to ensure they are zeroed, otherwise -E2BIG is returned.
295 * Returns (in all cases, some data may have been copied):
296 * * -E2BIG: (@usize > @ksize) and there are non-zero trailing bytes in @src.
297 * * -EFAULT: access to userspace failed.
299 static __always_inline __must_check int
300 copy_struct_from_user(void *dst, size_t ksize, const void __user *src,
303 size_t size = min(ksize, usize);
304 size_t rest = max(ksize, usize) - size;
306 /* Deal with trailing bytes. */
308 memset(dst + size, 0, rest);
309 } else if (usize > ksize) {
310 int ret = check_zeroed_user(src + size, rest);
312 return ret ?: -E2BIG;
314 /* Copy the interoperable parts of the struct. */
315 if (copy_from_user(dst, src, size))
320 bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size);
322 long copy_from_kernel_nofault(void *dst, const void *src, size_t size);
323 long notrace copy_to_kernel_nofault(void *dst, const void *src, size_t size);
325 long copy_from_user_nofault(void *dst, const void __user *src, size_t size);
326 long notrace copy_to_user_nofault(void __user *dst, const void *src,
329 long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr,
332 long strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr,
334 long strnlen_user_nofault(const void __user *unsafe_addr, long count);
337 * get_kernel_nofault(): safely attempt to read from a location
338 * @val: read into this variable
339 * @ptr: address to read from
341 * Returns 0 on success, or -EFAULT.
343 #define get_kernel_nofault(val, ptr) ({ \
344 const typeof(val) *__gk_ptr = (ptr); \
345 copy_from_kernel_nofault(&(val), __gk_ptr, sizeof(val));\
348 #ifndef user_access_begin
349 #define user_access_begin(ptr,len) access_ok(ptr, len)
350 #define user_access_end() do { } while (0)
351 #define unsafe_op_wrap(op, err) do { if (unlikely(op)) goto err; } while (0)
352 #define unsafe_get_user(x,p,e) unsafe_op_wrap(__get_user(x,p),e)
353 #define unsafe_put_user(x,p,e) unsafe_op_wrap(__put_user(x,p),e)
354 #define unsafe_copy_to_user(d,s,l,e) unsafe_op_wrap(__copy_to_user(d,s,l),e)
355 static inline unsigned long user_access_save(void) { return 0UL; }
356 static inline void user_access_restore(unsigned long flags) { }
358 #ifndef user_write_access_begin
359 #define user_write_access_begin user_access_begin
360 #define user_write_access_end user_access_end
362 #ifndef user_read_access_begin
363 #define user_read_access_begin user_access_begin
364 #define user_read_access_end user_access_end
367 #ifdef CONFIG_HARDENED_USERCOPY
368 void usercopy_warn(const char *name, const char *detail, bool to_user,
369 unsigned long offset, unsigned long len);
370 void __noreturn usercopy_abort(const char *name, const char *detail,
371 bool to_user, unsigned long offset,
375 #endif /* __LINUX_UACCESS_H__ */