1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __LINUX_UACCESS_H__
3 #define __LINUX_UACCESS_H__
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>
11 #include <asm/uaccess.h>
15 * Force the uaccess routines to be wired up for actual userspace access,
16 * overriding any possible set_fs(KERNEL_DS) still lingering around. Undone
17 * using force_uaccess_end below.
19 static inline mm_segment_t force_uaccess_begin(void)
21 mm_segment_t fs = get_fs();
27 static inline void force_uaccess_end(mm_segment_t oldfs)
31 #else /* CONFIG_SET_FS */
36 #define uaccess_kernel() (false)
37 #define user_addr_max() (TASK_SIZE_MAX)
39 static inline mm_segment_t force_uaccess_begin(void)
41 return (mm_segment_t) { };
44 static inline void force_uaccess_end(mm_segment_t oldfs)
47 #endif /* CONFIG_SET_FS */
50 * Architectures should provide two primitives (raw_copy_{to,from}_user())
51 * and get rid of their private instances of copy_{to,from}_user() and
52 * __copy_{to,from}_user{,_inatomic}().
54 * raw_copy_{to,from}_user(to, from, size) should copy up to size bytes and
55 * return the amount left to copy. They should assume that access_ok() has
56 * already been checked (and succeeded); they should *not* zero-pad anything.
57 * No KASAN or object size checks either - those belong here.
59 * Both of these functions should attempt to copy size bytes starting at from
60 * into the area starting at to. They must not fetch or store anything
61 * outside of those areas. Return value must be between 0 (everything
62 * copied successfully) and size (nothing copied).
64 * If raw_copy_{to,from}_user(to, from, size) returns N, size - N bytes starting
65 * at to must become equal to the bytes fetched from the corresponding area
66 * starting at from. All data past to + size - N must be left unmodified.
68 * If copying succeeds, the return value must be 0. If some data cannot be
69 * fetched, it is permitted to copy less than had been fetched; the only
70 * hard requirement is that not storing anything at all (i.e. returning size)
71 * should happen only when nothing could be copied. In other words, you don't
72 * have to squeeze as much as possible - it is allowed, but not necessary.
74 * For raw_copy_from_user() to always points to kernel memory and no faults
75 * on store should happen. Interpretation of from is affected by set_fs().
76 * For raw_copy_to_user() it's the other way round.
78 * Both can be inlined - it's up to architectures whether it wants to bother
79 * with that. They should not be used directly; they are used to implement
80 * the 6 functions (copy_{to,from}_user(), __copy_{to,from}_user_inatomic())
81 * that are used instead. Out of those, __... ones are inlined. Plain
82 * copy_{to,from}_user() might or might not be inlined. If you want them
83 * inlined, have asm/uaccess.h define INLINE_COPY_{TO,FROM}_USER.
85 * NOTE: only copy_from_user() zero-pads the destination in case of short copy.
86 * Neither __copy_from_user() nor __copy_from_user_inatomic() zero anything
87 * at all; their callers absolutely must check the return value.
89 * Biarch ones should also provide raw_copy_in_user() - similar to the above,
90 * but both source and destination are __user pointers (affected by set_fs()
91 * as usual) and both source and destination can trigger faults.
94 static __always_inline __must_check unsigned long
95 __copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
97 instrument_copy_from_user(to, from, n);
98 check_object_size(to, n, false);
99 return raw_copy_from_user(to, from, n);
102 static __always_inline __must_check unsigned long
103 __copy_from_user(void *to, const void __user *from, unsigned long n)
106 if (should_fail_usercopy())
108 instrument_copy_from_user(to, from, n);
109 check_object_size(to, n, false);
110 return raw_copy_from_user(to, from, n);
114 * __copy_to_user_inatomic: - Copy a block of data into user space, with less checking.
115 * @to: Destination address, in user space.
116 * @from: Source address, in kernel space.
117 * @n: Number of bytes to copy.
119 * Context: User context only.
121 * Copy data from kernel space to user space. Caller must check
122 * the specified block with access_ok() before calling this function.
123 * The caller should also make sure he pins the user space address
124 * so that we don't result in page fault and sleep.
126 static __always_inline __must_check unsigned long
127 __copy_to_user_inatomic(void __user *to, const void *from, unsigned long n)
129 if (should_fail_usercopy())
131 instrument_copy_to_user(to, from, n);
132 check_object_size(from, n, true);
133 return raw_copy_to_user(to, from, n);
136 static __always_inline __must_check unsigned long
137 __copy_to_user(void __user *to, const void *from, unsigned long n)
140 if (should_fail_usercopy())
142 instrument_copy_to_user(to, from, n);
143 check_object_size(from, n, true);
144 return raw_copy_to_user(to, from, n);
147 #ifdef INLINE_COPY_FROM_USER
148 static inline __must_check unsigned long
149 _copy_from_user(void *to, const void __user *from, unsigned long n)
151 unsigned long res = n;
153 if (!should_fail_usercopy() && likely(access_ok(from, n))) {
154 instrument_copy_from_user(to, from, n);
155 res = raw_copy_from_user(to, from, n);
158 memset(to + (n - res), 0, res);
162 extern __must_check unsigned long
163 _copy_from_user(void *, const void __user *, unsigned long);
166 #ifdef INLINE_COPY_TO_USER
167 static inline __must_check unsigned long
168 _copy_to_user(void __user *to, const void *from, unsigned long n)
171 if (should_fail_usercopy())
173 if (access_ok(to, n)) {
174 instrument_copy_to_user(to, from, n);
175 n = raw_copy_to_user(to, from, n);
180 extern __must_check unsigned long
181 _copy_to_user(void __user *, const void *, unsigned long);
184 static __always_inline unsigned long __must_check
185 copy_from_user(void *to, const void __user *from, unsigned long n)
187 if (likely(check_copy_size(to, n, false)))
188 n = _copy_from_user(to, from, n);
192 static __always_inline unsigned long __must_check
193 copy_to_user(void __user *to, const void *from, unsigned long n)
195 if (likely(check_copy_size(from, n, true)))
196 n = _copy_to_user(to, from, n);
200 static __always_inline unsigned long __must_check
201 copy_in_user(void __user *to, const void __user *from, unsigned long n)
204 if (access_ok(to, n) && access_ok(from, n))
205 n = raw_copy_in_user(to, from, n);
210 #ifndef copy_mc_to_kernel
212 * Without arch opt-in this generic copy_mc_to_kernel() will not handle
213 * #MC (or arch equivalent) during source read.
215 static inline unsigned long __must_check
216 copy_mc_to_kernel(void *dst, const void *src, size_t cnt)
218 memcpy(dst, src, cnt);
223 static __always_inline void pagefault_disabled_inc(void)
225 current->pagefault_disabled++;
228 static __always_inline void pagefault_disabled_dec(void)
230 current->pagefault_disabled--;
234 * These routines enable/disable the pagefault handler. If disabled, it will
235 * not take any locks and go straight to the fixup table.
237 * User access methods will not sleep when called from a pagefault_disabled()
240 static inline void pagefault_disable(void)
242 pagefault_disabled_inc();
244 * make sure to have issued the store before a pagefault
250 static inline void pagefault_enable(void)
253 * make sure to issue those last loads/stores before enabling
254 * the pagefault handler again.
257 pagefault_disabled_dec();
261 * Is the pagefault handler disabled? If so, user access methods will not sleep.
263 static inline bool pagefault_disabled(void)
265 return current->pagefault_disabled != 0;
269 * The pagefault handler is in general disabled by pagefault_disable() or
270 * when in irq context (via in_atomic()).
272 * This function should only be used by the fault handlers. Other users should
273 * stick to pagefault_disabled().
274 * Please NEVER use preempt_disable() to disable the fault handler. With
275 * !CONFIG_PREEMPT_COUNT, this is like a NOP. So the handler won't be disabled.
276 * in_atomic() will report different values based on !CONFIG_PREEMPT_COUNT.
278 #define faulthandler_disabled() (pagefault_disabled() || in_atomic())
280 #ifndef ARCH_HAS_NOCACHE_UACCESS
282 static inline __must_check unsigned long
283 __copy_from_user_inatomic_nocache(void *to, const void __user *from,
286 return __copy_from_user_inatomic(to, from, n);
289 #endif /* ARCH_HAS_NOCACHE_UACCESS */
291 extern __must_check int check_zeroed_user(const void __user *from, size_t size);
294 * copy_struct_from_user: copy a struct from userspace
295 * @dst: Destination address, in kernel space. This buffer must be @ksize
297 * @ksize: Size of @dst struct.
298 * @src: Source address, in userspace.
299 * @usize: (Alleged) size of @src struct.
301 * Copies a struct from userspace to kernel space, in a way that guarantees
302 * backwards-compatibility for struct syscall arguments (as long as future
303 * struct extensions are made such that all new fields are *appended* to the
304 * old struct, and zeroed-out new fields have the same meaning as the old
307 * @ksize is just sizeof(*dst), and @usize should've been passed by userspace.
308 * The recommended usage is something like the following:
310 * SYSCALL_DEFINE2(foobar, const struct foo __user *, uarg, size_t, usize)
313 * struct foo karg = {};
315 * if (usize > PAGE_SIZE)
317 * if (usize < FOO_SIZE_VER0)
320 * err = copy_struct_from_user(&karg, sizeof(karg), uarg, usize);
327 * There are three cases to consider:
328 * * If @usize == @ksize, then it's copied verbatim.
329 * * If @usize < @ksize, then the userspace has passed an old struct to a
330 * newer kernel. The rest of the trailing bytes in @dst (@ksize - @usize)
331 * are to be zero-filled.
332 * * If @usize > @ksize, then the userspace has passed a new struct to an
333 * older kernel. The trailing bytes unknown to the kernel (@usize - @ksize)
334 * are checked to ensure they are zeroed, otherwise -E2BIG is returned.
336 * Returns (in all cases, some data may have been copied):
337 * * -E2BIG: (@usize > @ksize) and there are non-zero trailing bytes in @src.
338 * * -EFAULT: access to userspace failed.
340 static __always_inline __must_check int
341 copy_struct_from_user(void *dst, size_t ksize, const void __user *src,
344 size_t size = min(ksize, usize);
345 size_t rest = max(ksize, usize) - size;
347 /* Deal with trailing bytes. */
349 memset(dst + size, 0, rest);
350 } else if (usize > ksize) {
351 int ret = check_zeroed_user(src + size, rest);
353 return ret ?: -E2BIG;
355 /* Copy the interoperable parts of the struct. */
356 if (copy_from_user(dst, src, size))
361 bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size);
363 long copy_from_kernel_nofault(void *dst, const void *src, size_t size);
364 long notrace copy_to_kernel_nofault(void *dst, const void *src, size_t size);
366 long copy_from_user_nofault(void *dst, const void __user *src, size_t size);
367 long notrace copy_to_user_nofault(void __user *dst, const void *src,
370 long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr,
373 long strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr,
375 long strnlen_user_nofault(const void __user *unsafe_addr, long count);
378 * get_kernel_nofault(): safely attempt to read from a location
379 * @val: read into this variable
380 * @ptr: address to read from
382 * Returns 0 on success, or -EFAULT.
384 #define get_kernel_nofault(val, ptr) ({ \
385 const typeof(val) *__gk_ptr = (ptr); \
386 copy_from_kernel_nofault(&(val), __gk_ptr, sizeof(val));\
389 #ifndef user_access_begin
390 #define user_access_begin(ptr,len) access_ok(ptr, len)
391 #define user_access_end() do { } while (0)
392 #define unsafe_op_wrap(op, err) do { if (unlikely(op)) goto err; } while (0)
393 #define unsafe_get_user(x,p,e) unsafe_op_wrap(__get_user(x,p),e)
394 #define unsafe_put_user(x,p,e) unsafe_op_wrap(__put_user(x,p),e)
395 #define unsafe_copy_to_user(d,s,l,e) unsafe_op_wrap(__copy_to_user(d,s,l),e)
396 static inline unsigned long user_access_save(void) { return 0UL; }
397 static inline void user_access_restore(unsigned long flags) { }
399 #ifndef user_write_access_begin
400 #define user_write_access_begin user_access_begin
401 #define user_write_access_end user_access_end
403 #ifndef user_read_access_begin
404 #define user_read_access_begin user_access_begin
405 #define user_read_access_end user_access_end
408 #ifdef CONFIG_HARDENED_USERCOPY
409 void usercopy_warn(const char *name, const char *detail, bool to_user,
410 unsigned long offset, unsigned long len);
411 void __noreturn usercopy_abort(const char *name, const char *detail,
412 bool to_user, unsigned long offset,
416 #endif /* __LINUX_UACCESS_H__ */