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/nospec.h> 9 #include <linux/sched.h> 10 #include <linux/thread_info.h> 11 12 #include <asm/uaccess.h> 13 14 /* 15 * Architectures that support memory tagging (assigning tags to memory regions, 16 * embedding these tags into addresses that point to these memory regions, and 17 * checking that the memory and the pointer tags match on memory accesses) 18 * redefine this macro to strip tags from pointers. 19 * 20 * Passing down mm_struct allows to define untagging rules on per-process 21 * basis. 22 * 23 * It's defined as noop for architectures that don't support memory tagging. 24 */ 25 #ifndef untagged_addr 26 #define untagged_addr(addr) (addr) 27 #endif 28 29 #ifndef untagged_addr_remote 30 #define untagged_addr_remote(mm, addr) ({ \ 31 mmap_assert_locked(mm); \ 32 untagged_addr(addr); \ 33 }) 34 #endif 35 36 /* 37 * Architectures should provide two primitives (raw_copy_{to,from}_user()) 38 * and get rid of their private instances of copy_{to,from}_user() and 39 * __copy_{to,from}_user{,_inatomic}(). 40 * 41 * raw_copy_{to,from}_user(to, from, size) should copy up to size bytes and 42 * return the amount left to copy. They should assume that access_ok() has 43 * already been checked (and succeeded); they should *not* zero-pad anything. 44 * No KASAN or object size checks either - those belong here. 45 * 46 * Both of these functions should attempt to copy size bytes starting at from 47 * into the area starting at to. They must not fetch or store anything 48 * outside of those areas. Return value must be between 0 (everything 49 * copied successfully) and size (nothing copied). 50 * 51 * If raw_copy_{to,from}_user(to, from, size) returns N, size - N bytes starting 52 * at to must become equal to the bytes fetched from the corresponding area 53 * starting at from. All data past to + size - N must be left unmodified. 54 * 55 * If copying succeeds, the return value must be 0. If some data cannot be 56 * fetched, it is permitted to copy less than had been fetched; the only 57 * hard requirement is that not storing anything at all (i.e. returning size) 58 * should happen only when nothing could be copied. In other words, you don't 59 * have to squeeze as much as possible - it is allowed, but not necessary. 60 * 61 * For raw_copy_from_user() to always points to kernel memory and no faults 62 * on store should happen. Interpretation of from is affected by set_fs(). 63 * For raw_copy_to_user() it's the other way round. 64 * 65 * Both can be inlined - it's up to architectures whether it wants to bother 66 * with that. They should not be used directly; they are used to implement 67 * the 6 functions (copy_{to,from}_user(), __copy_{to,from}_user_inatomic()) 68 * that are used instead. Out of those, __... ones are inlined. Plain 69 * copy_{to,from}_user() might or might not be inlined. If you want them 70 * inlined, have asm/uaccess.h define INLINE_COPY_{TO,FROM}_USER. 71 * 72 * NOTE: only copy_from_user() zero-pads the destination in case of short copy. 73 * Neither __copy_from_user() nor __copy_from_user_inatomic() zero anything 74 * at all; their callers absolutely must check the return value. 75 * 76 * Biarch ones should also provide raw_copy_in_user() - similar to the above, 77 * but both source and destination are __user pointers (affected by set_fs() 78 * as usual) and both source and destination can trigger faults. 79 */ 80 81 static __always_inline __must_check unsigned long 82 __copy_from_user_inatomic(void *to, const void __user *from, unsigned long n) 83 { 84 unsigned long res; 85 86 instrument_copy_from_user_before(to, from, n); 87 check_object_size(to, n, false); 88 res = raw_copy_from_user(to, from, n); 89 instrument_copy_from_user_after(to, from, n, res); 90 return res; 91 } 92 93 static __always_inline __must_check unsigned long 94 __copy_from_user(void *to, const void __user *from, unsigned long n) 95 { 96 unsigned long res; 97 98 might_fault(); 99 instrument_copy_from_user_before(to, from, n); 100 if (should_fail_usercopy()) 101 return n; 102 check_object_size(to, n, false); 103 res = raw_copy_from_user(to, from, n); 104 instrument_copy_from_user_after(to, from, n, res); 105 return res; 106 } 107 108 /** 109 * __copy_to_user_inatomic: - Copy a block of data into user space, with less checking. 110 * @to: Destination address, in user space. 111 * @from: Source address, in kernel space. 112 * @n: Number of bytes to copy. 113 * 114 * Context: User context only. 115 * 116 * Copy data from kernel space to user space. Caller must check 117 * the specified block with access_ok() before calling this function. 118 * The caller should also make sure he pins the user space address 119 * so that we don't result in page fault and sleep. 120 */ 121 static __always_inline __must_check unsigned long 122 __copy_to_user_inatomic(void __user *to, const void *from, unsigned long n) 123 { 124 if (should_fail_usercopy()) 125 return n; 126 instrument_copy_to_user(to, from, n); 127 check_object_size(from, n, true); 128 return raw_copy_to_user(to, from, n); 129 } 130 131 static __always_inline __must_check unsigned long 132 __copy_to_user(void __user *to, const void *from, unsigned long n) 133 { 134 might_fault(); 135 if (should_fail_usercopy()) 136 return n; 137 instrument_copy_to_user(to, from, n); 138 check_object_size(from, n, true); 139 return raw_copy_to_user(to, from, n); 140 } 141 142 /* 143 * Architectures that #define INLINE_COPY_TO_USER use this function 144 * directly in the normal copy_to/from_user(), the other ones go 145 * through an extern _copy_to/from_user(), which expands the same code 146 * here. 147 * 148 * Rust code always uses the extern definition. 149 */ 150 static inline __must_check unsigned long 151 _inline_copy_from_user(void *to, const void __user *from, unsigned long n) 152 { 153 unsigned long res = n; 154 might_fault(); 155 if (!should_fail_usercopy() && likely(access_ok(from, n))) { 156 /* 157 * Ensure that bad access_ok() speculation will not 158 * lead to nasty side effects *after* the copy is 159 * finished: 160 */ 161 barrier_nospec(); 162 instrument_copy_from_user_before(to, from, n); 163 res = raw_copy_from_user(to, from, n); 164 instrument_copy_from_user_after(to, from, n, res); 165 } 166 if (unlikely(res)) 167 memset(to + (n - res), 0, res); 168 return res; 169 } 170 extern __must_check unsigned long 171 _copy_from_user(void *, const void __user *, unsigned long); 172 173 static inline __must_check unsigned long 174 _inline_copy_to_user(void __user *to, const void *from, unsigned long n) 175 { 176 might_fault(); 177 if (should_fail_usercopy()) 178 return n; 179 if (access_ok(to, n)) { 180 instrument_copy_to_user(to, from, n); 181 n = raw_copy_to_user(to, from, n); 182 } 183 return n; 184 } 185 extern __must_check unsigned long 186 _copy_to_user(void __user *, const void *, unsigned long); 187 188 static __always_inline unsigned long __must_check 189 copy_from_user(void *to, const void __user *from, unsigned long n) 190 { 191 if (!check_copy_size(to, n, false)) 192 return n; 193 #ifdef INLINE_COPY_FROM_USER 194 return _inline_copy_from_user(to, from, n); 195 #else 196 return _copy_from_user(to, from, n); 197 #endif 198 } 199 200 static __always_inline unsigned long __must_check 201 copy_to_user(void __user *to, const void *from, unsigned long n) 202 { 203 if (!check_copy_size(from, n, true)) 204 return n; 205 206 #ifdef INLINE_COPY_TO_USER 207 return _inline_copy_to_user(to, from, n); 208 #else 209 return _copy_to_user(to, from, n); 210 #endif 211 } 212 213 #ifndef copy_mc_to_kernel 214 /* 215 * Without arch opt-in this generic copy_mc_to_kernel() will not handle 216 * #MC (or arch equivalent) during source read. 217 */ 218 static inline unsigned long __must_check 219 copy_mc_to_kernel(void *dst, const void *src, size_t cnt) 220 { 221 memcpy(dst, src, cnt); 222 return 0; 223 } 224 #endif 225 226 static __always_inline void pagefault_disabled_inc(void) 227 { 228 current->pagefault_disabled++; 229 } 230 231 static __always_inline void pagefault_disabled_dec(void) 232 { 233 current->pagefault_disabled--; 234 } 235 236 /* 237 * These routines enable/disable the pagefault handler. If disabled, it will 238 * not take any locks and go straight to the fixup table. 239 * 240 * User access methods will not sleep when called from a pagefault_disabled() 241 * environment. 242 */ 243 static inline void pagefault_disable(void) 244 { 245 pagefault_disabled_inc(); 246 /* 247 * make sure to have issued the store before a pagefault 248 * can hit. 249 */ 250 barrier(); 251 } 252 253 static inline void pagefault_enable(void) 254 { 255 /* 256 * make sure to issue those last loads/stores before enabling 257 * the pagefault handler again. 258 */ 259 barrier(); 260 pagefault_disabled_dec(); 261 } 262 263 /* 264 * Is the pagefault handler disabled? If so, user access methods will not sleep. 265 */ 266 static inline bool pagefault_disabled(void) 267 { 268 return current->pagefault_disabled != 0; 269 } 270 271 /* 272 * The pagefault handler is in general disabled by pagefault_disable() or 273 * when in irq context (via in_atomic()). 274 * 275 * This function should only be used by the fault handlers. Other users should 276 * stick to pagefault_disabled(). 277 * Please NEVER use preempt_disable() to disable the fault handler. With 278 * !CONFIG_PREEMPT_COUNT, this is like a NOP. So the handler won't be disabled. 279 * in_atomic() will report different values based on !CONFIG_PREEMPT_COUNT. 280 */ 281 #define faulthandler_disabled() (pagefault_disabled() || in_atomic()) 282 283 #ifndef CONFIG_ARCH_HAS_SUBPAGE_FAULTS 284 285 /** 286 * probe_subpage_writeable: probe the user range for write faults at sub-page 287 * granularity (e.g. arm64 MTE) 288 * @uaddr: start of address range 289 * @size: size of address range 290 * 291 * Returns 0 on success, the number of bytes not probed on fault. 292 * 293 * It is expected that the caller checked for the write permission of each 294 * page in the range either by put_user() or GUP. The architecture port can 295 * implement a more efficient get_user() probing if the same sub-page faults 296 * are triggered by either a read or a write. 297 */ 298 static inline size_t probe_subpage_writeable(char __user *uaddr, size_t size) 299 { 300 return 0; 301 } 302 303 #endif /* CONFIG_ARCH_HAS_SUBPAGE_FAULTS */ 304 305 #ifndef ARCH_HAS_NOCACHE_UACCESS 306 307 static inline __must_check unsigned long 308 __copy_from_user_inatomic_nocache(void *to, const void __user *from, 309 unsigned long n) 310 { 311 return __copy_from_user_inatomic(to, from, n); 312 } 313 314 #endif /* ARCH_HAS_NOCACHE_UACCESS */ 315 316 extern __must_check int check_zeroed_user(const void __user *from, size_t size); 317 318 /** 319 * copy_struct_from_user: copy a struct from userspace 320 * @dst: Destination address, in kernel space. This buffer must be @ksize 321 * bytes long. 322 * @ksize: Size of @dst struct. 323 * @src: Source address, in userspace. 324 * @usize: (Alleged) size of @src struct. 325 * 326 * Copies a struct from userspace to kernel space, in a way that guarantees 327 * backwards-compatibility for struct syscall arguments (as long as future 328 * struct extensions are made such that all new fields are *appended* to the 329 * old struct, and zeroed-out new fields have the same meaning as the old 330 * struct). 331 * 332 * @ksize is just sizeof(*dst), and @usize should've been passed by userspace. 333 * The recommended usage is something like the following: 334 * 335 * SYSCALL_DEFINE2(foobar, const struct foo __user *, uarg, size_t, usize) 336 * { 337 * int err; 338 * struct foo karg = {}; 339 * 340 * if (usize > PAGE_SIZE) 341 * return -E2BIG; 342 * if (usize < FOO_SIZE_VER0) 343 * return -EINVAL; 344 * 345 * err = copy_struct_from_user(&karg, sizeof(karg), uarg, usize); 346 * if (err) 347 * return err; 348 * 349 * // ... 350 * } 351 * 352 * There are three cases to consider: 353 * * If @usize == @ksize, then it's copied verbatim. 354 * * If @usize < @ksize, then the userspace has passed an old struct to a 355 * newer kernel. The rest of the trailing bytes in @dst (@ksize - @usize) 356 * are to be zero-filled. 357 * * If @usize > @ksize, then the userspace has passed a new struct to an 358 * older kernel. The trailing bytes unknown to the kernel (@usize - @ksize) 359 * are checked to ensure they are zeroed, otherwise -E2BIG is returned. 360 * 361 * Returns (in all cases, some data may have been copied): 362 * * -E2BIG: (@usize > @ksize) and there are non-zero trailing bytes in @src. 363 * * -EFAULT: access to userspace failed. 364 */ 365 static __always_inline __must_check int 366 copy_struct_from_user(void *dst, size_t ksize, const void __user *src, 367 size_t usize) 368 { 369 size_t size = min(ksize, usize); 370 size_t rest = max(ksize, usize) - size; 371 372 /* Double check if ksize is larger than a known object size. */ 373 if (WARN_ON_ONCE(ksize > __builtin_object_size(dst, 1))) 374 return -E2BIG; 375 376 /* Deal with trailing bytes. */ 377 if (usize < ksize) { 378 memset(dst + size, 0, rest); 379 } else if (usize > ksize) { 380 int ret = check_zeroed_user(src + size, rest); 381 if (ret <= 0) 382 return ret ?: -E2BIG; 383 } 384 /* Copy the interoperable parts of the struct. */ 385 if (copy_from_user(dst, src, size)) 386 return -EFAULT; 387 return 0; 388 } 389 390 bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size); 391 392 long copy_from_kernel_nofault(void *dst, const void *src, size_t size); 393 long notrace copy_to_kernel_nofault(void *dst, const void *src, size_t size); 394 395 long copy_from_user_nofault(void *dst, const void __user *src, size_t size); 396 long notrace copy_to_user_nofault(void __user *dst, const void *src, 397 size_t size); 398 399 long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, 400 long count); 401 402 long strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr, 403 long count); 404 long strnlen_user_nofault(const void __user *unsafe_addr, long count); 405 406 #ifndef __get_kernel_nofault 407 #define __get_kernel_nofault(dst, src, type, label) \ 408 do { \ 409 type __user *p = (type __force __user *)(src); \ 410 type data; \ 411 if (__get_user(data, p)) \ 412 goto label; \ 413 *(type *)dst = data; \ 414 } while (0) 415 416 #define __put_kernel_nofault(dst, src, type, label) \ 417 do { \ 418 type __user *p = (type __force __user *)(dst); \ 419 type data = *(type *)src; \ 420 if (__put_user(data, p)) \ 421 goto label; \ 422 } while (0) 423 #endif 424 425 /** 426 * get_kernel_nofault(): safely attempt to read from a location 427 * @val: read into this variable 428 * @ptr: address to read from 429 * 430 * Returns 0 on success, or -EFAULT. 431 */ 432 #define get_kernel_nofault(val, ptr) ({ \ 433 const typeof(val) *__gk_ptr = (ptr); \ 434 copy_from_kernel_nofault(&(val), __gk_ptr, sizeof(val));\ 435 }) 436 437 #ifndef user_access_begin 438 #define user_access_begin(ptr,len) access_ok(ptr, len) 439 #define user_access_end() do { } while (0) 440 #define unsafe_op_wrap(op, err) do { if (unlikely(op)) goto err; } while (0) 441 #define unsafe_get_user(x,p,e) unsafe_op_wrap(__get_user(x,p),e) 442 #define unsafe_put_user(x,p,e) unsafe_op_wrap(__put_user(x,p),e) 443 #define unsafe_copy_to_user(d,s,l,e) unsafe_op_wrap(__copy_to_user(d,s,l),e) 444 #define unsafe_copy_from_user(d,s,l,e) unsafe_op_wrap(__copy_from_user(d,s,l),e) 445 static inline unsigned long user_access_save(void) { return 0UL; } 446 static inline void user_access_restore(unsigned long flags) { } 447 #endif 448 #ifndef user_write_access_begin 449 #define user_write_access_begin user_access_begin 450 #define user_write_access_end user_access_end 451 #endif 452 #ifndef user_read_access_begin 453 #define user_read_access_begin user_access_begin 454 #define user_read_access_end user_access_end 455 #endif 456 457 #ifdef CONFIG_HARDENED_USERCOPY 458 void __noreturn usercopy_abort(const char *name, const char *detail, 459 bool to_user, unsigned long offset, 460 unsigned long len); 461 #endif 462 463 #endif /* __LINUX_UACCESS_H__ */ 464