1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _LINUX_FORTIFY_STRING_H_ 3 #define _LINUX_FORTIFY_STRING_H_ 4 5 #include <linux/bitfield.h> 6 #include <linux/bug.h> 7 #include <linux/const.h> 8 #include <linux/limits.h> 9 10 #define __FORTIFY_INLINE extern __always_inline __gnu_inline __overloadable 11 #define __RENAME(x) __asm__(#x) 12 13 #define FORTIFY_REASON_DIR(r) FIELD_GET(BIT(0), r) 14 #define FORTIFY_REASON_FUNC(r) FIELD_GET(GENMASK(7, 1), r) 15 #define FORTIFY_REASON(func, write) (FIELD_PREP(BIT(0), write) | \ 16 FIELD_PREP(GENMASK(7, 1), func)) 17 18 #define fortify_panic(func, write) \ 19 __fortify_panic(FORTIFY_REASON(func, write)) 20 21 #define FORTIFY_READ 0 22 #define FORTIFY_WRITE 1 23 24 #define EACH_FORTIFY_FUNC(macro) \ 25 macro(strncpy), \ 26 macro(strnlen), \ 27 macro(strlen), \ 28 macro(strscpy), \ 29 macro(strlcat), \ 30 macro(strcat), \ 31 macro(strncat), \ 32 macro(memset), \ 33 macro(memcpy), \ 34 macro(memmove), \ 35 macro(memscan), \ 36 macro(memcmp), \ 37 macro(memchr), \ 38 macro(memchr_inv), \ 39 macro(kmemdup), \ 40 macro(strcpy), \ 41 macro(UNKNOWN), 42 43 #define MAKE_FORTIFY_FUNC(func) FORTIFY_FUNC_##func 44 45 enum fortify_func { 46 EACH_FORTIFY_FUNC(MAKE_FORTIFY_FUNC) 47 }; 48 49 void __fortify_report(const u8 reason); 50 void __fortify_panic(const u8 reason) __cold __noreturn; 51 void __read_overflow(void) __compiletime_error("detected read beyond size of object (1st parameter)"); 52 void __read_overflow2(void) __compiletime_error("detected read beyond size of object (2nd parameter)"); 53 void __read_overflow2_field(size_t avail, size_t wanted) __compiletime_warning("detected read beyond size of field (2nd parameter); maybe use struct_group()?"); 54 void __write_overflow(void) __compiletime_error("detected write beyond size of object (1st parameter)"); 55 void __write_overflow_field(size_t avail, size_t wanted) __compiletime_warning("detected write beyond size of field (1st parameter); maybe use struct_group()?"); 56 57 #define __compiletime_strlen(p) \ 58 ({ \ 59 char *__p = (char *)(p); \ 60 size_t __ret = SIZE_MAX; \ 61 const size_t __p_size = __member_size(p); \ 62 if (__p_size != SIZE_MAX && \ 63 __builtin_constant_p(*__p)) { \ 64 size_t __p_len = __p_size - 1; \ 65 if (__builtin_constant_p(__p[__p_len]) && \ 66 __p[__p_len] == '\0') \ 67 __ret = __builtin_strlen(__p); \ 68 } \ 69 __ret; \ 70 }) 71 72 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS) 73 extern void *__underlying_memchr(const void *p, int c, __kernel_size_t size) __RENAME(memchr); 74 extern int __underlying_memcmp(const void *p, const void *q, __kernel_size_t size) __RENAME(memcmp); 75 extern void *__underlying_memcpy(void *p, const void *q, __kernel_size_t size) __RENAME(memcpy); 76 extern void *__underlying_memmove(void *p, const void *q, __kernel_size_t size) __RENAME(memmove); 77 extern void *__underlying_memset(void *p, int c, __kernel_size_t size) __RENAME(memset); 78 extern char *__underlying_strcat(char *p, const char *q) __RENAME(strcat); 79 extern char *__underlying_strcpy(char *p, const char *q) __RENAME(strcpy); 80 extern __kernel_size_t __underlying_strlen(const char *p) __RENAME(strlen); 81 extern char *__underlying_strncat(char *p, const char *q, __kernel_size_t count) __RENAME(strncat); 82 extern char *__underlying_strncpy(char *p, const char *q, __kernel_size_t size) __RENAME(strncpy); 83 #else 84 85 #if defined(__SANITIZE_MEMORY__) 86 /* 87 * For KMSAN builds all memcpy/memset/memmove calls should be replaced by the 88 * corresponding __msan_XXX functions. 89 */ 90 #include <linux/kmsan_string.h> 91 #define __underlying_memcpy __msan_memcpy 92 #define __underlying_memmove __msan_memmove 93 #define __underlying_memset __msan_memset 94 #else 95 #define __underlying_memcpy __builtin_memcpy 96 #define __underlying_memmove __builtin_memmove 97 #define __underlying_memset __builtin_memset 98 #endif 99 100 #define __underlying_memchr __builtin_memchr 101 #define __underlying_memcmp __builtin_memcmp 102 #define __underlying_strcat __builtin_strcat 103 #define __underlying_strcpy __builtin_strcpy 104 #define __underlying_strlen __builtin_strlen 105 #define __underlying_strncat __builtin_strncat 106 #define __underlying_strncpy __builtin_strncpy 107 #endif 108 109 /** 110 * unsafe_memcpy - memcpy implementation with no FORTIFY bounds checking 111 * 112 * @dst: Destination memory address to write to 113 * @src: Source memory address to read from 114 * @bytes: How many bytes to write to @dst from @src 115 * @justification: Free-form text or comment describing why the use is needed 116 * 117 * This should be used for corner cases where the compiler cannot do the 118 * right thing, or during transitions between APIs, etc. It should be used 119 * very rarely, and includes a place for justification detailing where bounds 120 * checking has happened, and why existing solutions cannot be employed. 121 */ 122 #define unsafe_memcpy(dst, src, bytes, justification) \ 123 __underlying_memcpy(dst, src, bytes) 124 125 /* 126 * Clang's use of __builtin_*object_size() within inlines needs hinting via 127 * __pass_*object_size(). The preference is to only ever use type 1 (member 128 * size, rather than struct size), but there remain some stragglers using 129 * type 0 that will be converted in the future. 130 */ 131 #if __has_builtin(__builtin_dynamic_object_size) 132 #define POS __pass_dynamic_object_size(1) 133 #define POS0 __pass_dynamic_object_size(0) 134 #else 135 #define POS __pass_object_size(1) 136 #define POS0 __pass_object_size(0) 137 #endif 138 139 #define __compiletime_lessthan(bounds, length) ( \ 140 __builtin_constant_p((bounds) < (length)) && \ 141 (bounds) < (length) \ 142 ) 143 144 /** 145 * strncpy - Copy a string to memory with non-guaranteed NUL padding 146 * 147 * @p: pointer to destination of copy 148 * @q: pointer to NUL-terminated source string to copy 149 * @size: bytes to write at @p 150 * 151 * If strlen(@q) >= @size, the copy of @q will stop after @size bytes, 152 * and @p will NOT be NUL-terminated 153 * 154 * If strlen(@q) < @size, following the copy of @q, trailing NUL bytes 155 * will be written to @p until @size total bytes have been written. 156 * 157 * Do not use this function. While FORTIFY_SOURCE tries to avoid 158 * over-reads of @q, it cannot defend against writing unterminated 159 * results to @p. Using strncpy() remains ambiguous and fragile. 160 * Instead, please choose an alternative, so that the expectation 161 * of @p's contents is unambiguous: 162 * 163 * +--------------------+--------------------+------------+ 164 * | **p** needs to be: | padded to **size** | not padded | 165 * +====================+====================+============+ 166 * | NUL-terminated | strscpy_pad() | strscpy() | 167 * +--------------------+--------------------+------------+ 168 * | not NUL-terminated | strtomem_pad() | strtomem() | 169 * +--------------------+--------------------+------------+ 170 * 171 * Note strscpy*()'s differing return values for detecting truncation, 172 * and strtomem*()'s expectation that the destination is marked with 173 * __nonstring when it is a character array. 174 * 175 */ 176 __FORTIFY_INLINE __diagnose_as(__builtin_strncpy, 1, 2, 3) 177 char *strncpy(char * const POS p, const char *q, __kernel_size_t size) 178 { 179 const size_t p_size = __member_size(p); 180 181 if (__compiletime_lessthan(p_size, size)) 182 __write_overflow(); 183 if (p_size < size) 184 fortify_panic(FORTIFY_FUNC_strncpy, FORTIFY_WRITE); 185 return __underlying_strncpy(p, q, size); 186 } 187 188 extern __kernel_size_t __real_strnlen(const char *, __kernel_size_t) __RENAME(strnlen); 189 /** 190 * strnlen - Return bounded count of characters in a NUL-terminated string 191 * 192 * @p: pointer to NUL-terminated string to count. 193 * @maxlen: maximum number of characters to count. 194 * 195 * Returns number of characters in @p (NOT including the final NUL), or 196 * @maxlen, if no NUL has been found up to there. 197 * 198 */ 199 __FORTIFY_INLINE __kernel_size_t strnlen(const char * const POS p, __kernel_size_t maxlen) 200 { 201 const size_t p_size = __member_size(p); 202 const size_t p_len = __compiletime_strlen(p); 203 size_t ret; 204 205 /* We can take compile-time actions when maxlen is const. */ 206 if (__builtin_constant_p(maxlen) && p_len != SIZE_MAX) { 207 /* If p is const, we can use its compile-time-known len. */ 208 if (maxlen >= p_size) 209 return p_len; 210 } 211 212 /* Do not check characters beyond the end of p. */ 213 ret = __real_strnlen(p, maxlen < p_size ? maxlen : p_size); 214 if (p_size <= ret && maxlen != ret) 215 fortify_panic(FORTIFY_FUNC_strnlen, FORTIFY_READ); 216 return ret; 217 } 218 219 /* 220 * Defined after fortified strnlen to reuse it. However, it must still be 221 * possible for strlen() to be used on compile-time strings for use in 222 * static initializers (i.e. as a constant expression). 223 */ 224 /** 225 * strlen - Return count of characters in a NUL-terminated string 226 * 227 * @p: pointer to NUL-terminated string to count. 228 * 229 * Do not use this function unless the string length is known at 230 * compile-time. When @p is unterminated, this function may crash 231 * or return unexpected counts that could lead to memory content 232 * exposures. Prefer strnlen(). 233 * 234 * Returns number of characters in @p (NOT including the final NUL). 235 * 236 */ 237 #define strlen(p) \ 238 __builtin_choose_expr(__is_constexpr(__builtin_strlen(p)), \ 239 __builtin_strlen(p), __fortify_strlen(p)) 240 __FORTIFY_INLINE __diagnose_as(__builtin_strlen, 1) 241 __kernel_size_t __fortify_strlen(const char * const POS p) 242 { 243 const size_t p_size = __member_size(p); 244 __kernel_size_t ret; 245 246 /* Give up if we don't know how large p is. */ 247 if (p_size == SIZE_MAX) 248 return __underlying_strlen(p); 249 ret = strnlen(p, p_size); 250 if (p_size <= ret) 251 fortify_panic(FORTIFY_FUNC_strlen, FORTIFY_READ); 252 return ret; 253 } 254 255 /* Defined after fortified strnlen() to reuse it. */ 256 extern ssize_t __real_strscpy(char *, const char *, size_t) __RENAME(sized_strscpy); 257 __FORTIFY_INLINE ssize_t sized_strscpy(char * const POS p, const char * const POS q, size_t size) 258 { 259 /* Use string size rather than possible enclosing struct size. */ 260 const size_t p_size = __member_size(p); 261 const size_t q_size = __member_size(q); 262 size_t len; 263 264 /* If we cannot get size of p and q default to call strscpy. */ 265 if (p_size == SIZE_MAX && q_size == SIZE_MAX) 266 return __real_strscpy(p, q, size); 267 268 /* 269 * If size can be known at compile time and is greater than 270 * p_size, generate a compile time write overflow error. 271 */ 272 if (__compiletime_lessthan(p_size, size)) 273 __write_overflow(); 274 275 /* Short-circuit for compile-time known-safe lengths. */ 276 if (__compiletime_lessthan(p_size, SIZE_MAX)) { 277 len = __compiletime_strlen(q); 278 279 if (len < SIZE_MAX && __compiletime_lessthan(len, size)) { 280 __underlying_memcpy(p, q, len + 1); 281 return len; 282 } 283 } 284 285 /* 286 * This call protects from read overflow, because len will default to q 287 * length if it smaller than size. 288 */ 289 len = strnlen(q, size); 290 /* 291 * If len equals size, we will copy only size bytes which leads to 292 * -E2BIG being returned. 293 * Otherwise we will copy len + 1 because of the final '\O'. 294 */ 295 len = len == size ? size : len + 1; 296 297 /* 298 * Generate a runtime write overflow error if len is greater than 299 * p_size. 300 */ 301 if (len > p_size) 302 fortify_panic(FORTIFY_FUNC_strscpy, FORTIFY_WRITE); 303 304 /* 305 * We can now safely call vanilla strscpy because we are protected from: 306 * 1. Read overflow thanks to call to strnlen(). 307 * 2. Write overflow thanks to above ifs. 308 */ 309 return __real_strscpy(p, q, len); 310 } 311 312 /* Defined after fortified strlen() to reuse it. */ 313 extern size_t __real_strlcat(char *p, const char *q, size_t avail) __RENAME(strlcat); 314 /** 315 * strlcat - Append a string to an existing string 316 * 317 * @p: pointer to %NUL-terminated string to append to 318 * @q: pointer to %NUL-terminated string to append from 319 * @avail: Maximum bytes available in @p 320 * 321 * Appends %NUL-terminated string @q after the %NUL-terminated 322 * string at @p, but will not write beyond @avail bytes total, 323 * potentially truncating the copy from @q. @p will stay 324 * %NUL-terminated only if a %NUL already existed within 325 * the @avail bytes of @p. If so, the resulting number of 326 * bytes copied from @q will be at most "@avail - strlen(@p) - 1". 327 * 328 * Do not use this function. While FORTIFY_SOURCE tries to avoid 329 * read and write overflows, this is only possible when the sizes 330 * of @p and @q are known to the compiler. Prefer building the 331 * string with formatting, via scnprintf(), seq_buf, or similar. 332 * 333 * Returns total bytes that _would_ have been contained by @p 334 * regardless of truncation, similar to snprintf(). If return 335 * value is >= @avail, the string has been truncated. 336 * 337 */ 338 __FORTIFY_INLINE 339 size_t strlcat(char * const POS p, const char * const POS q, size_t avail) 340 { 341 const size_t p_size = __member_size(p); 342 const size_t q_size = __member_size(q); 343 size_t p_len, copy_len; 344 size_t actual, wanted; 345 346 /* Give up immediately if both buffer sizes are unknown. */ 347 if (p_size == SIZE_MAX && q_size == SIZE_MAX) 348 return __real_strlcat(p, q, avail); 349 350 p_len = strnlen(p, avail); 351 copy_len = strlen(q); 352 wanted = actual = p_len + copy_len; 353 354 /* Cannot append any more: report truncation. */ 355 if (avail <= p_len) 356 return wanted; 357 358 /* Give up if string is already overflowed. */ 359 if (p_size <= p_len) 360 fortify_panic(FORTIFY_FUNC_strlcat, FORTIFY_READ); 361 362 if (actual >= avail) { 363 copy_len = avail - p_len - 1; 364 actual = p_len + copy_len; 365 } 366 367 /* Give up if copy will overflow. */ 368 if (p_size <= actual) 369 fortify_panic(FORTIFY_FUNC_strlcat, FORTIFY_WRITE); 370 __underlying_memcpy(p + p_len, q, copy_len); 371 p[actual] = '\0'; 372 373 return wanted; 374 } 375 376 /* Defined after fortified strlcat() to reuse it. */ 377 /** 378 * strcat - Append a string to an existing string 379 * 380 * @p: pointer to NUL-terminated string to append to 381 * @q: pointer to NUL-terminated source string to append from 382 * 383 * Do not use this function. While FORTIFY_SOURCE tries to avoid 384 * read and write overflows, this is only possible when the 385 * destination buffer size is known to the compiler. Prefer 386 * building the string with formatting, via scnprintf() or similar. 387 * At the very least, use strncat(). 388 * 389 * Returns @p. 390 * 391 */ 392 __FORTIFY_INLINE __diagnose_as(__builtin_strcat, 1, 2) 393 char *strcat(char * const POS p, const char *q) 394 { 395 const size_t p_size = __member_size(p); 396 397 if (strlcat(p, q, p_size) >= p_size) 398 fortify_panic(FORTIFY_FUNC_strcat, FORTIFY_WRITE); 399 return p; 400 } 401 402 /** 403 * strncat - Append a string to an existing string 404 * 405 * @p: pointer to NUL-terminated string to append to 406 * @q: pointer to source string to append from 407 * @count: Maximum bytes to read from @q 408 * 409 * Appends at most @count bytes from @q (stopping at the first 410 * NUL byte) after the NUL-terminated string at @p. @p will be 411 * NUL-terminated. 412 * 413 * Do not use this function. While FORTIFY_SOURCE tries to avoid 414 * read and write overflows, this is only possible when the sizes 415 * of @p and @q are known to the compiler. Prefer building the 416 * string with formatting, via scnprintf() or similar. 417 * 418 * Returns @p. 419 * 420 */ 421 /* Defined after fortified strlen() and strnlen() to reuse them. */ 422 __FORTIFY_INLINE __diagnose_as(__builtin_strncat, 1, 2, 3) 423 char *strncat(char * const POS p, const char * const POS q, __kernel_size_t count) 424 { 425 const size_t p_size = __member_size(p); 426 const size_t q_size = __member_size(q); 427 size_t p_len, copy_len; 428 429 if (p_size == SIZE_MAX && q_size == SIZE_MAX) 430 return __underlying_strncat(p, q, count); 431 p_len = strlen(p); 432 copy_len = strnlen(q, count); 433 if (p_size < p_len + copy_len + 1) 434 fortify_panic(FORTIFY_FUNC_strncat, FORTIFY_WRITE); 435 __underlying_memcpy(p + p_len, q, copy_len); 436 p[p_len + copy_len] = '\0'; 437 return p; 438 } 439 440 __FORTIFY_INLINE void fortify_memset_chk(__kernel_size_t size, 441 const size_t p_size, 442 const size_t p_size_field) 443 { 444 if (__builtin_constant_p(size)) { 445 /* 446 * Length argument is a constant expression, so we 447 * can perform compile-time bounds checking where 448 * buffer sizes are also known at compile time. 449 */ 450 451 /* Error when size is larger than enclosing struct. */ 452 if (__compiletime_lessthan(p_size_field, p_size) && 453 __compiletime_lessthan(p_size, size)) 454 __write_overflow(); 455 456 /* Warn when write size is larger than dest field. */ 457 if (__compiletime_lessthan(p_size_field, size)) 458 __write_overflow_field(p_size_field, size); 459 } 460 /* 461 * At this point, length argument may not be a constant expression, 462 * so run-time bounds checking can be done where buffer sizes are 463 * known. (This is not an "else" because the above checks may only 464 * be compile-time warnings, and we want to still warn for run-time 465 * overflows.) 466 */ 467 468 /* 469 * Always stop accesses beyond the struct that contains the 470 * field, when the buffer's remaining size is known. 471 * (The SIZE_MAX test is to optimize away checks where the buffer 472 * lengths are unknown.) 473 */ 474 if (p_size != SIZE_MAX && p_size < size) 475 fortify_panic(FORTIFY_FUNC_memset, FORTIFY_WRITE); 476 } 477 478 #define __fortify_memset_chk(p, c, size, p_size, p_size_field) ({ \ 479 size_t __fortify_size = (size_t)(size); \ 480 fortify_memset_chk(__fortify_size, p_size, p_size_field), \ 481 __underlying_memset(p, c, __fortify_size); \ 482 }) 483 484 /* 485 * __struct_size() vs __member_size() must be captured here to avoid 486 * evaluating argument side-effects further into the macro layers. 487 */ 488 #ifndef CONFIG_KMSAN 489 #define memset(p, c, s) __fortify_memset_chk(p, c, s, \ 490 __struct_size(p), __member_size(p)) 491 #endif 492 493 /* 494 * To make sure the compiler can enforce protection against buffer overflows, 495 * memcpy(), memmove(), and memset() must not be used beyond individual 496 * struct members. If you need to copy across multiple members, please use 497 * struct_group() to create a named mirror of an anonymous struct union. 498 * (e.g. see struct sk_buff.) Read overflow checking is currently only 499 * done when a write overflow is also present, or when building with W=1. 500 * 501 * Mitigation coverage matrix 502 * Bounds checking at: 503 * +-------+-------+-------+-------+ 504 * | Compile time | Run time | 505 * memcpy() argument sizes: | write | read | write | read | 506 * dest source length +-------+-------+-------+-------+ 507 * memcpy(known, known, constant) | y | y | n/a | n/a | 508 * memcpy(known, unknown, constant) | y | n | n/a | V | 509 * memcpy(known, known, dynamic) | n | n | B | B | 510 * memcpy(known, unknown, dynamic) | n | n | B | V | 511 * memcpy(unknown, known, constant) | n | y | V | n/a | 512 * memcpy(unknown, unknown, constant) | n | n | V | V | 513 * memcpy(unknown, known, dynamic) | n | n | V | B | 514 * memcpy(unknown, unknown, dynamic) | n | n | V | V | 515 * +-------+-------+-------+-------+ 516 * 517 * y = perform deterministic compile-time bounds checking 518 * n = cannot perform deterministic compile-time bounds checking 519 * n/a = no run-time bounds checking needed since compile-time deterministic 520 * B = can perform run-time bounds checking (currently unimplemented) 521 * V = vulnerable to run-time overflow (will need refactoring to solve) 522 * 523 */ 524 __FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size, 525 const size_t p_size, 526 const size_t q_size, 527 const size_t p_size_field, 528 const size_t q_size_field, 529 const u8 func) 530 { 531 if (__builtin_constant_p(size)) { 532 /* 533 * Length argument is a constant expression, so we 534 * can perform compile-time bounds checking where 535 * buffer sizes are also known at compile time. 536 */ 537 538 /* Error when size is larger than enclosing struct. */ 539 if (__compiletime_lessthan(p_size_field, p_size) && 540 __compiletime_lessthan(p_size, size)) 541 __write_overflow(); 542 if (__compiletime_lessthan(q_size_field, q_size) && 543 __compiletime_lessthan(q_size, size)) 544 __read_overflow2(); 545 546 /* Warn when write size argument larger than dest field. */ 547 if (__compiletime_lessthan(p_size_field, size)) 548 __write_overflow_field(p_size_field, size); 549 /* 550 * Warn for source field over-read when building with W=1 551 * or when an over-write happened, so both can be fixed at 552 * the same time. 553 */ 554 if ((IS_ENABLED(KBUILD_EXTRA_WARN1) || 555 __compiletime_lessthan(p_size_field, size)) && 556 __compiletime_lessthan(q_size_field, size)) 557 __read_overflow2_field(q_size_field, size); 558 } 559 /* 560 * At this point, length argument may not be a constant expression, 561 * so run-time bounds checking can be done where buffer sizes are 562 * known. (This is not an "else" because the above checks may only 563 * be compile-time warnings, and we want to still warn for run-time 564 * overflows.) 565 */ 566 567 /* 568 * Always stop accesses beyond the struct that contains the 569 * field, when the buffer's remaining size is known. 570 * (The SIZE_MAX test is to optimize away checks where the buffer 571 * lengths are unknown.) 572 */ 573 if (p_size != SIZE_MAX && p_size < size) 574 fortify_panic(func, FORTIFY_WRITE); 575 else if (q_size != SIZE_MAX && q_size < size) 576 fortify_panic(func, FORTIFY_READ); 577 578 /* 579 * Warn when writing beyond destination field size. 580 * 581 * We must ignore p_size_field == 0 for existing 0-element 582 * fake flexible arrays, until they are all converted to 583 * proper flexible arrays. 584 * 585 * The implementation of __builtin_*object_size() behaves 586 * like sizeof() when not directly referencing a flexible 587 * array member, which means there will be many bounds checks 588 * that will appear at run-time, without a way for them to be 589 * detected at compile-time (as can be done when the destination 590 * is specifically the flexible array member). 591 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101832 592 */ 593 if (p_size_field != 0 && p_size_field != SIZE_MAX && 594 p_size != p_size_field && p_size_field < size) 595 return true; 596 597 return false; 598 } 599 600 #define __fortify_memcpy_chk(p, q, size, p_size, q_size, \ 601 p_size_field, q_size_field, op) ({ \ 602 const size_t __fortify_size = (size_t)(size); \ 603 const size_t __p_size = (p_size); \ 604 const size_t __q_size = (q_size); \ 605 const size_t __p_size_field = (p_size_field); \ 606 const size_t __q_size_field = (q_size_field); \ 607 WARN_ONCE(fortify_memcpy_chk(__fortify_size, __p_size, \ 608 __q_size, __p_size_field, \ 609 __q_size_field, FORTIFY_FUNC_ ##op), \ 610 #op ": detected field-spanning write (size %zu) of single %s (size %zu)\n", \ 611 __fortify_size, \ 612 "field \"" #p "\" at " FILE_LINE, \ 613 __p_size_field); \ 614 __underlying_##op(p, q, __fortify_size); \ 615 }) 616 617 /* 618 * Notes about compile-time buffer size detection: 619 * 620 * With these types... 621 * 622 * struct middle { 623 * u16 a; 624 * u8 middle_buf[16]; 625 * int b; 626 * }; 627 * struct end { 628 * u16 a; 629 * u8 end_buf[16]; 630 * }; 631 * struct flex { 632 * int a; 633 * u8 flex_buf[]; 634 * }; 635 * 636 * void func(TYPE *ptr) { ... } 637 * 638 * Cases where destination size cannot be currently detected: 639 * - the size of ptr's object (seemingly by design, gcc & clang fail): 640 * __builtin_object_size(ptr, 1) == SIZE_MAX 641 * - the size of flexible arrays in ptr's obj (by design, dynamic size): 642 * __builtin_object_size(ptr->flex_buf, 1) == SIZE_MAX 643 * - the size of ANY array at the end of ptr's obj (gcc and clang bug): 644 * __builtin_object_size(ptr->end_buf, 1) == SIZE_MAX 645 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836 646 * 647 * Cases where destination size is currently detected: 648 * - the size of non-array members within ptr's object: 649 * __builtin_object_size(ptr->a, 1) == 2 650 * - the size of non-flexible-array in the middle of ptr's obj: 651 * __builtin_object_size(ptr->middle_buf, 1) == 16 652 * 653 */ 654 655 /* 656 * __struct_size() vs __member_size() must be captured here to avoid 657 * evaluating argument side-effects further into the macro layers. 658 */ 659 #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ 660 __struct_size(p), __struct_size(q), \ 661 __member_size(p), __member_size(q), \ 662 memcpy) 663 #define memmove(p, q, s) __fortify_memcpy_chk(p, q, s, \ 664 __struct_size(p), __struct_size(q), \ 665 __member_size(p), __member_size(q), \ 666 memmove) 667 668 extern void *__real_memscan(void *, int, __kernel_size_t) __RENAME(memscan); 669 __FORTIFY_INLINE void *memscan(void * const POS0 p, int c, __kernel_size_t size) 670 { 671 const size_t p_size = __struct_size(p); 672 673 if (__compiletime_lessthan(p_size, size)) 674 __read_overflow(); 675 if (p_size < size) 676 fortify_panic(FORTIFY_FUNC_memscan, FORTIFY_READ); 677 return __real_memscan(p, c, size); 678 } 679 680 __FORTIFY_INLINE __diagnose_as(__builtin_memcmp, 1, 2, 3) 681 int memcmp(const void * const POS0 p, const void * const POS0 q, __kernel_size_t size) 682 { 683 const size_t p_size = __struct_size(p); 684 const size_t q_size = __struct_size(q); 685 686 if (__builtin_constant_p(size)) { 687 if (__compiletime_lessthan(p_size, size)) 688 __read_overflow(); 689 if (__compiletime_lessthan(q_size, size)) 690 __read_overflow2(); 691 } 692 if (p_size < size || q_size < size) 693 fortify_panic(FORTIFY_FUNC_memcmp, FORTIFY_READ); 694 return __underlying_memcmp(p, q, size); 695 } 696 697 __FORTIFY_INLINE __diagnose_as(__builtin_memchr, 1, 2, 3) 698 void *memchr(const void * const POS0 p, int c, __kernel_size_t size) 699 { 700 const size_t p_size = __struct_size(p); 701 702 if (__compiletime_lessthan(p_size, size)) 703 __read_overflow(); 704 if (p_size < size) 705 fortify_panic(FORTIFY_FUNC_memchr, FORTIFY_READ); 706 return __underlying_memchr(p, c, size); 707 } 708 709 void *__real_memchr_inv(const void *s, int c, size_t n) __RENAME(memchr_inv); 710 __FORTIFY_INLINE void *memchr_inv(const void * const POS0 p, int c, size_t size) 711 { 712 const size_t p_size = __struct_size(p); 713 714 if (__compiletime_lessthan(p_size, size)) 715 __read_overflow(); 716 if (p_size < size) 717 fortify_panic(FORTIFY_FUNC_memchr_inv, FORTIFY_READ); 718 return __real_memchr_inv(p, c, size); 719 } 720 721 extern void *__real_kmemdup(const void *src, size_t len, gfp_t gfp) __RENAME(kmemdup) 722 __realloc_size(2); 723 __FORTIFY_INLINE void *kmemdup(const void * const POS0 p, size_t size, gfp_t gfp) 724 { 725 const size_t p_size = __struct_size(p); 726 727 if (__compiletime_lessthan(p_size, size)) 728 __read_overflow(); 729 if (p_size < size) 730 fortify_panic(FORTIFY_FUNC_kmemdup, FORTIFY_READ); 731 return __real_kmemdup(p, size, gfp); 732 } 733 734 /** 735 * strcpy - Copy a string into another string buffer 736 * 737 * @p: pointer to destination of copy 738 * @q: pointer to NUL-terminated source string to copy 739 * 740 * Do not use this function. While FORTIFY_SOURCE tries to avoid 741 * overflows, this is only possible when the sizes of @q and @p are 742 * known to the compiler. Prefer strscpy(), though note its different 743 * return values for detecting truncation. 744 * 745 * Returns @p. 746 * 747 */ 748 /* Defined after fortified strlen to reuse it. */ 749 __FORTIFY_INLINE __diagnose_as(__builtin_strcpy, 1, 2) 750 char *strcpy(char * const POS p, const char * const POS q) 751 { 752 const size_t p_size = __member_size(p); 753 const size_t q_size = __member_size(q); 754 size_t size; 755 756 /* If neither buffer size is known, immediately give up. */ 757 if (__builtin_constant_p(p_size) && 758 __builtin_constant_p(q_size) && 759 p_size == SIZE_MAX && q_size == SIZE_MAX) 760 return __underlying_strcpy(p, q); 761 size = strlen(q) + 1; 762 /* Compile-time check for const size overflow. */ 763 if (__compiletime_lessthan(p_size, size)) 764 __write_overflow(); 765 /* Run-time check for dynamic size overflow. */ 766 if (p_size < size) 767 fortify_panic(FORTIFY_FUNC_strcpy, FORTIFY_WRITE); 768 __underlying_memcpy(p, q, size); 769 return p; 770 } 771 772 /* Don't use these outside the FORITFY_SOURCE implementation */ 773 #undef __underlying_memchr 774 #undef __underlying_memcmp 775 #undef __underlying_strcat 776 #undef __underlying_strcpy 777 #undef __underlying_strlen 778 #undef __underlying_strncat 779 #undef __underlying_strncpy 780 781 #undef POS 782 #undef POS0 783 784 #endif /* _LINUX_FORTIFY_STRING_H_ */ 785