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 #ifndef fortify_panic 19 # define fortify_panic(func, write, retfail) \ 20 __fortify_panic(FORTIFY_REASON(func, write)) 21 #endif 22 23 #define FORTIFY_READ 0 24 #define FORTIFY_WRITE 1 25 26 #define EACH_FORTIFY_FUNC(macro) \ 27 macro(strncpy), \ 28 macro(strnlen), \ 29 macro(strlen), \ 30 macro(strscpy), \ 31 macro(strlcat), \ 32 macro(strcat), \ 33 macro(strncat), \ 34 macro(memset), \ 35 macro(memcpy), \ 36 macro(memmove), \ 37 macro(memscan), \ 38 macro(memcmp), \ 39 macro(memchr), \ 40 macro(memchr_inv), \ 41 macro(kmemdup), \ 42 macro(strcpy), \ 43 macro(UNKNOWN), 44 45 #define MAKE_FORTIFY_FUNC(func) FORTIFY_FUNC_##func 46 47 enum fortify_func { 48 EACH_FORTIFY_FUNC(MAKE_FORTIFY_FUNC) 49 }; 50 51 void __fortify_report(const u8 reason); 52 void __fortify_panic(const u8 reason) __cold __noreturn; 53 void __read_overflow(void) __compiletime_error("detected read beyond size of object (1st parameter)"); 54 void __read_overflow2(void) __compiletime_error("detected read beyond size of object (2nd parameter)"); 55 void __read_overflow2_field(size_t avail, size_t wanted) __compiletime_warning("detected read beyond size of field (2nd parameter); maybe use struct_group()?"); 56 void __write_overflow(void) __compiletime_error("detected write beyond size of object (1st parameter)"); 57 void __write_overflow_field(size_t avail, size_t wanted) __compiletime_warning("detected write beyond size of field (1st parameter); maybe use struct_group()?"); 58 59 #define __compiletime_strlen(p) \ 60 ({ \ 61 char *__p = (char *)(p); \ 62 size_t __ret = SIZE_MAX; \ 63 const size_t __p_size = __member_size(p); \ 64 if (__p_size != SIZE_MAX && \ 65 __builtin_constant_p(*__p)) { \ 66 size_t __p_len = __p_size - 1; \ 67 if (__builtin_constant_p(__p[__p_len]) && \ 68 __p[__p_len] == '\0') \ 69 __ret = __builtin_strlen(__p); \ 70 } \ 71 __ret; \ 72 }) 73 74 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS) 75 extern void *__underlying_memchr(const void *p, int c, __kernel_size_t size) __RENAME(memchr); 76 extern int __underlying_memcmp(const void *p, const void *q, __kernel_size_t size) __RENAME(memcmp); 77 extern void *__underlying_memcpy(void *p, const void *q, __kernel_size_t size) __RENAME(memcpy); 78 extern void *__underlying_memmove(void *p, const void *q, __kernel_size_t size) __RENAME(memmove); 79 extern void *__underlying_memset(void *p, int c, __kernel_size_t size) __RENAME(memset); 80 extern char *__underlying_strcat(char *p, const char *q) __RENAME(strcat); 81 extern char *__underlying_strcpy(char *p, const char *q) __RENAME(strcpy); 82 extern __kernel_size_t __underlying_strlen(const char *p) __RENAME(strlen); 83 extern char *__underlying_strncat(char *p, const char *q, __kernel_size_t count) __RENAME(strncat); 84 extern char *__underlying_strncpy(char *p, const char *q, __kernel_size_t size) __RENAME(strncpy); 85 #else 86 87 #if defined(__SANITIZE_MEMORY__) 88 /* 89 * For KMSAN builds all memcpy/memset/memmove calls should be replaced by the 90 * corresponding __msan_XXX functions. 91 */ 92 #include <linux/kmsan_string.h> 93 #define __underlying_memcpy __msan_memcpy 94 #define __underlying_memmove __msan_memmove 95 #define __underlying_memset __msan_memset 96 #else 97 #define __underlying_memcpy __builtin_memcpy 98 #define __underlying_memmove __builtin_memmove 99 #define __underlying_memset __builtin_memset 100 #endif 101 102 #define __underlying_memchr __builtin_memchr 103 #define __underlying_memcmp __builtin_memcmp 104 #define __underlying_strcat __builtin_strcat 105 #define __underlying_strcpy __builtin_strcpy 106 #define __underlying_strlen __builtin_strlen 107 #define __underlying_strncat __builtin_strncat 108 #define __underlying_strncpy __builtin_strncpy 109 #endif 110 111 /** 112 * unsafe_memcpy - memcpy implementation with no FORTIFY bounds checking 113 * 114 * @dst: Destination memory address to write to 115 * @src: Source memory address to read from 116 * @bytes: How many bytes to write to @dst from @src 117 * @justification: Free-form text or comment describing why the use is needed 118 * 119 * This should be used for corner cases where the compiler cannot do the 120 * right thing, or during transitions between APIs, etc. It should be used 121 * very rarely, and includes a place for justification detailing where bounds 122 * checking has happened, and why existing solutions cannot be employed. 123 */ 124 #define unsafe_memcpy(dst, src, bytes, justification) \ 125 __underlying_memcpy(dst, src, bytes) 126 127 /* 128 * Clang's use of __builtin_*object_size() within inlines needs hinting via 129 * __pass_*object_size(). The preference is to only ever use type 1 (member 130 * size, rather than struct size), but there remain some stragglers using 131 * type 0 that will be converted in the future. 132 */ 133 #if __has_builtin(__builtin_dynamic_object_size) 134 #define POS __pass_dynamic_object_size(1) 135 #define POS0 __pass_dynamic_object_size(0) 136 #else 137 #define POS __pass_object_size(1) 138 #define POS0 __pass_object_size(0) 139 #endif 140 141 #define __compiletime_lessthan(bounds, length) ( \ 142 __builtin_constant_p((bounds) < (length)) && \ 143 (bounds) < (length) \ 144 ) 145 146 /** 147 * strncpy - Copy a string to memory with non-guaranteed NUL padding 148 * 149 * @p: pointer to destination of copy 150 * @q: pointer to NUL-terminated source string to copy 151 * @size: bytes to write at @p 152 * 153 * If strlen(@q) >= @size, the copy of @q will stop after @size bytes, 154 * and @p will NOT be NUL-terminated 155 * 156 * If strlen(@q) < @size, following the copy of @q, trailing NUL bytes 157 * will be written to @p until @size total bytes have been written. 158 * 159 * Do not use this function. While FORTIFY_SOURCE tries to avoid 160 * over-reads of @q, it cannot defend against writing unterminated 161 * results to @p. Using strncpy() remains ambiguous and fragile. 162 * Instead, please choose an alternative, so that the expectation 163 * of @p's contents is unambiguous: 164 * 165 * +--------------------+--------------------+------------+ 166 * | **p** needs to be: | padded to **size** | not padded | 167 * +====================+====================+============+ 168 * | NUL-terminated | strscpy_pad() | strscpy() | 169 * +--------------------+--------------------+------------+ 170 * | not NUL-terminated | strtomem_pad() | strtomem() | 171 * +--------------------+--------------------+------------+ 172 * 173 * Note strscpy*()'s differing return values for detecting truncation, 174 * and strtomem*()'s expectation that the destination is marked with 175 * __nonstring when it is a character array. 176 * 177 */ 178 __FORTIFY_INLINE __diagnose_as(__builtin_strncpy, 1, 2, 3) 179 char *strncpy(char * const POS p, const char *q, __kernel_size_t size) 180 { 181 const size_t p_size = __member_size(p); 182 183 if (__compiletime_lessthan(p_size, size)) 184 __write_overflow(); 185 if (p_size < size) 186 fortify_panic(FORTIFY_FUNC_strncpy, FORTIFY_WRITE, p); 187 return __underlying_strncpy(p, q, size); 188 } 189 190 extern __kernel_size_t __real_strnlen(const char *, __kernel_size_t) __RENAME(strnlen); 191 /** 192 * strnlen - Return bounded count of characters in a NUL-terminated string 193 * 194 * @p: pointer to NUL-terminated string to count. 195 * @maxlen: maximum number of characters to count. 196 * 197 * Returns number of characters in @p (NOT including the final NUL), or 198 * @maxlen, if no NUL has been found up to there. 199 * 200 */ 201 __FORTIFY_INLINE __kernel_size_t strnlen(const char * const POS p, __kernel_size_t maxlen) 202 { 203 const size_t p_size = __member_size(p); 204 const size_t p_len = __compiletime_strlen(p); 205 size_t ret; 206 207 /* We can take compile-time actions when maxlen is const. */ 208 if (__builtin_constant_p(maxlen) && p_len != SIZE_MAX) { 209 /* If p is const, we can use its compile-time-known len. */ 210 if (maxlen >= p_size) 211 return p_len; 212 } 213 214 /* Do not check characters beyond the end of p. */ 215 ret = __real_strnlen(p, maxlen < p_size ? maxlen : p_size); 216 if (p_size <= ret && maxlen != ret) 217 fortify_panic(FORTIFY_FUNC_strnlen, FORTIFY_READ, ret); 218 return ret; 219 } 220 221 /* 222 * Defined after fortified strnlen to reuse it. However, it must still be 223 * possible for strlen() to be used on compile-time strings for use in 224 * static initializers (i.e. as a constant expression). 225 */ 226 /** 227 * strlen - Return count of characters in a NUL-terminated string 228 * 229 * @p: pointer to NUL-terminated string to count. 230 * 231 * Do not use this function unless the string length is known at 232 * compile-time. When @p is unterminated, this function may crash 233 * or return unexpected counts that could lead to memory content 234 * exposures. Prefer strnlen(). 235 * 236 * Returns number of characters in @p (NOT including the final NUL). 237 * 238 */ 239 #define strlen(p) \ 240 __builtin_choose_expr(__is_constexpr(__builtin_strlen(p)), \ 241 __builtin_strlen(p), __fortify_strlen(p)) 242 __FORTIFY_INLINE __diagnose_as(__builtin_strlen, 1) 243 __kernel_size_t __fortify_strlen(const char * const POS p) 244 { 245 const size_t p_size = __member_size(p); 246 __kernel_size_t ret; 247 248 /* Give up if we don't know how large p is. */ 249 if (p_size == SIZE_MAX) 250 return __underlying_strlen(p); 251 ret = strnlen(p, p_size); 252 if (p_size <= ret) 253 fortify_panic(FORTIFY_FUNC_strlen, FORTIFY_READ, ret); 254 return ret; 255 } 256 257 /* Defined after fortified strnlen() to reuse it. */ 258 extern ssize_t __real_strscpy(char *, const char *, size_t) __RENAME(sized_strscpy); 259 __FORTIFY_INLINE ssize_t sized_strscpy(char * const POS p, const char * const POS q, size_t size) 260 { 261 /* Use string size rather than possible enclosing struct size. */ 262 const size_t p_size = __member_size(p); 263 const size_t q_size = __member_size(q); 264 size_t len; 265 266 /* If we cannot get size of p and q default to call strscpy. */ 267 if (p_size == SIZE_MAX && q_size == SIZE_MAX) 268 return __real_strscpy(p, q, size); 269 270 /* 271 * If size can be known at compile time and is greater than 272 * p_size, generate a compile time write overflow error. 273 */ 274 if (__compiletime_lessthan(p_size, size)) 275 __write_overflow(); 276 277 /* Short-circuit for compile-time known-safe lengths. */ 278 if (__compiletime_lessthan(p_size, SIZE_MAX)) { 279 len = __compiletime_strlen(q); 280 281 if (len < SIZE_MAX && __compiletime_lessthan(len, size)) { 282 __underlying_memcpy(p, q, len + 1); 283 return len; 284 } 285 } 286 287 /* 288 * This call protects from read overflow, because len will default to q 289 * length if it smaller than size. 290 */ 291 len = strnlen(q, size); 292 /* 293 * If len equals size, we will copy only size bytes which leads to 294 * -E2BIG being returned. 295 * Otherwise we will copy len + 1 because of the final '\O'. 296 */ 297 len = len == size ? size : len + 1; 298 299 /* 300 * Generate a runtime write overflow error if len is greater than 301 * p_size. 302 */ 303 if (len > p_size) 304 fortify_panic(FORTIFY_FUNC_strscpy, FORTIFY_WRITE, -E2BIG); 305 306 /* 307 * We can now safely call vanilla strscpy because we are protected from: 308 * 1. Read overflow thanks to call to strnlen(). 309 * 2. Write overflow thanks to above ifs. 310 */ 311 return __real_strscpy(p, q, len); 312 } 313 314 /* Defined after fortified strlen() to reuse it. */ 315 extern size_t __real_strlcat(char *p, const char *q, size_t avail) __RENAME(strlcat); 316 /** 317 * strlcat - Append a string to an existing string 318 * 319 * @p: pointer to %NUL-terminated string to append to 320 * @q: pointer to %NUL-terminated string to append from 321 * @avail: Maximum bytes available in @p 322 * 323 * Appends %NUL-terminated string @q after the %NUL-terminated 324 * string at @p, but will not write beyond @avail bytes total, 325 * potentially truncating the copy from @q. @p will stay 326 * %NUL-terminated only if a %NUL already existed within 327 * the @avail bytes of @p. If so, the resulting number of 328 * bytes copied from @q will be at most "@avail - strlen(@p) - 1". 329 * 330 * Do not use this function. While FORTIFY_SOURCE tries to avoid 331 * read and write overflows, this is only possible when the sizes 332 * of @p and @q are known to the compiler. Prefer building the 333 * string with formatting, via scnprintf(), seq_buf, or similar. 334 * 335 * Returns total bytes that _would_ have been contained by @p 336 * regardless of truncation, similar to snprintf(). If return 337 * value is >= @avail, the string has been truncated. 338 * 339 */ 340 __FORTIFY_INLINE 341 size_t strlcat(char * const POS p, const char * const POS q, size_t avail) 342 { 343 const size_t p_size = __member_size(p); 344 const size_t q_size = __member_size(q); 345 size_t p_len, copy_len; 346 size_t actual, wanted; 347 348 /* Give up immediately if both buffer sizes are unknown. */ 349 if (p_size == SIZE_MAX && q_size == SIZE_MAX) 350 return __real_strlcat(p, q, avail); 351 352 p_len = strnlen(p, avail); 353 copy_len = strlen(q); 354 wanted = actual = p_len + copy_len; 355 356 /* Cannot append any more: report truncation. */ 357 if (avail <= p_len) 358 return wanted; 359 360 /* Give up if string is already overflowed. */ 361 if (p_size <= p_len) 362 fortify_panic(FORTIFY_FUNC_strlcat, FORTIFY_READ, wanted); 363 364 if (actual >= avail) { 365 copy_len = avail - p_len - 1; 366 actual = p_len + copy_len; 367 } 368 369 /* Give up if copy will overflow. */ 370 if (p_size <= actual) 371 fortify_panic(FORTIFY_FUNC_strlcat, FORTIFY_WRITE, wanted); 372 __underlying_memcpy(p + p_len, q, copy_len); 373 p[actual] = '\0'; 374 375 return wanted; 376 } 377 378 /* Defined after fortified strlcat() to reuse it. */ 379 /** 380 * strcat - Append a string to an existing string 381 * 382 * @p: pointer to NUL-terminated string to append to 383 * @q: pointer to NUL-terminated source string to append from 384 * 385 * Do not use this function. While FORTIFY_SOURCE tries to avoid 386 * read and write overflows, this is only possible when the 387 * destination buffer size is known to the compiler. Prefer 388 * building the string with formatting, via scnprintf() or similar. 389 * At the very least, use strncat(). 390 * 391 * Returns @p. 392 * 393 */ 394 __FORTIFY_INLINE __diagnose_as(__builtin_strcat, 1, 2) 395 char *strcat(char * const POS p, const char *q) 396 { 397 const size_t p_size = __member_size(p); 398 399 if (strlcat(p, q, p_size) >= p_size) 400 fortify_panic(FORTIFY_FUNC_strcat, FORTIFY_WRITE, p); 401 return p; 402 } 403 404 /** 405 * strncat - Append a string to an existing string 406 * 407 * @p: pointer to NUL-terminated string to append to 408 * @q: pointer to source string to append from 409 * @count: Maximum bytes to read from @q 410 * 411 * Appends at most @count bytes from @q (stopping at the first 412 * NUL byte) after the NUL-terminated string at @p. @p will be 413 * NUL-terminated. 414 * 415 * Do not use this function. While FORTIFY_SOURCE tries to avoid 416 * read and write overflows, this is only possible when the sizes 417 * of @p and @q are known to the compiler. Prefer building the 418 * string with formatting, via scnprintf() or similar. 419 * 420 * Returns @p. 421 * 422 */ 423 /* Defined after fortified strlen() and strnlen() to reuse them. */ 424 __FORTIFY_INLINE __diagnose_as(__builtin_strncat, 1, 2, 3) 425 char *strncat(char * const POS p, const char * const POS q, __kernel_size_t count) 426 { 427 const size_t p_size = __member_size(p); 428 const size_t q_size = __member_size(q); 429 size_t p_len, copy_len; 430 431 if (p_size == SIZE_MAX && q_size == SIZE_MAX) 432 return __underlying_strncat(p, q, count); 433 p_len = strlen(p); 434 copy_len = strnlen(q, count); 435 if (p_size < p_len + copy_len + 1) 436 fortify_panic(FORTIFY_FUNC_strncat, FORTIFY_WRITE, p); 437 __underlying_memcpy(p + p_len, q, copy_len); 438 p[p_len + copy_len] = '\0'; 439 return p; 440 } 441 442 __FORTIFY_INLINE bool fortify_memset_chk(__kernel_size_t size, 443 const size_t p_size, 444 const size_t p_size_field) 445 { 446 if (__builtin_constant_p(size)) { 447 /* 448 * Length argument is a constant expression, so we 449 * can perform compile-time bounds checking where 450 * buffer sizes are also known at compile time. 451 */ 452 453 /* Error when size is larger than enclosing struct. */ 454 if (__compiletime_lessthan(p_size_field, p_size) && 455 __compiletime_lessthan(p_size, size)) 456 __write_overflow(); 457 458 /* Warn when write size is larger than dest field. */ 459 if (__compiletime_lessthan(p_size_field, size)) 460 __write_overflow_field(p_size_field, size); 461 } 462 /* 463 * At this point, length argument may not be a constant expression, 464 * so run-time bounds checking can be done where buffer sizes are 465 * known. (This is not an "else" because the above checks may only 466 * be compile-time warnings, and we want to still warn for run-time 467 * overflows.) 468 */ 469 470 /* 471 * Always stop accesses beyond the struct that contains the 472 * field, when the buffer's remaining size is known. 473 * (The SIZE_MAX test is to optimize away checks where the buffer 474 * lengths are unknown.) 475 */ 476 if (p_size != SIZE_MAX && p_size < size) 477 fortify_panic(FORTIFY_FUNC_memset, FORTIFY_WRITE, true); 478 return false; 479 } 480 481 #define __fortify_memset_chk(p, c, size, p_size, p_size_field) ({ \ 482 size_t __fortify_size = (size_t)(size); \ 483 fortify_memset_chk(__fortify_size, p_size, p_size_field), \ 484 __underlying_memset(p, c, __fortify_size); \ 485 }) 486 487 /* 488 * __struct_size() vs __member_size() must be captured here to avoid 489 * evaluating argument side-effects further into the macro layers. 490 */ 491 #ifndef CONFIG_KMSAN 492 #define memset(p, c, s) __fortify_memset_chk(p, c, s, \ 493 __struct_size(p), __member_size(p)) 494 #endif 495 496 /* 497 * To make sure the compiler can enforce protection against buffer overflows, 498 * memcpy(), memmove(), and memset() must not be used beyond individual 499 * struct members. If you need to copy across multiple members, please use 500 * struct_group() to create a named mirror of an anonymous struct union. 501 * (e.g. see struct sk_buff.) Read overflow checking is currently only 502 * done when a write overflow is also present, or when building with W=1. 503 * 504 * Mitigation coverage matrix 505 * Bounds checking at: 506 * +-------+-------+-------+-------+ 507 * | Compile time | Run time | 508 * memcpy() argument sizes: | write | read | write | read | 509 * dest source length +-------+-------+-------+-------+ 510 * memcpy(known, known, constant) | y | y | n/a | n/a | 511 * memcpy(known, unknown, constant) | y | n | n/a | V | 512 * memcpy(known, known, dynamic) | n | n | B | B | 513 * memcpy(known, unknown, dynamic) | n | n | B | V | 514 * memcpy(unknown, known, constant) | n | y | V | n/a | 515 * memcpy(unknown, unknown, constant) | n | n | V | V | 516 * memcpy(unknown, known, dynamic) | n | n | V | B | 517 * memcpy(unknown, unknown, dynamic) | n | n | V | V | 518 * +-------+-------+-------+-------+ 519 * 520 * y = perform deterministic compile-time bounds checking 521 * n = cannot perform deterministic compile-time bounds checking 522 * n/a = no run-time bounds checking needed since compile-time deterministic 523 * B = can perform run-time bounds checking (currently unimplemented) 524 * V = vulnerable to run-time overflow (will need refactoring to solve) 525 * 526 */ 527 __FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size, 528 const size_t p_size, 529 const size_t q_size, 530 const size_t p_size_field, 531 const size_t q_size_field, 532 const u8 func) 533 { 534 if (__builtin_constant_p(size)) { 535 /* 536 * Length argument is a constant expression, so we 537 * can perform compile-time bounds checking where 538 * buffer sizes are also known at compile time. 539 */ 540 541 /* Error when size is larger than enclosing struct. */ 542 if (__compiletime_lessthan(p_size_field, p_size) && 543 __compiletime_lessthan(p_size, size)) 544 __write_overflow(); 545 if (__compiletime_lessthan(q_size_field, q_size) && 546 __compiletime_lessthan(q_size, size)) 547 __read_overflow2(); 548 549 /* Warn when write size argument larger than dest field. */ 550 if (__compiletime_lessthan(p_size_field, size)) 551 __write_overflow_field(p_size_field, size); 552 /* 553 * Warn for source field over-read when building with W=1 554 * or when an over-write happened, so both can be fixed at 555 * the same time. 556 */ 557 if ((IS_ENABLED(KBUILD_EXTRA_WARN1) || 558 __compiletime_lessthan(p_size_field, size)) && 559 __compiletime_lessthan(q_size_field, size)) 560 __read_overflow2_field(q_size_field, size); 561 } 562 /* 563 * At this point, length argument may not be a constant expression, 564 * so run-time bounds checking can be done where buffer sizes are 565 * known. (This is not an "else" because the above checks may only 566 * be compile-time warnings, and we want to still warn for run-time 567 * overflows.) 568 */ 569 570 /* 571 * Always stop accesses beyond the struct that contains the 572 * field, when the buffer's remaining size is known. 573 * (The SIZE_MAX test is to optimize away checks where the buffer 574 * lengths are unknown.) 575 */ 576 if (p_size != SIZE_MAX && p_size < size) 577 fortify_panic(func, FORTIFY_WRITE, true); 578 else if (q_size != SIZE_MAX && q_size < size) 579 fortify_panic(func, FORTIFY_READ, true); 580 581 /* 582 * Warn when writing beyond destination field size. 583 * 584 * We must ignore p_size_field == 0 for existing 0-element 585 * fake flexible arrays, until they are all converted to 586 * proper flexible arrays. 587 * 588 * The implementation of __builtin_*object_size() behaves 589 * like sizeof() when not directly referencing a flexible 590 * array member, which means there will be many bounds checks 591 * that will appear at run-time, without a way for them to be 592 * detected at compile-time (as can be done when the destination 593 * is specifically the flexible array member). 594 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101832 595 */ 596 if (p_size_field != 0 && p_size_field != SIZE_MAX && 597 p_size != p_size_field && p_size_field < size) 598 return true; 599 600 return false; 601 } 602 603 #define __fortify_memcpy_chk(p, q, size, p_size, q_size, \ 604 p_size_field, q_size_field, op) ({ \ 605 const size_t __fortify_size = (size_t)(size); \ 606 const size_t __p_size = (p_size); \ 607 const size_t __q_size = (q_size); \ 608 const size_t __p_size_field = (p_size_field); \ 609 const size_t __q_size_field = (q_size_field); \ 610 WARN_ONCE(fortify_memcpy_chk(__fortify_size, __p_size, \ 611 __q_size, __p_size_field, \ 612 __q_size_field, FORTIFY_FUNC_ ##op), \ 613 #op ": detected field-spanning write (size %zu) of single %s (size %zu)\n", \ 614 __fortify_size, \ 615 "field \"" #p "\" at " FILE_LINE, \ 616 __p_size_field); \ 617 __underlying_##op(p, q, __fortify_size); \ 618 }) 619 620 /* 621 * Notes about compile-time buffer size detection: 622 * 623 * With these types... 624 * 625 * struct middle { 626 * u16 a; 627 * u8 middle_buf[16]; 628 * int b; 629 * }; 630 * struct end { 631 * u16 a; 632 * u8 end_buf[16]; 633 * }; 634 * struct flex { 635 * int a; 636 * u8 flex_buf[]; 637 * }; 638 * 639 * void func(TYPE *ptr) { ... } 640 * 641 * Cases where destination size cannot be currently detected: 642 * - the size of ptr's object (seemingly by design, gcc & clang fail): 643 * __builtin_object_size(ptr, 1) == SIZE_MAX 644 * - the size of flexible arrays in ptr's obj (by design, dynamic size): 645 * __builtin_object_size(ptr->flex_buf, 1) == SIZE_MAX 646 * - the size of ANY array at the end of ptr's obj (gcc and clang bug): 647 * __builtin_object_size(ptr->end_buf, 1) == SIZE_MAX 648 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836 649 * 650 * Cases where destination size is currently detected: 651 * - the size of non-array members within ptr's object: 652 * __builtin_object_size(ptr->a, 1) == 2 653 * - the size of non-flexible-array in the middle of ptr's obj: 654 * __builtin_object_size(ptr->middle_buf, 1) == 16 655 * 656 */ 657 658 /* 659 * __struct_size() vs __member_size() must be captured here to avoid 660 * evaluating argument side-effects further into the macro layers. 661 */ 662 #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ 663 __struct_size(p), __struct_size(q), \ 664 __member_size(p), __member_size(q), \ 665 memcpy) 666 #define memmove(p, q, s) __fortify_memcpy_chk(p, q, s, \ 667 __struct_size(p), __struct_size(q), \ 668 __member_size(p), __member_size(q), \ 669 memmove) 670 671 extern void *__real_memscan(void *, int, __kernel_size_t) __RENAME(memscan); 672 __FORTIFY_INLINE void *memscan(void * const POS0 p, int c, __kernel_size_t size) 673 { 674 const size_t p_size = __struct_size(p); 675 676 if (__compiletime_lessthan(p_size, size)) 677 __read_overflow(); 678 if (p_size < size) 679 fortify_panic(FORTIFY_FUNC_memscan, FORTIFY_READ, NULL); 680 return __real_memscan(p, c, size); 681 } 682 683 __FORTIFY_INLINE __diagnose_as(__builtin_memcmp, 1, 2, 3) 684 int memcmp(const void * const POS0 p, const void * const POS0 q, __kernel_size_t size) 685 { 686 const size_t p_size = __struct_size(p); 687 const size_t q_size = __struct_size(q); 688 689 if (__builtin_constant_p(size)) { 690 if (__compiletime_lessthan(p_size, size)) 691 __read_overflow(); 692 if (__compiletime_lessthan(q_size, size)) 693 __read_overflow2(); 694 } 695 if (p_size < size || q_size < size) 696 fortify_panic(FORTIFY_FUNC_memcmp, FORTIFY_READ, INT_MIN); 697 return __underlying_memcmp(p, q, size); 698 } 699 700 __FORTIFY_INLINE __diagnose_as(__builtin_memchr, 1, 2, 3) 701 void *memchr(const void * const POS0 p, int c, __kernel_size_t size) 702 { 703 const size_t p_size = __struct_size(p); 704 705 if (__compiletime_lessthan(p_size, size)) 706 __read_overflow(); 707 if (p_size < size) 708 fortify_panic(FORTIFY_FUNC_memchr, FORTIFY_READ, NULL); 709 return __underlying_memchr(p, c, size); 710 } 711 712 void *__real_memchr_inv(const void *s, int c, size_t n) __RENAME(memchr_inv); 713 __FORTIFY_INLINE void *memchr_inv(const void * const POS0 p, int c, size_t size) 714 { 715 const size_t p_size = __struct_size(p); 716 717 if (__compiletime_lessthan(p_size, size)) 718 __read_overflow(); 719 if (p_size < size) 720 fortify_panic(FORTIFY_FUNC_memchr_inv, FORTIFY_READ, NULL); 721 return __real_memchr_inv(p, c, size); 722 } 723 724 extern void *__real_kmemdup(const void *src, size_t len, gfp_t gfp) __RENAME(kmemdup) 725 __realloc_size(2); 726 __FORTIFY_INLINE void *kmemdup(const void * const POS0 p, size_t size, gfp_t gfp) 727 { 728 const size_t p_size = __struct_size(p); 729 730 if (__compiletime_lessthan(p_size, size)) 731 __read_overflow(); 732 if (p_size < size) 733 fortify_panic(FORTIFY_FUNC_kmemdup, FORTIFY_READ, NULL); 734 return __real_kmemdup(p, size, gfp); 735 } 736 737 /** 738 * strcpy - Copy a string into another string buffer 739 * 740 * @p: pointer to destination of copy 741 * @q: pointer to NUL-terminated source string to copy 742 * 743 * Do not use this function. While FORTIFY_SOURCE tries to avoid 744 * overflows, this is only possible when the sizes of @q and @p are 745 * known to the compiler. Prefer strscpy(), though note its different 746 * return values for detecting truncation. 747 * 748 * Returns @p. 749 * 750 */ 751 /* Defined after fortified strlen to reuse it. */ 752 __FORTIFY_INLINE __diagnose_as(__builtin_strcpy, 1, 2) 753 char *strcpy(char * const POS p, const char * const POS q) 754 { 755 const size_t p_size = __member_size(p); 756 const size_t q_size = __member_size(q); 757 size_t size; 758 759 /* If neither buffer size is known, immediately give up. */ 760 if (__builtin_constant_p(p_size) && 761 __builtin_constant_p(q_size) && 762 p_size == SIZE_MAX && q_size == SIZE_MAX) 763 return __underlying_strcpy(p, q); 764 size = strlen(q) + 1; 765 /* Compile-time check for const size overflow. */ 766 if (__compiletime_lessthan(p_size, size)) 767 __write_overflow(); 768 /* Run-time check for dynamic size overflow. */ 769 if (p_size < size) 770 fortify_panic(FORTIFY_FUNC_strcpy, FORTIFY_WRITE, p); 771 __underlying_memcpy(p, q, size); 772 return p; 773 } 774 775 /* Don't use these outside the FORITFY_SOURCE implementation */ 776 #undef __underlying_memchr 777 #undef __underlying_memcmp 778 #undef __underlying_strcat 779 #undef __underlying_strcpy 780 #undef __underlying_strlen 781 #undef __underlying_strncat 782 #undef __underlying_strncpy 783 784 #undef POS 785 #undef POS0 786 787 #endif /* _LINUX_FORTIFY_STRING_H_ */ 788