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, avail, size, retfail) \ 20 __fortify_panic(FORTIFY_REASON(func, write), avail, size) 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 47enum fortify_func { 48 EACH_FORTIFY_FUNC(MAKE_FORTIFY_FUNC) 49}; 50 51void __fortify_report(const u8 reason, const size_t avail, const size_t size); 52void __fortify_panic(const u8 reason, const size_t avail, const size_t size) __cold __noreturn; 53void __read_overflow(void) __compiletime_error("detected read beyond size of object (1st parameter)"); 54void __read_overflow2(void) __compiletime_error("detected read beyond size of object (2nd parameter)"); 55void __read_overflow2_field(size_t avail, size_t wanted) __compiletime_warning("detected read beyond size of field (2nd parameter); maybe use struct_group()?"); 56void __write_overflow(void) __compiletime_error("detected write beyond size of object (1st parameter)"); 57void __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) 75extern void *__underlying_memchr(const void *p, int c, __kernel_size_t size) __RENAME(memchr); 76extern int __underlying_memcmp(const void *p, const void *q, __kernel_size_t size) __RENAME(memcmp); 77extern void *__underlying_memcpy(void *p, const void *q, __kernel_size_t size) __RENAME(memcpy); 78extern void *__underlying_memmove(void *p, const void *q, __kernel_size_t size) __RENAME(memmove); 79extern void *__underlying_memset(void *p, int c, __kernel_size_t size) __RENAME(memset); 80extern char *__underlying_strcat(char *p, const char *q) __RENAME(strcat); 81extern char *__underlying_strcpy(char *p, const char *q) __RENAME(strcpy); 82extern __kernel_size_t __underlying_strlen(const char *p) __RENAME(strlen); 83extern char *__underlying_strncat(char *p, const char *q, __kernel_size_t count) __RENAME(strncat); 84extern 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) 179char *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_size, size, p); 187 return __underlying_strncpy(p, q, size); 188} 189 190extern __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, p_size, ret + 1, 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, p_size, ret + 1, ret); 254 return ret; 255} 256 257/* Defined after fortified strnlen() to reuse it. */ 258extern 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 (p_size < len) 304 fortify_panic(FORTIFY_FUNC_strscpy, FORTIFY_WRITE, p_size, len, -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. */ 315extern 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 341size_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, p_size, p_len + 1, 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, p_size, actual + 1, 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) 395char *strcat(char * const POS p, const char *q) 396{ 397 const size_t p_size = __member_size(p); 398 const size_t wanted = strlcat(p, q, p_size); 399 400 if (p_size <= wanted) 401 fortify_panic(FORTIFY_FUNC_strcat, FORTIFY_WRITE, p_size, wanted + 1, p); 402 return p; 403} 404 405/** 406 * strncat - Append a string to an existing string 407 * 408 * @p: pointer to NUL-terminated string to append to 409 * @q: pointer to source string to append from 410 * @count: Maximum bytes to read from @q 411 * 412 * Appends at most @count bytes from @q (stopping at the first 413 * NUL byte) after the NUL-terminated string at @p. @p will be 414 * NUL-terminated. 415 * 416 * Do not use this function. While FORTIFY_SOURCE tries to avoid 417 * read and write overflows, this is only possible when the sizes 418 * of @p and @q are known to the compiler. Prefer building the 419 * string with formatting, via scnprintf() or similar. 420 * 421 * Returns @p. 422 * 423 */ 424/* Defined after fortified strlen() and strnlen() to reuse them. */ 425__FORTIFY_INLINE __diagnose_as(__builtin_strncat, 1, 2, 3) 426char *strncat(char * const POS p, const char * const POS q, __kernel_size_t count) 427{ 428 const size_t p_size = __member_size(p); 429 const size_t q_size = __member_size(q); 430 size_t p_len, copy_len, total; 431 432 if (p_size == SIZE_MAX && q_size == SIZE_MAX) 433 return __underlying_strncat(p, q, count); 434 p_len = strlen(p); 435 copy_len = strnlen(q, count); 436 total = p_len + copy_len + 1; 437 if (p_size < total) 438 fortify_panic(FORTIFY_FUNC_strncat, FORTIFY_WRITE, p_size, total, p); 439 __underlying_memcpy(p + p_len, q, copy_len); 440 p[p_len + copy_len] = '\0'; 441 return p; 442} 443 444__FORTIFY_INLINE bool fortify_memset_chk(__kernel_size_t size, 445 const size_t p_size, 446 const size_t p_size_field) 447{ 448 if (__builtin_constant_p(size)) { 449 /* 450 * Length argument is a constant expression, so we 451 * can perform compile-time bounds checking where 452 * buffer sizes are also known at compile time. 453 */ 454 455 /* Error when size is larger than enclosing struct. */ 456 if (__compiletime_lessthan(p_size_field, p_size) && 457 __compiletime_lessthan(p_size, size)) 458 __write_overflow(); 459 460 /* Warn when write size is larger than dest field. */ 461 if (__compiletime_lessthan(p_size_field, size)) 462 __write_overflow_field(p_size_field, size); 463 } 464 /* 465 * At this point, length argument may not be a constant expression, 466 * so run-time bounds checking can be done where buffer sizes are 467 * known. (This is not an "else" because the above checks may only 468 * be compile-time warnings, and we want to still warn for run-time 469 * overflows.) 470 */ 471 472 /* 473 * Always stop accesses beyond the struct that contains the 474 * field, when the buffer's remaining size is known. 475 * (The SIZE_MAX test is to optimize away checks where the buffer 476 * lengths are unknown.) 477 */ 478 if (p_size != SIZE_MAX && p_size < size) 479 fortify_panic(FORTIFY_FUNC_memset, FORTIFY_WRITE, p_size, size, true); 480 return false; 481} 482 483#define __fortify_memset_chk(p, c, size, p_size, p_size_field) ({ \ 484 size_t __fortify_size = (size_t)(size); \ 485 fortify_memset_chk(__fortify_size, p_size, p_size_field), \ 486 __underlying_memset(p, c, __fortify_size); \ 487}) 488 489/* 490 * __struct_size() vs __member_size() must be captured here to avoid 491 * evaluating argument side-effects further into the macro layers. 492 */ 493#ifndef CONFIG_KMSAN 494#define memset(p, c, s) __fortify_memset_chk(p, c, s, \ 495 __struct_size(p), __member_size(p)) 496#endif 497 498/* 499 * To make sure the compiler can enforce protection against buffer overflows, 500 * memcpy(), memmove(), and memset() must not be used beyond individual 501 * struct members. If you need to copy across multiple members, please use 502 * struct_group() to create a named mirror of an anonymous struct union. 503 * (e.g. see struct sk_buff.) Read overflow checking is currently only 504 * done when a write overflow is also present, or when building with W=1. 505 * 506 * Mitigation coverage matrix 507 * Bounds checking at: 508 * +-------+-------+-------+-------+ 509 * | Compile time | Run time | 510 * memcpy() argument sizes: | write | read | write | read | 511 * dest source length +-------+-------+-------+-------+ 512 * memcpy(known, known, constant) | y | y | n/a | n/a | 513 * memcpy(known, unknown, constant) | y | n | n/a | V | 514 * memcpy(known, known, dynamic) | n | n | B | B | 515 * memcpy(known, unknown, dynamic) | n | n | B | V | 516 * memcpy(unknown, known, constant) | n | y | V | n/a | 517 * memcpy(unknown, unknown, constant) | n | n | V | V | 518 * memcpy(unknown, known, dynamic) | n | n | V | B | 519 * memcpy(unknown, unknown, dynamic) | n | n | V | V | 520 * +-------+-------+-------+-------+ 521 * 522 * y = perform deterministic compile-time bounds checking 523 * n = cannot perform deterministic compile-time bounds checking 524 * n/a = no run-time bounds checking needed since compile-time deterministic 525 * B = can perform run-time bounds checking (currently unimplemented) 526 * V = vulnerable to run-time overflow (will need refactoring to solve) 527 * 528 */ 529__FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size, 530 const size_t p_size, 531 const size_t q_size, 532 const size_t p_size_field, 533 const size_t q_size_field, 534 const u8 func) 535{ 536 if (__builtin_constant_p(size)) { 537 /* 538 * Length argument is a constant expression, so we 539 * can perform compile-time bounds checking where 540 * buffer sizes are also known at compile time. 541 */ 542 543 /* Error when size is larger than enclosing struct. */ 544 if (__compiletime_lessthan(p_size_field, p_size) && 545 __compiletime_lessthan(p_size, size)) 546 __write_overflow(); 547 if (__compiletime_lessthan(q_size_field, q_size) && 548 __compiletime_lessthan(q_size, size)) 549 __read_overflow2(); 550 551 /* Warn when write size argument larger than dest field. */ 552 if (__compiletime_lessthan(p_size_field, size)) 553 __write_overflow_field(p_size_field, size); 554 /* 555 * Warn for source field over-read when building with W=1 556 * or when an over-write happened, so both can be fixed at 557 * the same time. 558 */ 559 if ((IS_ENABLED(KBUILD_EXTRA_WARN1) || 560 __compiletime_lessthan(p_size_field, size)) && 561 __compiletime_lessthan(q_size_field, size)) 562 __read_overflow2_field(q_size_field, size); 563 } 564 /* 565 * At this point, length argument may not be a constant expression, 566 * so run-time bounds checking can be done where buffer sizes are 567 * known. (This is not an "else" because the above checks may only 568 * be compile-time warnings, and we want to still warn for run-time 569 * overflows.) 570 */ 571 572 /* 573 * Always stop accesses beyond the struct that contains the 574 * field, when the buffer's remaining size is known. 575 * (The SIZE_MAX test is to optimize away checks where the buffer 576 * lengths are unknown.) 577 */ 578 if (p_size != SIZE_MAX && p_size < size) 579 fortify_panic(func, FORTIFY_WRITE, p_size, size, true); 580 else if (q_size != SIZE_MAX && q_size < size) 581 fortify_panic(func, FORTIFY_READ, p_size, size, true); 582 583 /* 584 * Warn when writing beyond destination field size. 585 * 586 * We must ignore p_size_field == 0 for existing 0-element 587 * fake flexible arrays, until they are all converted to 588 * proper flexible arrays. 589 * 590 * The implementation of __builtin_*object_size() behaves 591 * like sizeof() when not directly referencing a flexible 592 * array member, which means there will be many bounds checks 593 * that will appear at run-time, without a way for them to be 594 * detected at compile-time (as can be done when the destination 595 * is specifically the flexible array member). 596 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101832 597 */ 598 if (p_size_field != 0 && p_size_field != SIZE_MAX && 599 p_size != p_size_field && p_size_field < size) 600 return true; 601 602 return false; 603} 604 605#define __fortify_memcpy_chk(p, q, size, p_size, q_size, \ 606 p_size_field, q_size_field, op) ({ \ 607 const size_t __fortify_size = (size_t)(size); \ 608 const size_t __p_size = (p_size); \ 609 const size_t __q_size = (q_size); \ 610 const size_t __p_size_field = (p_size_field); \ 611 const size_t __q_size_field = (q_size_field); \ 612 WARN_ONCE(fortify_memcpy_chk(__fortify_size, __p_size, \ 613 __q_size, __p_size_field, \ 614 __q_size_field, FORTIFY_FUNC_ ##op), \ 615 #op ": detected field-spanning write (size %zu) of single %s (size %zu)\n", \ 616 __fortify_size, \ 617 "field \"" #p "\" at " FILE_LINE, \ 618 __p_size_field); \ 619 __underlying_##op(p, q, __fortify_size); \ 620}) 621 622/* 623 * Notes about compile-time buffer size detection: 624 * 625 * With these types... 626 * 627 * struct middle { 628 * u16 a; 629 * u8 middle_buf[16]; 630 * int b; 631 * }; 632 * struct end { 633 * u16 a; 634 * u8 end_buf[16]; 635 * }; 636 * struct flex { 637 * int a; 638 * u8 flex_buf[]; 639 * }; 640 * 641 * void func(TYPE *ptr) { ... } 642 * 643 * Cases where destination size cannot be currently detected: 644 * - the size of ptr's object (seemingly by design, gcc & clang fail): 645 * __builtin_object_size(ptr, 1) == SIZE_MAX 646 * - the size of flexible arrays in ptr's obj (by design, dynamic size): 647 * __builtin_object_size(ptr->flex_buf, 1) == SIZE_MAX 648 * - the size of ANY array at the end of ptr's obj (gcc and clang bug): 649 * __builtin_object_size(ptr->end_buf, 1) == SIZE_MAX 650 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836 651 * 652 * Cases where destination size is currently detected: 653 * - the size of non-array members within ptr's object: 654 * __builtin_object_size(ptr->a, 1) == 2 655 * - the size of non-flexible-array in the middle of ptr's obj: 656 * __builtin_object_size(ptr->middle_buf, 1) == 16 657 * 658 */ 659 660/* 661 * __struct_size() vs __member_size() must be captured here to avoid 662 * evaluating argument side-effects further into the macro layers. 663 */ 664#define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ 665 __struct_size(p), __struct_size(q), \ 666 __member_size(p), __member_size(q), \ 667 memcpy) 668#define memmove(p, q, s) __fortify_memcpy_chk(p, q, s, \ 669 __struct_size(p), __struct_size(q), \ 670 __member_size(p), __member_size(q), \ 671 memmove) 672 673extern void *__real_memscan(void *, int, __kernel_size_t) __RENAME(memscan); 674__FORTIFY_INLINE void *memscan(void * const POS0 p, int c, __kernel_size_t size) 675{ 676 const size_t p_size = __struct_size(p); 677 678 if (__compiletime_lessthan(p_size, size)) 679 __read_overflow(); 680 if (p_size < size) 681 fortify_panic(FORTIFY_FUNC_memscan, FORTIFY_READ, p_size, size, NULL); 682 return __real_memscan(p, c, size); 683} 684 685__FORTIFY_INLINE __diagnose_as(__builtin_memcmp, 1, 2, 3) 686int memcmp(const void * const POS0 p, const void * const POS0 q, __kernel_size_t size) 687{ 688 const size_t p_size = __struct_size(p); 689 const size_t q_size = __struct_size(q); 690 691 if (__builtin_constant_p(size)) { 692 if (__compiletime_lessthan(p_size, size)) 693 __read_overflow(); 694 if (__compiletime_lessthan(q_size, size)) 695 __read_overflow2(); 696 } 697 if (p_size < size) 698 fortify_panic(FORTIFY_FUNC_memcmp, FORTIFY_READ, p_size, size, INT_MIN); 699 else if (q_size < size) 700 fortify_panic(FORTIFY_FUNC_memcmp, FORTIFY_READ, q_size, size, INT_MIN); 701 return __underlying_memcmp(p, q, size); 702} 703 704__FORTIFY_INLINE __diagnose_as(__builtin_memchr, 1, 2, 3) 705void *memchr(const void * const POS0 p, int c, __kernel_size_t size) 706{ 707 const size_t p_size = __struct_size(p); 708 709 if (__compiletime_lessthan(p_size, size)) 710 __read_overflow(); 711 if (p_size < size) 712 fortify_panic(FORTIFY_FUNC_memchr, FORTIFY_READ, p_size, size, NULL); 713 return __underlying_memchr(p, c, size); 714} 715 716void *__real_memchr_inv(const void *s, int c, size_t n) __RENAME(memchr_inv); 717__FORTIFY_INLINE void *memchr_inv(const void * const POS0 p, int c, size_t size) 718{ 719 const size_t p_size = __struct_size(p); 720 721 if (__compiletime_lessthan(p_size, size)) 722 __read_overflow(); 723 if (p_size < size) 724 fortify_panic(FORTIFY_FUNC_memchr_inv, FORTIFY_READ, p_size, size, NULL); 725 return __real_memchr_inv(p, c, size); 726} 727 728extern void *__real_kmemdup(const void *src, size_t len, gfp_t gfp) __RENAME(kmemdup) 729 __realloc_size(2); 730__FORTIFY_INLINE void *kmemdup(const void * const POS0 p, size_t size, gfp_t gfp) 731{ 732 const size_t p_size = __struct_size(p); 733 734 if (__compiletime_lessthan(p_size, size)) 735 __read_overflow(); 736 if (p_size < size) 737 fortify_panic(FORTIFY_FUNC_kmemdup, FORTIFY_READ, p_size, size, NULL); 738 return __real_kmemdup(p, size, gfp); 739} 740 741/** 742 * strcpy - Copy a string into another string buffer 743 * 744 * @p: pointer to destination of copy 745 * @q: pointer to NUL-terminated source string to copy 746 * 747 * Do not use this function. While FORTIFY_SOURCE tries to avoid 748 * overflows, this is only possible when the sizes of @q and @p are 749 * known to the compiler. Prefer strscpy(), though note its different 750 * return values for detecting truncation. 751 * 752 * Returns @p. 753 * 754 */ 755/* Defined after fortified strlen to reuse it. */ 756__FORTIFY_INLINE __diagnose_as(__builtin_strcpy, 1, 2) 757char *strcpy(char * const POS p, const char * const POS q) 758{ 759 const size_t p_size = __member_size(p); 760 const size_t q_size = __member_size(q); 761 size_t size; 762 763 /* If neither buffer size is known, immediately give up. */ 764 if (__builtin_constant_p(p_size) && 765 __builtin_constant_p(q_size) && 766 p_size == SIZE_MAX && q_size == SIZE_MAX) 767 return __underlying_strcpy(p, q); 768 size = strlen(q) + 1; 769 /* Compile-time check for const size overflow. */ 770 if (__compiletime_lessthan(p_size, size)) 771 __write_overflow(); 772 /* Run-time check for dynamic size overflow. */ 773 if (p_size < size) 774 fortify_panic(FORTIFY_FUNC_strcpy, FORTIFY_WRITE, p_size, size, p); 775 __underlying_memcpy(p, q, size); 776 return p; 777} 778 779/* Don't use these outside the FORITFY_SOURCE implementation */ 780#undef __underlying_memchr 781#undef __underlying_memcmp 782#undef __underlying_strcat 783#undef __underlying_strcpy 784#undef __underlying_strlen 785#undef __underlying_strncat 786#undef __underlying_strncpy 787 788#undef POS 789#undef POS0 790 791#endif /* _LINUX_FORTIFY_STRING_H_ */ 792