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