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Message-ID: <202501181300.b3wcBpIt-lkp@intel.com>
Date: Sat, 18 Jan 2025 13:44:50 +0800
From: kernel test robot <lkp@...el.com>
To: Kees Cook <keescook@...omium.org>
Cc: oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: include/linux/fortify-string.h:387:25: warning: call to
'__read_overflow2_field' declared with attribute warning: detected read
beyond size of field (2nd parameter); maybe use struct_group()?
tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head: 595523945be0a5a2f12a1c04772383293fbc04a1
commit: ba38961a069b0d8d03b53218a6c29d737577d448 um: Enable FORTIFY_SOURCE
date: 2 years, 4 months ago
config: um-randconfig-r052-20240430 (https://download.01.org/0day-ci/archive/20250118/202501181300.b3wcBpIt-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250118/202501181300.b3wcBpIt-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202501181300.b3wcBpIt-lkp@intel.com/
All warnings (new ones prefixed by >>):
In file included from include/linux/string.h:253,
from include/linux/bitmap.h:11,
from include/linux/cpumask.h:12,
from include/linux/mm_types_task.h:14,
from include/linux/mm_types.h:5,
from include/linux/buildid.h:5,
from include/linux/module.h:14,
from drivers/net/ethernet/intel/igb/igb_main.c:6:
In function 'fortify_memcpy_chk',
inlined from 'igb_get_stats64' at drivers/net/ethernet/intel/igb/igb_main.c:6539:2:
>> include/linux/fortify-string.h:387:25: warning: call to '__read_overflow2_field' declared with attribute warning: detected read beyond size of field (2nd parameter); maybe use struct_group()? [-Wattribute-warning]
387 | __read_overflow2_field(q_size_field, size);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
vim +/__read_overflow2_field +387 include/linux/fortify-string.h
28e77cc1c06866 Kees Cook 2021-06-16 318
28e77cc1c06866 Kees Cook 2021-06-16 319 /*
28e77cc1c06866 Kees Cook 2021-06-16 320 * __builtin_object_size() must be captured here to avoid evaluating argument
28e77cc1c06866 Kees Cook 2021-06-16 321 * side-effects further into the macro layers.
28e77cc1c06866 Kees Cook 2021-06-16 322 */
28e77cc1c06866 Kees Cook 2021-06-16 323 #define memset(p, c, s) __fortify_memset_chk(p, c, s, \
28e77cc1c06866 Kees Cook 2021-06-16 324 __builtin_object_size(p, 0), __builtin_object_size(p, 1))
a28a6e860c6cf2 Francis Laniel 2021-02-25 325
f68f2ff91512c1 Kees Cook 2021-04-20 326 /*
f68f2ff91512c1 Kees Cook 2021-04-20 327 * To make sure the compiler can enforce protection against buffer overflows,
f68f2ff91512c1 Kees Cook 2021-04-20 328 * memcpy(), memmove(), and memset() must not be used beyond individual
f68f2ff91512c1 Kees Cook 2021-04-20 329 * struct members. If you need to copy across multiple members, please use
f68f2ff91512c1 Kees Cook 2021-04-20 330 * struct_group() to create a named mirror of an anonymous struct union.
f68f2ff91512c1 Kees Cook 2021-04-20 331 * (e.g. see struct sk_buff.) Read overflow checking is currently only
f68f2ff91512c1 Kees Cook 2021-04-20 332 * done when a write overflow is also present, or when building with W=1.
f68f2ff91512c1 Kees Cook 2021-04-20 333 *
f68f2ff91512c1 Kees Cook 2021-04-20 334 * Mitigation coverage matrix
f68f2ff91512c1 Kees Cook 2021-04-20 335 * Bounds checking at:
f68f2ff91512c1 Kees Cook 2021-04-20 336 * +-------+-------+-------+-------+
f68f2ff91512c1 Kees Cook 2021-04-20 337 * | Compile time | Run time |
f68f2ff91512c1 Kees Cook 2021-04-20 338 * memcpy() argument sizes: | write | read | write | read |
f68f2ff91512c1 Kees Cook 2021-04-20 339 * dest source length +-------+-------+-------+-------+
f68f2ff91512c1 Kees Cook 2021-04-20 340 * memcpy(known, known, constant) | y | y | n/a | n/a |
f68f2ff91512c1 Kees Cook 2021-04-20 341 * memcpy(known, unknown, constant) | y | n | n/a | V |
f68f2ff91512c1 Kees Cook 2021-04-20 342 * memcpy(known, known, dynamic) | n | n | B | B |
f68f2ff91512c1 Kees Cook 2021-04-20 343 * memcpy(known, unknown, dynamic) | n | n | B | V |
f68f2ff91512c1 Kees Cook 2021-04-20 344 * memcpy(unknown, known, constant) | n | y | V | n/a |
f68f2ff91512c1 Kees Cook 2021-04-20 345 * memcpy(unknown, unknown, constant) | n | n | V | V |
f68f2ff91512c1 Kees Cook 2021-04-20 346 * memcpy(unknown, known, dynamic) | n | n | V | B |
f68f2ff91512c1 Kees Cook 2021-04-20 347 * memcpy(unknown, unknown, dynamic) | n | n | V | V |
f68f2ff91512c1 Kees Cook 2021-04-20 348 * +-------+-------+-------+-------+
f68f2ff91512c1 Kees Cook 2021-04-20 349 *
f68f2ff91512c1 Kees Cook 2021-04-20 350 * y = perform deterministic compile-time bounds checking
f68f2ff91512c1 Kees Cook 2021-04-20 351 * n = cannot perform deterministic compile-time bounds checking
f68f2ff91512c1 Kees Cook 2021-04-20 352 * n/a = no run-time bounds checking needed since compile-time deterministic
f68f2ff91512c1 Kees Cook 2021-04-20 353 * B = can perform run-time bounds checking (currently unimplemented)
f68f2ff91512c1 Kees Cook 2021-04-20 354 * V = vulnerable to run-time overflow (will need refactoring to solve)
f68f2ff91512c1 Kees Cook 2021-04-20 355 *
f68f2ff91512c1 Kees Cook 2021-04-20 356 */
54d9469bc515dc Kees Cook 2021-06-24 357 __FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size,
f68f2ff91512c1 Kees Cook 2021-04-20 358 const size_t p_size,
f68f2ff91512c1 Kees Cook 2021-04-20 359 const size_t q_size,
f68f2ff91512c1 Kees Cook 2021-04-20 360 const size_t p_size_field,
f68f2ff91512c1 Kees Cook 2021-04-20 361 const size_t q_size_field,
f68f2ff91512c1 Kees Cook 2021-04-20 362 const char *func)
a28a6e860c6cf2 Francis Laniel 2021-02-25 363 {
a28a6e860c6cf2 Francis Laniel 2021-02-25 364 if (__builtin_constant_p(size)) {
f68f2ff91512c1 Kees Cook 2021-04-20 365 /*
f68f2ff91512c1 Kees Cook 2021-04-20 366 * Length argument is a constant expression, so we
f68f2ff91512c1 Kees Cook 2021-04-20 367 * can perform compile-time bounds checking where
f68f2ff91512c1 Kees Cook 2021-04-20 368 * buffer sizes are known.
f68f2ff91512c1 Kees Cook 2021-04-20 369 */
f68f2ff91512c1 Kees Cook 2021-04-20 370
f68f2ff91512c1 Kees Cook 2021-04-20 371 /* Error when size is larger than enclosing struct. */
f68f2ff91512c1 Kees Cook 2021-04-20 372 if (p_size > p_size_field && p_size < size)
a28a6e860c6cf2 Francis Laniel 2021-02-25 373 __write_overflow();
f68f2ff91512c1 Kees Cook 2021-04-20 374 if (q_size > q_size_field && q_size < size)
a28a6e860c6cf2 Francis Laniel 2021-02-25 375 __read_overflow2();
f68f2ff91512c1 Kees Cook 2021-04-20 376
f68f2ff91512c1 Kees Cook 2021-04-20 377 /* Warn when write size argument larger than dest field. */
f68f2ff91512c1 Kees Cook 2021-04-20 378 if (p_size_field < size)
f68f2ff91512c1 Kees Cook 2021-04-20 379 __write_overflow_field(p_size_field, size);
f68f2ff91512c1 Kees Cook 2021-04-20 380 /*
f68f2ff91512c1 Kees Cook 2021-04-20 381 * Warn for source field over-read when building with W=1
f68f2ff91512c1 Kees Cook 2021-04-20 382 * or when an over-write happened, so both can be fixed at
f68f2ff91512c1 Kees Cook 2021-04-20 383 * the same time.
f68f2ff91512c1 Kees Cook 2021-04-20 384 */
f68f2ff91512c1 Kees Cook 2021-04-20 385 if ((IS_ENABLED(KBUILD_EXTRA_WARN1) || p_size_field < size) &&
f68f2ff91512c1 Kees Cook 2021-04-20 386 q_size_field < size)
f68f2ff91512c1 Kees Cook 2021-04-20 @387 __read_overflow2_field(q_size_field, size);
a28a6e860c6cf2 Francis Laniel 2021-02-25 388 }
f68f2ff91512c1 Kees Cook 2021-04-20 389 /*
f68f2ff91512c1 Kees Cook 2021-04-20 390 * At this point, length argument may not be a constant expression,
f68f2ff91512c1 Kees Cook 2021-04-20 391 * so run-time bounds checking can be done where buffer sizes are
f68f2ff91512c1 Kees Cook 2021-04-20 392 * known. (This is not an "else" because the above checks may only
f68f2ff91512c1 Kees Cook 2021-04-20 393 * be compile-time warnings, and we want to still warn for run-time
f68f2ff91512c1 Kees Cook 2021-04-20 394 * overflows.)
f68f2ff91512c1 Kees Cook 2021-04-20 395 */
f68f2ff91512c1 Kees Cook 2021-04-20 396
f68f2ff91512c1 Kees Cook 2021-04-20 397 /*
f68f2ff91512c1 Kees Cook 2021-04-20 398 * Always stop accesses beyond the struct that contains the
f68f2ff91512c1 Kees Cook 2021-04-20 399 * field, when the buffer's remaining size is known.
311fb40aa0569a Kees Cook 2022-09-02 400 * (The SIZE_MAX test is to optimize away checks where the buffer
f68f2ff91512c1 Kees Cook 2021-04-20 401 * lengths are unknown.)
f68f2ff91512c1 Kees Cook 2021-04-20 402 */
311fb40aa0569a Kees Cook 2022-09-02 403 if ((p_size != SIZE_MAX && p_size < size) ||
311fb40aa0569a Kees Cook 2022-09-02 404 (q_size != SIZE_MAX && q_size < size))
f68f2ff91512c1 Kees Cook 2021-04-20 405 fortify_panic(func);
54d9469bc515dc Kees Cook 2021-06-24 406
54d9469bc515dc Kees Cook 2021-06-24 407 /*
54d9469bc515dc Kees Cook 2021-06-24 408 * Warn when writing beyond destination field size.
54d9469bc515dc Kees Cook 2021-06-24 409 *
54d9469bc515dc Kees Cook 2021-06-24 410 * We must ignore p_size_field == 0 for existing 0-element
54d9469bc515dc Kees Cook 2021-06-24 411 * fake flexible arrays, until they are all converted to
54d9469bc515dc Kees Cook 2021-06-24 412 * proper flexible arrays.
54d9469bc515dc Kees Cook 2021-06-24 413 *
54d9469bc515dc Kees Cook 2021-06-24 414 * The implementation of __builtin_object_size() behaves
54d9469bc515dc Kees Cook 2021-06-24 415 * like sizeof() when not directly referencing a flexible
54d9469bc515dc Kees Cook 2021-06-24 416 * array member, which means there will be many bounds checks
54d9469bc515dc Kees Cook 2021-06-24 417 * that will appear at run-time, without a way for them to be
54d9469bc515dc Kees Cook 2021-06-24 418 * detected at compile-time (as can be done when the destination
54d9469bc515dc Kees Cook 2021-06-24 419 * is specifically the flexible array member).
54d9469bc515dc Kees Cook 2021-06-24 420 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101832
54d9469bc515dc Kees Cook 2021-06-24 421 */
54d9469bc515dc Kees Cook 2021-06-24 422 if (p_size_field != 0 && p_size_field != SIZE_MAX &&
54d9469bc515dc Kees Cook 2021-06-24 423 p_size != p_size_field && p_size_field < size)
54d9469bc515dc Kees Cook 2021-06-24 424 return true;
54d9469bc515dc Kees Cook 2021-06-24 425
54d9469bc515dc Kees Cook 2021-06-24 426 return false;
a28a6e860c6cf2 Francis Laniel 2021-02-25 427 }
a28a6e860c6cf2 Francis Laniel 2021-02-25 428
:::::: The code at line 387 was first introduced by commit
:::::: f68f2ff91512c199ec24883001245912afc17873 fortify: Detect struct member overflows in memcpy() at compile-time
:::::: TO: Kees Cook <keescook@...omium.org>
:::::: CC: Kees Cook <keescook@...omium.org>
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