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Message-ID: <202203281242.c13N4CDX-lkp@intel.com>
Date: Mon, 28 Mar 2022 12:15:44 +0800
From: kernel test robot <lkp@...el.com>
To: Kees Cook <keescook@...omium.org>
Cc: kbuild-all@...ts.01.org, linux-kernel@...r.kernel.org
Subject: include/linux/fortify-string.h:267:4: warning: call to
'__write_overflow_field' declared with attribute warning: detected write
beyond size of field (1st parameter); maybe use struct_group()?
tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head: ae085d7f9365de7da27ab5c0d16b12d51ea7fca9
commit: f68f2ff91512c199ec24883001245912afc17873 fortify: Detect struct member overflows in memcpy() at compile-time
date: 6 weeks ago
config: i386-buildonly-randconfig-r001-20220328 (https://download.01.org/0day-ci/archive/20220328/202203281242.c13N4CDX-lkp@intel.com/config)
compiler: gcc-9 (Ubuntu 9.4.0-1ubuntu1~20.04.1) 9.4.0
reproduce (this is a W=1 build):
# https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f68f2ff91512c199ec24883001245912afc17873
git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
git fetch --no-tags linus master
git checkout f68f2ff91512c199ec24883001245912afc17873
# save the config file to linux build tree
mkdir build_dir
make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash net/ipv4/
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@...el.com>
All warnings (new ones prefixed by >>):
In file included from include/linux/string.h:253,
from arch/x86/include/asm/page_32.h:22,
from arch/x86/include/asm/page.h:14,
from arch/x86/include/asm/thread_info.h:12,
from include/linux/thread_info.h:60,
from arch/x86/include/asm/preempt.h:7,
from include/linux/preempt.h:78,
from include/linux/bottom_half.h:6,
from net/ipv4/tcp_ipv4.c:50:
In function 'fortify_memcpy_chk',
inlined from 'tcp_md5_do_add' at net/ipv4/tcp_ipv4.c:1204:2:
>> include/linux/fortify-string.h:267:4: warning: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Wattribute-warning]
267 | __write_overflow_field(p_size_field, size);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
vim +/__write_overflow_field +267 include/linux/fortify-string.h
213
214 /*
215 * To make sure the compiler can enforce protection against buffer overflows,
216 * memcpy(), memmove(), and memset() must not be used beyond individual
217 * struct members. If you need to copy across multiple members, please use
218 * struct_group() to create a named mirror of an anonymous struct union.
219 * (e.g. see struct sk_buff.) Read overflow checking is currently only
220 * done when a write overflow is also present, or when building with W=1.
221 *
222 * Mitigation coverage matrix
223 * Bounds checking at:
224 * +-------+-------+-------+-------+
225 * | Compile time | Run time |
226 * memcpy() argument sizes: | write | read | write | read |
227 * dest source length +-------+-------+-------+-------+
228 * memcpy(known, known, constant) | y | y | n/a | n/a |
229 * memcpy(known, unknown, constant) | y | n | n/a | V |
230 * memcpy(known, known, dynamic) | n | n | B | B |
231 * memcpy(known, unknown, dynamic) | n | n | B | V |
232 * memcpy(unknown, known, constant) | n | y | V | n/a |
233 * memcpy(unknown, unknown, constant) | n | n | V | V |
234 * memcpy(unknown, known, dynamic) | n | n | V | B |
235 * memcpy(unknown, unknown, dynamic) | n | n | V | V |
236 * +-------+-------+-------+-------+
237 *
238 * y = perform deterministic compile-time bounds checking
239 * n = cannot perform deterministic compile-time bounds checking
240 * n/a = no run-time bounds checking needed since compile-time deterministic
241 * B = can perform run-time bounds checking (currently unimplemented)
242 * V = vulnerable to run-time overflow (will need refactoring to solve)
243 *
244 */
245 __FORTIFY_INLINE void fortify_memcpy_chk(__kernel_size_t size,
246 const size_t p_size,
247 const size_t q_size,
248 const size_t p_size_field,
249 const size_t q_size_field,
250 const char *func)
251 {
252 if (__builtin_constant_p(size)) {
253 /*
254 * Length argument is a constant expression, so we
255 * can perform compile-time bounds checking where
256 * buffer sizes are known.
257 */
258
259 /* Error when size is larger than enclosing struct. */
260 if (p_size > p_size_field && p_size < size)
261 __write_overflow();
262 if (q_size > q_size_field && q_size < size)
263 __read_overflow2();
264
265 /* Warn when write size argument larger than dest field. */
266 if (p_size_field < size)
> 267 __write_overflow_field(p_size_field, size);
268 /*
269 * Warn for source field over-read when building with W=1
270 * or when an over-write happened, so both can be fixed at
271 * the same time.
272 */
273 if ((IS_ENABLED(KBUILD_EXTRA_WARN1) || p_size_field < size) &&
274 q_size_field < size)
275 __read_overflow2_field(q_size_field, size);
276 }
277 /*
278 * At this point, length argument may not be a constant expression,
279 * so run-time bounds checking can be done where buffer sizes are
280 * known. (This is not an "else" because the above checks may only
281 * be compile-time warnings, and we want to still warn for run-time
282 * overflows.)
283 */
284
285 /*
286 * Always stop accesses beyond the struct that contains the
287 * field, when the buffer's remaining size is known.
288 * (The -1 test is to optimize away checks where the buffer
289 * lengths are unknown.)
290 */
291 if ((p_size != (size_t)(-1) && p_size < size) ||
292 (q_size != (size_t)(-1) && q_size < size))
293 fortify_panic(func);
294 }
295
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0-DAY CI Kernel Test Service
https://01.org/lkp
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