tree: https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git kspp/memcpy/next-20210816/v2 head: 0f0894ea4d0761cc43917960b4878fa3d1ed7a5f commit: 1db8308d772a6ac9744a973ea07cbc811c608c04 [34/63] fortify: Detect struct member overflows in memcpy() at compile-time config: x86_64-allyesconfig (attached as .config) compiler: gcc-9 (Debian 9.3.0-22) 9.3.0 reproduce (this is a W=1 build): # https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git/commit/?id=1db8308d772a6ac9744a973ea07cbc811c608c04 git remote add kees https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git git fetch --no-tags kees kspp/memcpy/next-20210816/v2 git checkout 1db8308d772a6ac9744a973ea07cbc811c608c04 # save the attached .config to linux build tree make W=1 ARCH=x86_64 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot All warnings (new ones prefixed by >>): In file included from include/linux/string.h:253, from include/linux/bitmap.h:10, from include/linux/cpumask.h:12, from arch/x86/include/asm/cpumask.h:5, from arch/x86/include/asm/msr.h:11, from arch/x86/include/asm/processor.h:22, from arch/x86/include/asm/cpufeature.h:5, from arch/x86/include/asm/thread_info.h:53, from include/linux/thread_info.h:60, from arch/x86/include/asm/preempt.h:7, from include/linux/preempt.h:78, from include/linux/spinlock.h:51, from include/linux/wait.h:9, from include/linux/wait_bit.h:8, from include/linux/fs.h:6, from fs/ksmbd/ndr.c:7: In function 'fortify_memcpy_chk', inlined from 'ndr_read_string' at fs/ksmbd/ndr.c:86:2, inlined from 'ndr_decode_dos_attr' at fs/ksmbd/ndr.c:167:2: >> include/linux/fortify-string.h:265:4: warning: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Wattribute-warning] 265 | __write_overflow_field(p_size_field, size); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ vim +/__write_overflow_field +265 include/linux/fortify-string.h 211 212 /* 213 * To make sure the compiler can enforce protection against buffer overflows, 214 * memcpy(), memmove(), and memset() must not be used beyond individual 215 * struct members. If you need to copy across multiple members, please use 216 * struct_group() to create a named mirror of an anonymous struct union. 217 * (e.g. see struct sk_buff.) 218 * 219 * Mitigation coverage 220 * Bounds checking at: 221 * +-------+-------+-------+-------+ 222 * | Compile time | Run time | 223 * memcpy() argument sizes: | write | read | write | read | 224 * +-------+-------+-------+-------+ 225 * memcpy(known, known, constant) | y | y | n/a | n/a | 226 * memcpy(unknown, known, constant) | n | y | V | n/a | 227 * memcpy(known, unknown, constant) | y | n | n/a | V | 228 * memcpy(unknown, unknown, constant) | n | n | V | V | 229 * memcpy(known, known, dynamic) | n | n | b | B | 230 * memcpy(unknown, known, dynamic) | n | n | V | B | 231 * memcpy(known, unknown, dynamic) | n | n | b | V | 232 * memcpy(unknown, unknown, dynamic) | n | n | V | V | 233 * +-------+-------+-------+-------+ 234 * 235 * y = deterministic compile-time bounds checking 236 * n = cannot do deterministic compile-time bounds checking 237 * n/a = no run-time bounds checking needed since compile-time deterministic 238 * b = perform run-time bounds checking 239 * B = can perform run-time bounds checking, but current unenforced 240 * V = vulnerable to run-time overflow 241 * 242 */ 243 __FORTIFY_INLINE void fortify_memcpy_chk(__kernel_size_t size, 244 const size_t p_size, 245 const size_t q_size, 246 const size_t p_size_field, 247 const size_t q_size_field, 248 const char *func) 249 { 250 if (__builtin_constant_p(size)) { 251 /* 252 * Length argument is a constant expression, so we 253 * can perform compile-time bounds checking where 254 * buffer sizes are known. 255 */ 256 257 /* Error when size is larger than enclosing struct. */ 258 if (p_size > p_size_field && p_size < size) 259 __write_overflow(); 260 if (q_size > q_size_field && q_size < size) 261 __read_overflow2(); 262 263 /* Warn when write size argument larger than dest field. */ 264 if (p_size_field < size) > 265 __write_overflow_field(p_size_field, size); 266 /* 267 * Warn for source field over-read when building with W=1 268 * or when an over-write happened, so both can be fixed at 269 * the same time. 270 */ 271 if ((IS_ENABLED(KBUILD_EXTRA_WARN1) || p_size_field < size) && 272 q_size_field < size) 273 __read_overflow2_field(q_size_field, size); 274 } 275 /* 276 * At this point, length argument may not be a constant expression, 277 * so run-time bounds checking can be done where buffer sizes are 278 * known. (This is not an "else" because the above checks may only 279 * be compile-time warnings, and we want to still warn for run-time 280 * overflows.) 281 */ 282 283 /* 284 * Always stop accesses beyond the struct that contains the 285 * field, when the buffer's remaining size is known. 286 * (The -1 test is to optimize away checks where the buffer 287 * lengths are unknown.) 288 */ 289 if ((p_size != (size_t)(-1) && p_size < size) || 290 (q_size != (size_t)(-1) && q_size < size)) 291 fortify_panic(func); 292 } 293 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org