[kees:kspp/memcpy/next-20210816/v2 34/63] 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()?

[kernel test robot <lkp@intel.com>]

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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 <lkp@intel.com>

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	

---
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https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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