linux-kernel - include/linux/sunrpc/xdr.h:734:10: warning: result of comparison of constant 4611686018427387903 with expression of type '__u32' (aka 'unsigned int') is always false

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Message-ID: <202203260009.5SM2MiP9-lkp@intel.com>
Date:   Sat, 26 Mar 2022 01:27:08 +0800
From:   kernel test robot <lkp@...el.com>
To:     Dan Carpenter <error27@...il.com>
Cc:     llvm@...ts.linux.dev, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org, Chuck Lever <chuck.lever@...cle.com>
Subject: include/linux/sunrpc/xdr.h:734:10: warning: result of comparison of
 constant 4611686018427387903 with expression of type '__u32' (aka 'unsigned
 int') is always false

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   34af78c4e616c359ed428d79fe4758a35d2c5473
commit: 23a9dbbe0faf124fc4c139615633b9d12a3a89ef NFSD: prevent integer overflow on 32 bit systems
date:   10 days ago
config: x86_64-randconfig-a012 (https://download.01.org/0day-ci/archive/20220326/202203260009.5SM2MiP9-lkp@intel.com/config)
compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project 0f6d9501cf49ce02937099350d08f20c4af86f3d)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=23a9dbbe0faf124fc4c139615633b9d12a3a89ef
        git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
        git fetch --no-tags linus master
        git checkout 23a9dbbe0faf124fc4c139615633b9d12a3a89ef
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash net/sunrpc/auth_gss/

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 net/sunrpc/auth_gss/gss_generic_token.c:37:
   In file included from include/linux/sunrpc/sched.h:19:
>> include/linux/sunrpc/xdr.h:734:10: warning: result of comparison of constant 4611686018427387903 with expression of type '__u32' (aka 'unsigned int') is always false [-Wtautological-constant-out-of-range-compare]
           if (len > SIZE_MAX / sizeof(*p))
               ~~~ ^ ~~~~~~~~~~~~~~~~~~~~~
   1 warning generated.


vim +734 include/linux/sunrpc/xdr.h

   712	
   713	/**
   714	 * xdr_stream_decode_uint32_array - Decode variable length array of integers
   715	 * @xdr: pointer to xdr_stream
   716	 * @array: location to store the integer array or NULL
   717	 * @array_size: number of elements to store
   718	 *
   719	 * Return values:
   720	 *   On success, returns number of elements stored in @array
   721	 *   %-EBADMSG on XDR buffer overflow
   722	 *   %-EMSGSIZE if the size of the array exceeds @array_size
   723	 */
   724	static inline ssize_t
   725	xdr_stream_decode_uint32_array(struct xdr_stream *xdr,
   726			__u32 *array, size_t array_size)
   727	{
   728		__be32 *p;
   729		__u32 len;
   730		ssize_t retval;
   731	
   732		if (unlikely(xdr_stream_decode_u32(xdr, &len) < 0))
   733			return -EBADMSG;
 > 734		if (len > SIZE_MAX / sizeof(*p))
   735			return -EBADMSG;
   736		p = xdr_inline_decode(xdr, len * sizeof(*p));
   737		if (unlikely(!p))
   738			return -EBADMSG;
   739		if (array == NULL)
   740			return len;
   741		if (len <= array_size) {
   742			if (len < array_size)
   743				memset(array+len, 0, (array_size-len)*sizeof(*array));
   744			array_size = len;
   745			retval = len;
   746		} else
   747			retval = -EMSGSIZE;
   748		for (; array_size > 0; p++, array++, array_size--)
   749			*array = be32_to_cpup(p);
   750		return retval;
   751	}
   752	

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