linux-kernel - [linux-stable-rc:linux-5.15.y 4665/5978] 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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Date:   Sat, 23 Apr 2022 15:30:14 +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,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Chuck Lever <chuck.lever@...cle.com>
Subject: [linux-stable-rc:linux-5.15.y 4665/5978]
 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/stable/linux-stable-rc.git linux-5.15.y
head:   81d8d30c35edf29c5c70186ccb14dac4a5ca38a8
commit: 303cd6173dce0a28d26526c77814eb90a41bd898 [4665/5978] NFSD: prevent integer overflow on 32 bit systems
config: x86_64-randconfig-a005 (https://download.01.org/0day-ci/archive/20220423/202204231526.ijyYsWuP-lkp@intel.com/config)
compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project bac6cd5bf85669e3376610cfc4c4f9ca015e7b9b)
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/stable/linux-stable-rc.git/commit/?id=303cd6173dce0a28d26526c77814eb90a41bd898
        git remote add linux-stable-rc https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git
        git fetch --no-tags linux-stable-rc linux-5.15.y
        git checkout 303cd6173dce0a28d26526c77814eb90a41bd898
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash

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/ipv4/ipconfig.c:59:
   In file included from include/linux/nfs_fs.h:31:
   In file included from include/linux/sunrpc/auth.h:13:
   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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