linux-kernel - Re: [kees:for-next/lkdtm 6/6] drivers/misc/lkdtm/cfi.c:62:37: warning: cast from pointer to integer of different size

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Date:   Mon, 18 Apr 2022 15:25:47 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Dan Li <ashimida@...ux.alibaba.com>
Cc:     kbuild-all@...ts.01.org, linux-kernel@...r.kernel.org,
        kernel test robot <lkp@...el.com>
Subject: Re: [kees:for-next/lkdtm 6/6] drivers/misc/lkdtm/cfi.c:62:37:
 warning: cast from pointer to integer of different size

On Sun, Apr 17, 2022 at 07:26:33AM +0800, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git for-next/lkdtm
> head:   2e53b877dc1258d4ac3de98f496bb88ec3bf5e25
> commit: 2e53b877dc1258d4ac3de98f496bb88ec3bf5e25 [6/6] lkdtm: Add CFI_BACKWARD to test ROP mitigations
> config: sparc-randconfig-r026-20220417 (https://download.01.org/0day-ci/archive/20220417/202204170710.LwCV5Ec0-lkp@intel.com/config)
> compiler: sparc-linux-gcc (GCC) 11.2.0
> 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/kees/linux.git/commit/?id=2e53b877dc1258d4ac3de98f496bb88ec3bf5e25
>         git remote add kees https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git
>         git fetch --no-tags kees for-next/lkdtm
>         git checkout 2e53b877dc1258d4ac3de98f496bb88ec3bf5e25
>         # save the config file to linux build tree
>         mkdir build_dir
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=sparc SHELL=/bin/bash drivers/misc/lkdtm/
> 
> 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 >>):
> 
>    drivers/misc/lkdtm/cfi.c: In function 'set_return_addr_unchecked':
> >> drivers/misc/lkdtm/cfi.c:62:37: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
>       62 |         ((__force __typeof__(addr))((__force u64)(addr) | PAGE_OFFSET))
>          |                                     ^
>    drivers/misc/lkdtm/cfi.c:72:13: note: in expansion of macro 'no_pac_addr'
>       72 |         if (no_pac_addr(*ret_addr) == expected)
>          |             ^~~~~~~~~~~

Hmm. I don't see why this is warning. The macro looks like untagged_addr():

#define untagged_addr(addr)     ({ \
        u64 __addr = (__force u64)(addr); \
        __addr &= __untagged_addr(__addr); \
        (__force __typeof__(addr))__addr; \
})


-- 
Kees Cook