Re: [PATCH] vfio/mlx5: clean up overflow check

[kernel test robot]

Hi Dan,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on awilliam-vfio/next]
[also build test WARNING on rdma/for-next linus/master v5.19-rc5 next-20220707]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Dan-Carpenter/vfio-mlx5-clean-up-overflow-check/20220707-225657
base:   https://github.com/awilliam/linux-vfio.git next
config: i386-allyesconfig (https://download.01.org/0day-ci/archive/20220708/202207080331.FTVSHxW8-lkp@xxxxxxxxx/config)
compiler: gcc-11 (Debian 11.3.0-3) 11.3.0
reproduce (this is a W=1 build):
        # https://github.com/intel-lab-lkp/linux/commit/44607f8f3817e1af6622db7d70ad5bc457b8f203
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Dan-Carpenter/vfio-mlx5-clean-up-overflow-check/20220707-225657
        git checkout 44607f8f3817e1af6622db7d70ad5bc457b8f203
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash drivers/vfio/pci/mlx5/

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@xxxxxxxxx>

All warnings (new ones prefixed by >>):

   In file included from include/linux/device.h:29,
                    from drivers/vfio/pci/mlx5/main.c:6:
   drivers/vfio/pci/mlx5/main.c: In function 'mlx5vf_resume_write':
>> include/linux/overflow.h:67:22: warning: comparison of distinct pointer types lacks a cast
      67 |         (void) (&__a == &__b);                  \
         |                      ^~
   drivers/vfio/pci/mlx5/main.c:282:13: note: in expansion of macro 'check_add_overflow'
     282 |             check_add_overflow(len, (unsigned long)*pos, &requested_length))
         |             ^~~~~~~~~~~~~~~~~~
   include/linux/overflow.h:68:22: warning: comparison of distinct pointer types lacks a cast
      68 |         (void) (&__a == __d);                   \
         |                      ^~
   drivers/vfio/pci/mlx5/main.c:282:13: note: in expansion of macro 'check_add_overflow'
     282 |             check_add_overflow(len, (unsigned long)*pos, &requested_length))
         |             ^~~~~~~~~~~~~~~~~~


vim +67 include/linux/overflow.h

9b80e4c4ddaca35 Kees Cook        2020-08-12  54  
f0907827a8a9152 Rasmus Villemoes 2018-05-08  55  /*
f0907827a8a9152 Rasmus Villemoes 2018-05-08  56   * For simplicity and code hygiene, the fallback code below insists on
f0907827a8a9152 Rasmus Villemoes 2018-05-08  57   * a, b and *d having the same type (similar to the min() and max()
f0907827a8a9152 Rasmus Villemoes 2018-05-08  58   * macros), whereas gcc's type-generic overflow checkers accept
f0907827a8a9152 Rasmus Villemoes 2018-05-08  59   * different types. Hence we don't just make check_add_overflow an
f0907827a8a9152 Rasmus Villemoes 2018-05-08  60   * alias for __builtin_add_overflow, but add type checks similar to
f0907827a8a9152 Rasmus Villemoes 2018-05-08  61   * below.
f0907827a8a9152 Rasmus Villemoes 2018-05-08  62   */
9b80e4c4ddaca35 Kees Cook        2020-08-12  63  #define check_add_overflow(a, b, d) __must_check_overflow(({	\
f0907827a8a9152 Rasmus Villemoes 2018-05-08  64  	typeof(a) __a = (a);			\
f0907827a8a9152 Rasmus Villemoes 2018-05-08  65  	typeof(b) __b = (b);			\
f0907827a8a9152 Rasmus Villemoes 2018-05-08  66  	typeof(d) __d = (d);			\
f0907827a8a9152 Rasmus Villemoes 2018-05-08 @67  	(void) (&__a == &__b);			\
f0907827a8a9152 Rasmus Villemoes 2018-05-08  68  	(void) (&__a == __d);			\
f0907827a8a9152 Rasmus Villemoes 2018-05-08  69  	__builtin_add_overflow(__a, __b, __d);	\
9b80e4c4ddaca35 Kees Cook        2020-08-12  70  }))
f0907827a8a9152 Rasmus Villemoes 2018-05-08  71  

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