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

[Dan Carpenter <dan.carpenter@oracle.com>]

Sorry for these!  I need to resend, of course.  I'm sligtly delayed
because it was a three day weekend.  I will try do that tomorrow.

regards,
dan carpenter

On Fri, Jul 08, 2022 at 03:37:32AM +0800, kernel test robot wrote:
> 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@intel.com/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@intel.com>
> 
> 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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