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

From: Dan Carpenter
Date: Tue Jul 12 2022 - 10:35:31 EST


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@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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