Re: [PATCH] block/compat_ioctl: fix range check in BLKGETSIZE

[Khazhismel Kumykov]

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On Fri, Apr 6, 2018 at 3:23 PM, Khazhismel Kumykov <khazhy@xxxxxxxxxx> wrote:
> kernel ulong and compat_ulong_t may not be same width. Use type directly
> to eliminate mismatches.
>
> This would result in truncation rather than EFBIG for 32bit mode for
> large disks.
>
> Signed-off-by: Khazhismel Kumykov <khazhy@xxxxxxxxxx>
> ---
>  block/compat_ioctl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/block/compat_ioctl.c b/block/compat_ioctl.c
> index 6ca015f92766..3a2c77f07da8 100644
> --- a/block/compat_ioctl.c
> +++ b/block/compat_ioctl.c
> @@ -388,7 +388,7 @@ long compat_blkdev_ioctl(struct file *file, unsigned cmd, unsigned long arg)
>                 return 0;
>         case BLKGETSIZE:
>                 size = i_size_read(bdev->bd_inode);
> -               if ((size >> 9) > ~0UL)
> +               if ((size >> 9) > ~((compat_ulong_t)0UL))
>                         return -EFBIG;
>                 return compat_put_ulong(arg, size >> 9);
>
> --
> 2.17.0.484.g0c8726318c-goog
>

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