Re: [PATCH 1/2] staging: lustre: lprocfs: Use kstrtouint_from_user

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Thu, May 04, 2017 at 12:13:38PM -0400, Mathias Rav wrote:
> Prefer kstrtouint_from_user to copy_from_user+simple_strtoul.
> 
> The helper function lprocfs_wr_uint() is only used to implement
> "dump_granted_max" in debugfs.
> 
> Note the slight change in semantics: The previous implementation using
> simple_strtoul allows garbage after the number, whereas kstrtox only allows
> a trailing line break. The previous implementation allowed a write of zero
> bytes whereas kstrtox will return -EINVAL. Since this only affects a single
> debugfs endpoint, this should be a permissible slight change of semantics
> in exchange for 18 fewer lines of code.
> 
> Signed-off-by: Mathias Rav <mathiasrav@gmail.com>
> ---
>  .../lustre/lustre/obdclass/lprocfs_status.c        | 22 +---------------------
>  1 file changed, 1 insertion(+), 21 deletions(-)
> 
> diff --git a/drivers/staging/lustre/lustre/obdclass/lprocfs_status.c b/drivers/staging/lustre/lustre/obdclass/lprocfs_status.c
> index 1ec6e3767d81..338ce34d6514 100644
> --- a/drivers/staging/lustre/lustre/obdclass/lprocfs_status.c
> +++ b/drivers/staging/lustre/lustre/obdclass/lprocfs_status.c
> @@ -399,27 +399,7 @@ EXPORT_SYMBOL(lprocfs_rd_uint);
>  int lprocfs_wr_uint(struct file *file, const char __user *buffer,
>  		    unsigned long count, void *data)
>  {
> -	unsigned *p = data;
> -	char dummy[MAX_STRING_SIZE + 1], *end;
> -	unsigned long tmp;
> -
> -	if (count >= sizeof(dummy))
> -		return -EINVAL;
> -
> -	if (count == 0)
> -		return 0;
> -
> -	if (copy_from_user(dummy, buffer, count))
> -		return -EFAULT;
> -
> -	dummy[count] = '\0';
> -
> -	tmp = simple_strtoul(dummy, &end, 0);
> -	if (dummy == end)
> -		return -EINVAL;
> -
> -	*p = (unsigned int)tmp;
> -	return count;
> +	return kstrtouint_from_user(buffer, count, 0, (unsigned int *)data);

Why not just delete this whole function and have the callers make this
call instead?  No need for unneeded wrapper functions of core kernel
calls.

thanks,

greg k-h