Re: [PATCH v4 2/8] lib: add "on" and "off" to strtobool

From: Joe Perches
Date: Tue Jan 19 2016 - 21:09:54 EST


On Tue, 2016-01-19 at 10:08 -0800, Kees Cook wrote:
> Several places in the kernel expect to use "on" and "off" for their
> boolean signifiers, so add them to strtobool.

Several places in the kernel use a char address like
fs/cifs/cifs_debug.c


char c;
...


if (strtobool(&c, ...))

Using s[1] might cause problems for those uses.
> diff --git a/lib/string.c b/lib/string.c
[]
> @@ -635,12 +635,15 @@ EXPORT_SYMBOL(sysfs_streq);
>   * @s: input string
>   * @res: result
>   *
> - * This routine returns 0 iff the first character is one of 'Yy1Nn0'.
> - * Otherwise it will return -EINVAL.  Value pointed to by res is
> - * updated upon finding a match.
> + * This routine returns 0 iff the first character is one of 'Yy1Nn0', or
> + * [oO][NnFf] for "on" and "off". Otherwise it will return -EINVAL.  Value
> + * pointed to by res is updated upon finding a match.
>   */
>  int strtobool(const char *s, bool *res)
>  {
> + if (!s)
> + return -EINVAL;
> +
>   switch (s[0]) {
>   case 'y':
>   case 'Y':
> @@ -652,6 +655,21 @@ int strtobool(const char *s, bool *res)
>   case '0':
>   *res = false;
>   break;
> + case 'o':
> + case 'O':
> + switch (s[1]) {
> + case 'n':
> + case 'N':
> + *res = true;
> + break;
> + case 'f':
> + case 'F':

Perhaps
switch (tolower(s[1])) {
is more readable

> + *res = false;
> + break;
> + default:
> + return -EINVAL;
> + }
> + break;

or maybe /* fallthrough */

>   default:
>   return -EINVAL;
>   }