linux-kernel - Re: [PATCH] lib/string: Introduce sysfs

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Date:   Fri, 2 Apr 2021 11:17:13 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Gioh Kim <gi-oh.kim@...os.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, jinpu.wang@...os.com,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH] lib/string: Introduce sysfs_streqcase

Thanks for the patch!

+ akpm (please remember to run ./scripts/get_maintainer.pl on your patch files)

On Fri, Apr 2, 2021 at 2:41 AM Gioh Kim <gi-oh.kim@...os.com> wrote:
>
> As the name shows, it checks if strings are equal in case insensitive
> manner. I found some cases using strncasecmp to check the entire
> strings and they would not work as intended.
>
> For example, drivers/infiniband/ulp/rtrs/rtrs-clt-sysfs.c uses
> strncasecmp to check that the input via sysfs is "mi". But it would
> work even-if the input is "min-wrongcommand".
> And also drivers/pnp/interface.c checks "disable" command with
> strncasecmp but it would also work if the command is "disable-wrong".

Perhaps those callers should be using strcasecmp then, rather than strncasecmp?

Also, if they're being liberal in accepting either case, I don't see
why the sysfs nodes should be strict in rejecting trailing input at
that point.

>
> Signed-off-by: Gioh Kim <gi-oh.kim@...os.com>
> ---
>  lib/string.c | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
>
> diff --git a/lib/string.c b/lib/string.c
> index 7548eb715ddb..5e6bc0d3d5c6 100644
> --- a/lib/string.c
> +++ b/lib/string.c
> @@ -714,6 +714,29 @@ bool sysfs_streq(const char *s1, const char *s2)
>  }
>  EXPORT_SYMBOL(sysfs_streq);
>
> +/**
> + * sysfs_streqcase - same to sysfs_streq and case insensitive
> + * @s1: one string
> + * @s2: another string
> + *
> + */
> +bool sysfs_streqcase(const char *s1, const char *s2)
> +{
> +       while (*s1 && tolower(*s1) == tolower(*s2)) {
> +               s1++;
> +               s2++;
> +       }
> +
> +       if (*s1 == *s2)
> +               return true;
> +       if (!*s1 && *s2 == '\n' && !s2[1])
> +               return true;
> +       if (*s1 == '\n' && !s1[1] && !*s2)
> +               return true;
> +       return false;
> +}
> +EXPORT_SYMBOL(sysfs_streqcase);

This should be declared in
include/linux/string.h
in order for others to use this (as 0day bot notes).

> +
>  /**
>   * match_string - matches given string in an array
>   * @array:     array of strings
> --
> 2.25.1
>


--
Thanks,
~Nick Desaulniers