linux-kernel - Re: [PATCH 2/6] lib/string: Fix erroneous 'overflow' documentation

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Message-ID: <CAGXu5jJcf8S3vS5d7B9oC2V7F6Gjbeu5vUCQiAFXTzeXcrno0w@mail.gmail.com>
Date:   Wed, 20 Feb 2019 16:02:37 -0800
From:   Kees Cook <keescook@...omium.org>
To:     "Tobin C. Harding" <tobin@...nel.org>
Cc:     Shuah Khan <shuah@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/6] lib/string: Fix erroneous 'overflow' documentation

On Mon, Feb 18, 2019 at 3:24 PM Tobin C. Harding <tobin@...nel.org> wrote:
>
> Current documentation uses 'overflow' to describe a situation where less
> data is written to a buffer than buffer size not more.  'overflow' is
> the wrong word here - since we don't typically say 'underflow' change
> the whole sentence.
>
> Fix erroneous 'overflow' documentation for under filled buffer.
>
> Signed-off-by: Tobin C. Harding <tobin@...nel.org>
> ---
>  lib/string.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/lib/string.c b/lib/string.c
> index 38e4ca08e757..7f1d72db53c5 100644
> --- a/lib/string.c
> +++ b/lib/string.c
> @@ -173,8 +173,8 @@ EXPORT_SYMBOL(strlcpy);
>   *
>   * Preferred to strncpy() since it always returns a valid string, and
>   * doesn't unnecessarily force the tail of the destination buffer to be
> - * zeroed.  If the zeroing is desired, it's likely cleaner to use strscpy()
> - * with an overflow test, then just memset() the tail of the dest buffer.
> + * zeroed.  If the zeroing is desired, it's likely cleaner to use strscpy(),
> + * check the return size, then just memset() the tail of the dest buffer.
>   */

I'd just fold this patch into the strscpy_zeroed() patch. No need for
a kind of "no op" change here when we'll just change it again with a
better advice ("use strscpy_zeroed()!")

-- 
Kees Cook