linux-kernel - Re: [PATCH v2 3/4] fs: unicode: Use strscpy() instead of strncpy()

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Message-ID: <f6bb5ec3-da94-ae9a-4ac4-e39038b42cb3@collabora.com>
Date:   Thu, 18 Mar 2021 19:43:08 +0530
From:   Shreeya Patel <shreeya.patel@...labora.com>
To:     krisman@...labora.com, jaegeuk@...nel.org, yuchao0@...wei.com,
        tytso@....edu, adilger.kernel@...ger.ca, drosen@...gle.com,
        ebiggers@...gle.com
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        kernel@...labora.com, andre.almeida@...labora.com,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v2 3/4] fs: unicode: Use strscpy() instead of strncpy()


On 18/03/21 7:03 pm, Shreeya Patel wrote:
> Following warning was reported by Kernel Test Robot.
>
> In function 'utf8_parse_version',
> inlined from 'utf8_load' at fs/unicode/utf8mod.c:195:7:
>>> fs/unicode/utf8mod.c:175:2: warning: 'strncpy' specified bound 12 equals
> destination size [-Wstringop-truncation]
> 175 |  strncpy(version_string, version, sizeof(version_string));
>      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> The -Wstringop-truncation warning highlights the unintended
> uses of the strncpy function that truncate the terminating NULL
> character from the source string.
> Unlike strncpy(), strscpy() always null-terminates the destination string,
> hence use strscpy() instead of strncpy().


Not sure if strscpy is preferable. Just found this article 
https://lwn.net/Articles/659214/
Should I go for memcpy instead?


>
> Signed-off-by: Shreeya Patel <shreeya.patel@...labora.com>
> Reported-by: kernel test robot <lkp@...el.com>
> ---
> Changes in v2
>    - Resolve warning of -Wstringop-truncation reported by
>      kernel test robot.
>
>   fs/unicode/unicode-core.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/unicode/unicode-core.c b/fs/unicode/unicode-core.c
> index d5f09e022ac5..287a8a48836c 100644
> --- a/fs/unicode/unicode-core.c
> +++ b/fs/unicode/unicode-core.c
> @@ -179,7 +179,7 @@ static int unicode_parse_version(const char *version, unsigned int *maj,
>   		{0, NULL}
>   	};
>   
> -	strncpy(version_string, version, sizeof(version_string));
> +	strscpy(version_string, version, sizeof(version_string));
>   
>   	if (match_token(version_string, token, args) != 1)
>   		return -EINVAL;