linux-kernel - Re: [PATCH v3 1/5] fs: unicode: Use strscpy() instead of strncpy()

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Message-ID: <87wntxd6we.fsf@collabora.com>
Date:   Tue, 23 Mar 2021 15:09:05 -0400
From:   Gabriel Krisman Bertazi <krisman@...labora.com>
To:     Shreeya Patel <shreeya.patel@...labora.com>
Cc:     tytso@....edu, adilger.kernel@...ger.ca, jaegeuk@...nel.org,
        chao@...nel.org, ebiggers@...gle.com, drosen@...gle.com,
        ebiggers@...nel.org, yuchao0@...wei.com,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-fsdevel@...r.kernel.org, kernel@...labora.com,
        andre.almeida@...labora.com, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v3 1/5] fs: unicode: Use strscpy() instead of strncpy()

Shreeya Patel <shreeya.patel@...labora.com> writes:

> 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().
>
> Fixes: 9d53690f0d4e5 (unicode: implement higher level API for string handling)
> Signed-off-by: Shreeya Patel <shreeya.patel@...labora.com>
> Reported-by: kernel test robot <lkp@...el.com>
> ---
>
> Changes in v3
>   - Return error if strscpy() returns value < 0
>
> Changes in v2
>   - Resolve warning of -Wstringop-truncation reported by
>     kernel test robot.
>
>  fs/unicode/utf8-core.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>

Hi Shreeya,

Thanks for fixing this.

> diff --git a/fs/unicode/utf8-core.c b/fs/unicode/utf8-core.c
> index dc25823bf..706f086bb 100644
> --- a/fs/unicode/utf8-core.c
> +++ b/fs/unicode/utf8-core.c
> @@ -180,7 +180,10 @@ static int utf8_parse_version(const char *version, unsigned int *maj,
>  		{0, NULL}
>  	};
>  
> -	strncpy(version_string, version, sizeof(version_string));
> +	int ret = strscpy(version_string, version, sizeof(version_string));

Usually, no spaces between variable declarations

Other than that,

Acked-by: Gabriel Krisman Bertazi <krisman@...labora.com>

> +
> +	if (ret < 0)
> +		return ret;
>  	if (match_token(version_string, token, args) != 1)
>  		return -EINVAL;

-- 
Gabriel Krisman Bertazi