linux-kernel - Re: [PATCH] kdb: Fix bound check compiler warning

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Message-ID: <20190508081640.tvtnazr4tf5jijh7@holly.lan>
Date:   Wed, 8 May 2019 09:16:40 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Wenlin Kang <wenlin.kang@...driver.com>
Cc:     jason.wessel@...driver.com, prarit@...hat.com,
        kgdb-bugreport@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kdb: Fix bound check compiler warning

On Wed, May 08, 2019 at 09:52:39AM +0800, Wenlin Kang wrote:
> The strncpy() function may leave the destination string buffer
> unterminated, better use strlcpy() instead.
> 
> This fixes the following warning with gcc 8.2:
> 
> kernel/debug/kdb/kdb_io.c: In function 'kdb_getstr':
> kernel/debug/kdb/kdb_io.c:449:3: warning: 'strncpy' specified bound 256 equals destination size [-Wstringop-truncation]
>    strncpy(kdb_prompt_str, prompt, CMD_BUFLEN);
>    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Signed-off-by: Wenlin Kang <wenlin.kang@...driver.com>
> ---
>  kernel/debug/kdb/kdb_io.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c
> index 6a4b414..7fd4513 100644
> --- a/kernel/debug/kdb/kdb_io.c
> +++ b/kernel/debug/kdb/kdb_io.c
> @@ -446,7 +446,7 @@ static char *kdb_read(char *buffer, size_t bufsize)
>  char *kdb_getstr(char *buffer, size_t bufsize, const char *prompt)
>  {
>  	if (prompt && kdb_prompt_str != prompt)
> -		strncpy(kdb_prompt_str, prompt, CMD_BUFLEN);
> +		strlcpy(kdb_prompt_str, prompt, CMD_BUFLEN);

Shouldn't that be strscpy?


Daniel.

>  	kdb_printf(kdb_prompt_str);
>  	kdb_nextline = 1;	/* Prompt and input resets line number */
>  	return kdb_read(buffer, bufsize);
> -- 
> 1.9.1
>