linux-kernel - Re: [PATCH 08/11] blktrace: convert strncpy() to strscpy

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Message-ID: <20240328101422.37e1c4f0@gandalf.local.home>
Date: Thu, 28 Mar 2024 10:14:22 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Arnd Bergmann <arnd@...nel.org>
Cc: linux-kernel@...r.kernel.org, Jens Axboe <axboe@...nel.dk>, Masami
 Hiramatsu <mhiramat@...nel.org>, Arnd Bergmann <arnd@...db.de>, Mathieu
 Desnoyers <mathieu.desnoyers@...icios.com>, linux-block@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH 08/11] blktrace: convert strncpy() to strscpy_pad()

On Thu, 28 Mar 2024 15:04:52 +0100
Arnd Bergmann <arnd@...nel.org> wrote:

> From: Arnd Bergmann <arnd@...db.de>
> 
> gcc-9 warns about a possibly non-terminated string copy:
> 
> kernel/trace/blktrace.c: In function 'do_blk_trace_setup':
> kernel/trace/blktrace.c:527:2: error: 'strncpy' specified bound 32 equals destination size [-Werror=stringop-truncation]
> 
> Newer versions are fine here because they see the following explicit
> nul-termination. Using strscpy_pad() avoids the warning and
> simplifies the code a little. The padding helps  give a clean
> buffer to userspace.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  kernel/trace/blktrace.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
> index d5d94510afd3..95a00160d465 100644
> --- a/kernel/trace/blktrace.c
> +++ b/kernel/trace/blktrace.c
> @@ -524,8 +524,7 @@ static int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
>  	if (!buts->buf_size || !buts->buf_nr)
>  		return -EINVAL;
>  
> -	strncpy(buts->name, name, BLKTRACE_BDEV_SIZE);
> -	buts->name[BLKTRACE_BDEV_SIZE - 1] = '\0';
> +	strscpy(buts->name, name, BLKTRACE_BDEV_SIZE);

The commit message says "Using strscpy_pad()" but it doesn't do so in the
patch.

Rule 12 of debugging: "When the comment and the code do not match, they are
                       probably both wrong"

-- Steve


>  
>  	/*
>  	 * some device names have larger paths - convert the slashes