linux-kernel - Re: [greybus-dev] [PATCH] greybus: remove stray nul byte in apb_log_enable

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Date:   Fri, 26 Mar 2021 11:31:20 -0500
From:   Alex Elder <elder@...aro.org>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Johan Hovold <johan@...nel.org>, Alex Elder <elder@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     greybus-dev@...ts.linaro.org, linux-kernel@...r.kernel.org
Subject: Re: [greybus-dev] [PATCH] greybus: remove stray nul byte in
 apb_log_enable_read output

On 3/26/21 10:22 AM, Rasmus Villemoes wrote:
> Including a nul byte in the otherwise human-readable ascii output
> from this debugfs file is probably not intended.

Looking only at the comments above simple_read_from_buffer(),
the last argument is the size of the buffer (tmp_buf in this
case).  So "3" is proper.

But looking at callers, it seems that the trailing NUL is
often excluded this way.

I don't really have a problem with your patch, but could
you explain why having the NUL byte included is an actual
problem?  A short statement about that would provide better
context than just "probably not intended."

Thanks.

					-Alex
> 
> Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
> ---
>   drivers/greybus/es2.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/greybus/es2.c b/drivers/greybus/es2.c
> index 48ad154df3a7..86a7fbc7fe13 100644
> --- a/drivers/greybus/es2.c
> +++ b/drivers/greybus/es2.c
> @@ -1171,7 +1171,7 @@ static ssize_t apb_log_enable_read(struct file *f, char __user *buf,
>   	char tmp_buf[3];
>   
>   	sprintf(tmp_buf, "%d\n", enable);
> -	return simple_read_from_buffer(buf, count, ppos, tmp_buf, 3);
> +	return simple_read_from_buffer(buf, count, ppos, tmp_buf, 2);
>   }
>   
>   static ssize_t apb_log_enable_write(struct file *f, const char __user *buf,
>