Re: [PATCH] trace-cmd: Have tracecmd_msg_data_send() return zero on zero size

[Slavomir Kaslev <kaslevs@vmware.com>]

On Thu, 2019-03-21 at 19:41 -0400, Steven Rostedt wrote:
> From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
> 
> If tracecmd_msg_data_send() is passed a size of zero, the loop is not
> entered, nothing is sent, but the ret variable is not initialized and
> garbage can be sent out. The option code can call this with a size of
> zero,
> which can cause an error report.
> 
> Just don't do anything in this case, and return a success.
> 
> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> ---
>  tracecmd/trace-msg.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/tracecmd/trace-msg.c b/tracecmd/trace-msg.c
> index 51d0ac8b..382bd766 100644
> --- a/tracecmd/trace-msg.c
> +++ b/tracecmd/trace-msg.c
> @@ -590,6 +590,10 @@ int tracecmd_msg_data_send(struct
> tracecmd_msg_handle *msg_handle,
>  	int ret;
>  	int count = 0;
>  
> +	/* Don't bother doing anything if there's nothing to do */
> +	if (!size)
> +		return 0;
> +
>  	tracecmd_msg_init(MSG_SEND_DATA, &msg);
>  
>  	msg.buf = malloc(MSG_MAX_DATA_LEN);

Nice catch. Definitely a latent bug waiting for someone to step on it.

Reviewed-by: Slavomir Kaslev <kaslevs@vmware.com>

-- Slavi