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

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

[Steven Rostedt]

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);
-- 
2.20.1

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

[Slavomir Kaslev]

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

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

[Steven Rostedt]

On Fri, 22 Mar 2019 11:49:29 +0000
Slavomir Kaslev <kaslevs@vmware.com> wrote:

> > 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>

Yeah, it tripped me up, as I had a box that crashed because of it.
Delaying the finishing of the testing. Which I'm rerunning now.

-- Steve