Re: [PATCH] rtla/osnoise: prevent NULL dereference in error handling

[John Kacur <jkacur@redhat.com>]

On Fri, 9 Aug 2024, Steven Rostedt wrote:

> On Fri, 9 Aug 2024 13:34:28 -0400 (EDT)
> John Kacur <jkacur@redhat.com> wrote:
> 
> > On Fri, 9 Aug 2024, Dan Carpenter wrote:
> > 
> > > If the "tool->data" allocation fails then there is no need to call
> > > osnoise_free_top() and, in fact, doing so will lead to a NULL dereference.
> > > 
> > > Fixes: 1eceb2fc2ca5 ("rtla/osnoise: Add osnoise top mode")
> > > Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
> > > ---
> > >  tools/tracing/rtla/src/osnoise_top.c | 11 ++++-------
> > >  1 file changed, 4 insertions(+), 7 deletions(-)
> > > 
> > > diff --git a/tools/tracing/rtla/src/osnoise_top.c b/tools/tracing/rtla/src/osnoise_top.c
> > > index f594a44df840..2f756628613d 100644
> > > --- a/tools/tracing/rtla/src/osnoise_top.c
> > > +++ b/tools/tracing/rtla/src/osnoise_top.c
> > > @@ -651,8 +651,10 @@ struct osnoise_tool *osnoise_init_top(struct osnoise_top_params *params)
> > >  		return NULL;
> > >  
> > >  	tool->data = osnoise_alloc_top(nr_cpus);
> > > -	if (!tool->data)
> > > -		goto out_err;
> > > +	if (!tool->data) {
> > > +		osnoise_destroy_tool(tool);
> > > +		return NULL;
> > > +	}
> > >  
> > >  	tool->params = params;
> > >  
> > > @@ -660,11 +662,6 @@ struct osnoise_tool *osnoise_init_top(struct osnoise_top_params *params)
> > >  				   osnoise_top_handler, NULL);
> > >  
> > >  	return tool;
> > > -
> > > -out_err:
> > > -	osnoise_free_top(tool->data);
> > > -	osnoise_destroy_tool(tool);
> > > -	return NULL;
> > >  }
> > >  
> > >  static int stop_tracing;
> > > --   
> > 
> > Although your fix appears to be correct, I wonder if it would be better to 
> > create a second error label, such as out_destroy_tool: as described in 
> > section 7 of the coding-style.rst
> > 
> 
> There's no reason for that. It's the only error path. That is, nothing
> would jump to the original out_err:
> 
> And for a single error, an if statement is good enough.
> 
> -- Steve
> 
> 

Ah, right of course.
Okay in that case, Signed-off-by: John Kacur <jkacur@redhat.com>
(applied the patch, built and ran)