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

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Message-ID: <c73c51ae-99da-793a-6dcb-2fbc6871261d@redhat.com>
Date: Fri, 9 Aug 2024 13:34:28 -0400 (EDT)
From: John Kacur <jkacur@...hat.com>
To: Dan Carpenter <dan.carpenter@...aro.org>
cc: Daniel Bristot de Oliveira <bristot@...nel.org>, 
    Steven Rostedt <rostedt@...dmis.org>, 
    "Luis Claudio R. Goncalves" <lgoncalv@...hat.com>, 
    Clark Williams <williams@...hat.com>, linux-trace-kernel@...r.kernel.org, 
    linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] rtla/osnoise: prevent NULL dereference in error
 handling



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@...aro.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

Thanks

John Kacur