Re: [PATCH] bus: fsl-mc: fix double-free on mc_dev

[Greg KH]

On Wed, Nov 08, 2023 at 06:45:46PM +0200, Ioana Ciornei wrote:
> The blamed commit tried to simplify how the deallocations are done but,
> in the process, introduced a double-free on the mc_dev variable.
> 
> In case the MC device is a DPRC, a new mc_bus is allocated and the
> mc_dev variable is just a reference to one of its fields. In this
> circumstance, on the error path only the mc_bus should be freed.
> 
> This commit introduces back the following checkpatch warning which is a
> false-positive.
> 
> WARNING: kfree(NULL) is safe and this check is probably not required
> +       if (mc_bus)
> +               kfree(mc_bus);
> 
> Fixes: a042fbed0290 ("staging: fsl-mc: simplify couple of deallocations")
> Signed-off-by: Ioana Ciornei <ioana.ciornei@xxxxxxx>
> ---
>  drivers/bus/fsl-mc/fsl-mc-bus.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/bus/fsl-mc/fsl-mc-bus.c b/drivers/bus/fsl-mc/fsl-mc-bus.c
> index 2f6d5002e43d..b405ee330af1 100644
> --- a/drivers/bus/fsl-mc/fsl-mc-bus.c
> +++ b/drivers/bus/fsl-mc/fsl-mc-bus.c
> @@ -905,8 +905,10 @@ int fsl_mc_device_add(struct fsl_mc_obj_desc *obj_desc,
>  
>  error_cleanup_dev:
>  	kfree(mc_dev->regions);
> -	kfree(mc_bus);
> -	kfree(mc_dev);
> +	if (mc_bus)
> +		kfree(mc_bus);
> +	else
> +		kfree(mc_dev);
>  
>  	return error;
>  }
> -- 
> 2.25.1
> 

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
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created.  Hopefully you will not take offence and will fix the problem
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thanks,

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