linux-kernel - Re: [PATCH] rpmsg: virtio: fix possible double free in rpmsg

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Date:   Mon, 25 Apr 2022 10:55:52 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Hangyu Hua <hbh25y@...il.com>
Cc:     bjorn.andersson@...aro.org, arnaud.pouliquen@...s.st.com,
        linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rpmsg: virtio: fix possible double free in rpmsg_probe()

On Mon, Apr 18, 2022 at 05:31:44PM +0800, Hangyu Hua wrote:
> vch will be free in virtio_rpmsg_release_device() when
> rpmsg_ns_register_device() fails. There is no need to call kfree() again.
> 
> Fix this by changing error path from free_vch to free_ctrldev.
> 
> Fixes: c486682ae1e2 ("rpmsg: virtio: Register the rpmsg_char device")
> Signed-off-by: Hangyu Hua <hbh25y@...il.com>
> ---
>  drivers/rpmsg/virtio_rpmsg_bus.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c
> index 3ede25b1f2e4..603233f0686e 100644
> --- a/drivers/rpmsg/virtio_rpmsg_bus.c
> +++ b/drivers/rpmsg/virtio_rpmsg_bus.c
> @@ -973,7 +973,7 @@ static int rpmsg_probe(struct virtio_device *vdev)
>  
>  		err = rpmsg_ns_register_device(rpdev_ns);
>  		if (err)
> -			goto free_vch;

Please add a comment that highlights where 'vch' will be free'd to avoid
receiving patches that will introduce another kfree().  Same for your other
patch.

In the next revision please use a cover letter and add Arnaud's patches to it.

Thanks,
Mathieu

> +			goto free_ctrldev;
>  	}
>  
>  	/*
> @@ -997,8 +997,6 @@ static int rpmsg_probe(struct virtio_device *vdev)
>  
>  	return 0;
>  
> -free_vch:
> -	kfree(vch);
>  free_ctrldev:
>  	rpmsg_virtio_del_ctrl_dev(rpdev_ctrl);
>  free_coherent:
> -- 
> 2.25.1
>