Re: [PATCH next] firmware: thead,th1520-aon: Fix use after free in th1520_aon_init()

From: Markus Elfring <Markus.Elfring@web.de>
To: Dan Carpenter <dan.carpenter@linaro.org>,
	linux-riscv@lists.infradead.org
Cc: kernel-janitors@vger.kernel.org,
	LKML <linux-kernel@vger.kernel.org>, Drew Fustini <drew@pdp7.com>,
	Fu Wei <wefu@redhat.com>, Guo Ren <guoren@kernel.org>,
	Michal Wilczynski <m.wilczynski@samsung.com>,
	Ulf Hansson <ulf.hansson@linaro.org>
Subject: Re: [PATCH next] firmware: thead,th1520-aon: Fix use after free in th1520_aon_init()
Date: Sun, 16 Mar 2025 13:05:08 +0100	[thread overview]
Message-ID: <d90c0678-d2ed-4e77-901a-fdbab7dfca71@web.de> (raw)
In-Reply-To: <f19be994-d355-48a6-ab45-d0f7e5955daf@stanley.mountain>

> Record the error code before freeing "aon_chan" to avoid a
> use after free.

Would it become helpful to mention which selection of source code
analysis tools detected such a questionable implementation detail?

…
> +++ b/drivers/firmware/thead,th1520-aon.c
> @@ -203,6 +203,7 @@ struct th1520_aon_chan *th1520_aon_init(struct device *dev)
>  {
>  	struct th1520_aon_chan *aon_chan;
>  	struct mbox_client *cl;
> +	int ret;
>
>  	aon_chan = kzalloc(sizeof(*aon_chan), GFP_KERNEL);
>  	if (!aon_chan)
> @@ -217,8 +218,9 @@ struct th1520_aon_chan *th1520_aon_init(struct device *dev)
>  	aon_chan->ch = mbox_request_channel_byname(cl, "aon");
>  	if (IS_ERR(aon_chan->ch)) {
>  		dev_err(dev, "Failed to request aon mbox chan\n");
> +		ret = PTR_ERR(aon_chan->ch);
>  		kfree(aon_chan);
> -		return ERR_CAST(aon_chan->ch);
> +		return ERR_PTR(ret);
>  	}
>
>  	mutex_init(&aon_chan->transaction_lock);

May the additional variable (for an information) be defined only for
the affected if branch?
Would a smaller scope be more appropriate here?

Regards,
Markus