linux-kernel - Re: [PATCH] firmware: arm_scmi: Free mailbox channels if probe fails

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Message-ID: <20210804083358.GR6592@e120937-lin>
Date:   Wed, 4 Aug 2021 09:33:58 +0100
From:   Cristian Marussi <cristian.marussi@....com>
To:     Rishabh Bhatnagar <rishabhb@...eaurora.org>
Cc:     sudeep.holla@....com, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, avajid@...eaurora.org,
        adharmap@...eaurora.org
Subject: Re: [PATCH] firmware: arm_scmi: Free mailbox channels if probe fails

On Tue, Aug 03, 2021 at 03:22:22PM -0700, Rishabh Bhatnagar wrote:
> Mailbox channels for the base protocol are setup during probe.
> There can be a scenario where probe fails to acquire the base
> protocol due to a timeout leading to cleaning up of all device
> managed memory including the scmi_mailbox structure setup during
> mailbox_chan_setup function.
> [   12.735104]arm-scmi soc:qcom,scmi: timed out in resp(caller: version_get+0x84/0x140)
> [   12.735224]arm-scmi soc:qcom,scmi: unable to communicate with SCMI
> [   12.735947]arm-scmi: probe of soc:qcom,scmi failed with error -110
> 
> Now when a message arrives at cpu slightly after the timeout, the mailbox
> controller will try to call the rx_callback of the client and might end
> up accessing freed memory.
> [   12.758363][    C0] Call trace:
> [   12.758367][    C0]  rx_callback+0x24/0x160
> [   12.758372][    C0]  mbox_chan_received_data+0x44/0x94
> [   12.758386][    C0]  __handle_irq_event_percpu+0xd4/0x240
> This patch frees the mailbox channels setup during probe and adds some more
> error handling in case the probe fails.
> 
> Change-Id: I1214ec2c4c92c4a3ca5fa73de11e0e403b13b46a
> Signed-off-by: Rishabh Bhatnagar <rishabhb@...eaurora.org>

Hi Rishabh,

Good catch, thanks for this.

> ---
>  drivers/firmware/arm_scmi/driver.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
> index 9b2e8d4..518c7b9 100644
> --- a/drivers/firmware/arm_scmi/driver.c
> +++ b/drivers/firmware/arm_scmi/driver.c
> @@ -1430,7 +1430,7 @@ static int scmi_probe(struct platform_device *pdev)
>  
>  	ret = scmi_xfer_info_init(info);
>  	if (ret)
> -		return ret;
> +		goto clear_txrx_setup;
>  
>  	if (scmi_notification_init(handle))
>  		dev_err(dev, "SCMI Notifications NOT available.\n");
> @@ -1443,7 +1443,7 @@ static int scmi_probe(struct platform_device *pdev)
>  	ret = scmi_protocol_acquire(handle, SCMI_PROTOCOL_BASE);
>  	if (ret) {
>  		dev_err(dev, "unable to communicate with SCMI\n");
> -		return ret;
> +		goto notification_exit;
>  	}
>  
>  	mutex_lock(&scmi_list_mutex);
> @@ -1482,6 +1482,13 @@ static int scmi_probe(struct platform_device *pdev)
>  	}
>  
>  	return 0;
> +
> +notification_exit:
> +	scmi_notification_exit(&info->handle);
> +clear_txrx_setup:
> +	idr_for_each(&info->tx_idr, info->desc->ops->chan_free, &info->tx_idr);
> +	idr_for_each(&info->rx_idr, info->desc->ops->chan_free, &info->rx_idr);
> +	return ret;
>  }
>  

Shouldn't we also clear the internal IDRs memory allocs after these
idr_for_each() adding a couple of:

	idr_destroy(&info->tx_idr);

	idr_destroy(&info->rx_idr);

like scmi_remove() does ?

Thanks,
Cristian