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

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Date:   Wed, 04 Aug 2021 10:29:28 -0700
From:   rishabhb@...eaurora.org
To:     Cristian Marussi <cristian.marussi@....com>
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 2021-08-04 01:40, Cristian Marussi wrote:
> On Wed, Aug 04, 2021 at 09:33:58AM +0100, Cristian Marussi wrote:
>> 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.
>> 
> 
> Hi again,
> 
> sorry forgot one thing.
> 
>> > ---
>> >  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 ?
>> 
> 
> Maybe it could be worth at this point unifying this common
> "cleanup-all-channels"
> logic shared between scmi_probe()-error-path and scmi_remove() into its 
> own
> helper function to call from both sites.
> 
> Thanks,
> Cristian
Thanks for the review. I'll move the cleanup to a common helper 
function.
It makes sense to destroy tx/rx idrs. I didn't realize they allocate 
memory
internally.