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

[Cristian Marussi]

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@xxxxxxxxxxxxxx>
> 
> 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