Re: [PATCH v3] firmware: arm_scmi: Free mailbox channels if probe fails

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.

Signed-off-by: Rishabh Bhatnagar <redacted>
---
 drivers/firmware/arm_scmi/driver.c | 35 ++++++++++++++++++++++++-----------
 1 file changed, 24 insertions(+), 11 deletions(-)

diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index 9b2e8d4..ead3bd3 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c

@@ -1390,6 +1390,21 @@ void scmi_protocol_device_unrequest(const struct scmi_device_id *id_table)
 	mutex_unlock(&scmi_requested_devices_mtx);
 }
 

+static int scmi_cleanup_txrx_channels(struct scmi_info *info)
+{
+	int ret;
+	struct idr *idr = &info->tx_idr;
+
+	ret = idr_for_each(idr, info->desc->ops->chan_free, idr);
+	idr_destroy(&info->tx_idr);
+
+	idr = &info->rx_idr;
+	ret = idr_for_each(idr, info->desc->ops->chan_free, idr);
+	idr_destroy(&info->rx_idr);
+
+	return ret;
+}
+
 static int scmi_probe(struct platform_device *pdev)
 {
 	int ret;

@@ -1430,7 +1445,7 @@ 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 +1458,7 @@ 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 +1497,12 @@ static int scmi_probe(struct platform_device *pdev)
 	}
 
 	return 0;
+
+notification_exit:
+	scmi_notification_exit(&info->handle);
+clear_txrx_setup:
+	scmi_cleanup_txrx_channels(info);
+	return ret;
 }
 
 void scmi_free_channel(struct scmi_chan_info *cinfo, struct idr *idr, int id)

@@ -1493,7 +1514,6 @@ static int scmi_remove(struct platform_device *pdev)
 {
 	int ret = 0, id;
 	struct scmi_info *info = platform_get_drvdata(pdev);
-	struct idr *idr = &info->tx_idr;
 	struct device_node *child;
 
 	mutex_lock(&scmi_list_mutex);

@@ -1517,14 +1537,7 @@ static int scmi_remove(struct platform_device *pdev)
 	idr_destroy(&info->active_protocols);
 
 	/* Safe to free channels since no more users */
-	ret = idr_for_each(idr, info->desc->ops->chan_free, idr);
-	idr_destroy(&info->tx_idr);
-
-	idr = &info->rx_idr;
-	ret = idr_for_each(idr, info->desc->ops->chan_free, idr);
-	idr_destroy(&info->rx_idr);
-
-	return ret;
+	return scmi_cleanup_txrx_channels(info);
 }