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

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Message-Id: <1628029342-3638-1-git-send-email-rishabhb@codeaurora.org>
Date:   Tue,  3 Aug 2021 15:22:22 -0700
From:   Rishabh Bhatnagar <rishabhb@...eaurora.org>
To:     sudeep.holla@....com, cristian.marussi@....com
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        avajid@...eaurora.org, adharmap@...eaurora.org,
        Rishabh Bhatnagar <rishabhb@...eaurora.org>
Subject: [PATCH] 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.

Change-Id: I1214ec2c4c92c4a3ca5fa73de11e0e403b13b46a
Signed-off-by: Rishabh Bhatnagar <rishabhb@...eaurora.org>
---
 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;
 }

 void scmi_free_channel(struct scmi_chan_info *cinfo, struct idr *idr, int id)
-- 
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