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

Rishabh Bhatnagar
2021-08-04T21:20:18Z

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 <rishabhb@codeaurora.org>
---
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);
}

static ssize_t protocol_version_show(struct device *dev,
--
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