[PATCH] nvme: hwmon: fix crash on device teardown

[Enzo Matsumiya <ematsumiya@suse.de>]

Fix a possible NULL pointer dereference when trying to read
hwmon sysfs entries associated to NVMe-oF devices that were
hot-removed or disconnected.

Unregister the NVMe hwmon device upon controller teardown
(nvme_stop_ctrl()).

Signed-off-by: Enzo Matsumiya <ematsumiya@suse.de>
---
 drivers/nvme/host/core.c  | 1 +
 drivers/nvme/host/hwmon.c | 8 ++++++++
 drivers/nvme/host/nvme.h  | 2 ++
 3 files changed, 11 insertions(+)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 9a270e49df17..becc80a0c3b8 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -4344,6 +4344,7 @@ EXPORT_SYMBOL_GPL(nvme_complete_async_event);
 
 void nvme_stop_ctrl(struct nvme_ctrl *ctrl)
 {
+	nvme_hwmon_exit(ctrl);
 	nvme_mpath_stop(ctrl);
 	nvme_stop_keep_alive(ctrl);
 	flush_work(&ctrl->async_event_work);
diff --git a/drivers/nvme/host/hwmon.c b/drivers/nvme/host/hwmon.c
index 552dbc04567b..7f62cca4c577 100644
--- a/drivers/nvme/host/hwmon.c
+++ b/drivers/nvme/host/hwmon.c
@@ -71,6 +71,9 @@ static int nvme_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
 	int temp;
 	int err;
 
+	if (data->ctrl->state != NVME_CTRL_LIVE)
+		return -EAGAIN;
+
 	/*
 	 * First handle attributes which don't require us to read
 	 * the smart log.
@@ -253,3 +256,8 @@ int nvme_hwmon_init(struct nvme_ctrl *ctrl)
 
 	return 0;
 }
+
+void nvme_hwmon_exit(struct nvme_ctrl *ctrl)
+{
+	hwmon_device_unregister(ctrl->dev);
+}
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 567f7ad18a91..621e9b1575f6 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -807,11 +807,13 @@ static inline struct nvme_ns *nvme_get_ns_from_dev(struct device *dev)
 
 #ifdef CONFIG_NVME_HWMON
 int nvme_hwmon_init(struct nvme_ctrl *ctrl);
+void nvme_hwmon_exit(struct nvme_ctrl *ctrl);
 #else
 static inline int nvme_hwmon_init(struct nvme_ctrl *ctrl)
 {
 	return 0;
 }
+static inline void nvme_hwmon_exit(struct nvme_ctrl *ctrl) { }
 #endif
 
 u32 nvme_command_effects(struct nvme_ctrl *ctrl, struct nvme_ns *ns,
-- 
2.29.2