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

[Hannes Reinecke]

On 1/5/21 10:45 AM, Daniel Wagner wrote:
> On Mon, Jan 04, 2021 at 06:06:10PM -0300, Enzo Matsumiya wrote:
> > @Daniel maybe try tweaking your tests to use a smaller controller
> > loss timeout (-l option)? I do this on my tests because the default
> > value kicks in about 30min after hot-removal -- i.e. you
> > have to actually wait for the timeout to expire to trigger the bug.
>
> As far I can tell, the blktests test I am using will trigger the same
> bug. The problem is that the lifetime of hwmon sysfs entry should be
> aligned to the lifetime of the nvme sysfs entry. Currently, hwmon's
> lifetime is bound to the lifetime of the ctl sysfs entry. When the nvme
> entry goes away (and obviously also the underlying device), the hwmon
> sysfs entry still references it.
Yeah, using the controller node for devm allocations is quite dodgy.
Does this one help?


diff --git a/drivers/nvme/host/hwmon.c b/drivers/nvme/host/hwmon.c
index 6fdd07fb3001..7260af028cf7 100644
--- a/drivers/nvme/host/hwmon.c
+++ b/drivers/nvme/host/hwmon.c
@@ -226,7 +226,7 @@ static const struct hwmon_chip_info

 int nvme_hwmon_init(struct nvme_ctrl *ctrl)
 {
-       struct device *dev = ctrl->dev;
+       struct device *dev = ctrl->device;
        struct nvme_hwmon_data *data;
        struct device *hwmon;
        int err;
@@ -240,8 +240,7 @@ int nvme_hwmon_init(struct nvme_ctrl *ctrl)

        err = nvme_hwmon_get_smart_log(data);
        if (err) {
-               dev_warn(ctrl->device,
-                       "Failed to read smart log (error %d)\n", err);
+               dev_warn(dev, "Failed to read smart log (error %d)\n", err);
                devm_kfree(dev, data);
                return err;
        }


Cheers,

Hannes
--
Dr. Hannes Reinecke                Kernel Storage Architect
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