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

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Date:   Mon, 11 Jan 2021 17:00:18 +0100
From:   Hannes Reinecke <hare@...e.de>
To:     Daniel Wagner <dwagner@...e.de>,
        Enzo Matsumiya <ematsumiya@...e.de>
Cc:     Sagi Grimberg <sagi@...mberg.me>, linux-kernel@...r.kernel.org,
        linux-nvme@...ts.infradead.org, Jens Axboe <axboe@...com>,
        Keith Busch <kbusch@...nel.org>, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH] nvme: hwmon: fix crash on device teardown

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
hare@...e.de                              +49 911 74053 688
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