linux-kernel - [PATCH] scsi: storvsc: Fix a panic in the hibernation procedure

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Message-Id: <1587514644-47058-1-git-send-email-decui@microsoft.com>
Date:   Tue, 21 Apr 2020 17:17:24 -0700
From:   Dexuan Cui <decui@...rosoft.com>
To:     jejb@...ux.ibm.com, martin.petersen@...cle.com,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        hch@....de, bvanassche@....org, hare@...e.de,
        mikelley@...rosoft.com, longli@...rosoft.com, ming.lei@...hat.com
Cc:     linux-hyperv@...r.kernel.org, wei.liu@...nel.org,
        sthemmin@...rosoft.com, haiyangz@...rosoft.com, kys@...rosoft.com,
        Dexuan Cui <decui@...rosoft.com>
Subject: [PATCH] scsi: storvsc: Fix a panic in the hibernation procedure

During hibernation, the sdevs are suspended automatically in
drivers/scsi/scsi_pm.c before storvsc_suspend(), so after
storvsc_suspend(), there is no disk I/O from the file systems, but there
can still be disk I/O from the kernel space, e.g. disk_check_events() ->
sr_block_check_events() -> cdrom_check_events() can still submit I/O
to the storvsc driver, which causes a paic of NULL pointer dereference,
since storvsc has closed the vmbus channel in storvsc_suspend(): refer
to the below links for more info:
  https://lkml.org/lkml/2020/4/10/47
  https://lkml.org/lkml/2020/4/17/1103

Fix the panic by blocking/unblocking all the I/O queues properly.

Note: this patch depends on another patch "scsi: core: Allow the state
change from SDEV_QUIESCE to SDEV_BLOCK" (refer to the second link above).

Fixes: 56fb10585934 ("scsi: storvsc: Add the support of hibernation")
Signed-off-by: Dexuan Cui <decui@...rosoft.com>
---
 drivers/scsi/storvsc_drv.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
index fb41636519ee..fd51d2f03778 100644
--- a/drivers/scsi/storvsc_drv.c
+++ b/drivers/scsi/storvsc_drv.c
@@ -1948,6 +1948,11 @@ static int storvsc_suspend(struct hv_device *hv_dev)
 	struct storvsc_device *stor_device = hv_get_drvdata(hv_dev);
 	struct Scsi_Host *host = stor_device->host;
 	struct hv_host_device *host_dev = shost_priv(host);
+	int ret;
+
+	ret = scsi_host_block(host);
+	if (ret)
+		return ret;

 	storvsc_wait_to_drain(stor_device);

@@ -1968,10 +1973,15 @@ static int storvsc_suspend(struct hv_device *hv_dev)

 static int storvsc_resume(struct hv_device *hv_dev)
 {
+	struct storvsc_device *stor_device = hv_get_drvdata(hv_dev);
+	struct Scsi_Host *host = stor_device->host;
 	int ret;

 	ret = storvsc_connect_to_vsp(hv_dev, storvsc_ringbuffer_size,
 				     hv_dev_is_fc(hv_dev));
+	if (!ret)
+		ret = scsi_host_unblock(host, SDEV_RUNNING);
+
 	return ret;
 }

-- 
2.19.1