linux-kernel - [PATCH 4.4 39/91] sd: get disk reference in sd_check

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Date:   Fri, 10 Mar 2017 10:08:38 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hannes Reinecke <hare@...e.de>,
        "Ewan D. Milne" <emilne@...hat.com>,
        Bart Van Assche <bart.vanassche@...disk.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Jinpu Wang <jinpu.wang@...fitbricks.com>
Subject: [PATCH 4.4 39/91] sd: get disk reference in sd_check_events()

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Hannes Reinecke <hare@...e.de>

commit eb72d0bb84eee5d0dc3044fd17b75e7101dabb57 upstream.

sd_check_events() is called asynchronously, and might race
with device removal. So always take a disk reference when
processing the event to avoid the device being removed while
the event is processed.

Signed-off-by: Hannes Reinecke <hare@...e.de>
Reviewed-by: Ewan D. Milne <emilne@...hat.com>
Reviewed-by: Bart Van Assche <bart.vanassche@...disk.com>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
Cc: Jinpu Wang <jinpu.wang@...fitbricks.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/scsi/sd.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -1398,11 +1398,15 @@ static int media_not_present(struct scsi
  **/
 static unsigned int sd_check_events(struct gendisk *disk, unsigned int clearing)
 {
-	struct scsi_disk *sdkp = scsi_disk(disk);
-	struct scsi_device *sdp = sdkp->device;
+	struct scsi_disk *sdkp = scsi_disk_get(disk);
+	struct scsi_device *sdp;
 	struct scsi_sense_hdr *sshdr = NULL;
 	int retval;
 
+	if (!sdkp)
+		return 0;
+
+	sdp = sdkp->device;
 	SCSI_LOG_HLQUEUE(3, sd_printk(KERN_INFO, sdkp, "sd_check_events\n"));
 
 	/*
@@ -1459,6 +1463,7 @@ out:
 	kfree(sshdr);
 	retval = sdp->changed ? DISK_EVENT_MEDIA_CHANGE : 0;
 	sdp->changed = 0;
+	scsi_disk_put(sdkp);
 	return retval;
 }