linux-kernel - [PATCH 3.10 157/268] sd: get disk reference in sd_check

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Date:   Mon, 19 Jun 2017 20:30:56 +0200
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     Hannes Reinecke <hare@...e.de>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        Jinpu Wang <jinpu.wang@...fitbricks.com>,
        Jiri Slaby <jslaby@...e.cz>, Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 157/268] sd: get disk reference in sd_check_events()

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: Jiri Slaby <jslaby@...e.cz>
Signed-off-by: Willy Tarreau <w@....eu>
---
 drivers/scsi/sd.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 749893e..880a300 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -1354,11 +1354,15 @@ static int media_not_present(struct scsi_disk *sdkp,
  **/
 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"));
 
 	/*
@@ -1415,6 +1419,7 @@ out:
 	kfree(sshdr);
 	retval = sdp->changed ? DISK_EVENT_MEDIA_CHANGE : 0;
 	sdp->changed = 0;
+	scsi_disk_put(sdkp);
 	return retval;
 }
 
-- 
2.8.0.rc2.1.gbe9624a