linux-kernel - [PATCH 3.2 23/67] SCSI: fix crashes in sd and sr runtime PM

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Message-ID: <lsq.1456263723.891877111@decadent.org.uk>
Date:	Tue, 23 Feb 2016 21:42:03 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"James Bottomley" <James.Bottomley@...senPartnership.com>,
	"Alexandre Rossi" <alexandre.rossi@...il.com>,
	"Paul Menzel" <paul.menzel@...ntmonkey.de>,
	"Alan Stern" <stern@...land.harvard.edu>,
	"Erich Schubert" <erich@...ian.org>
Subject: [PATCH 3.2 23/67] SCSI: fix crashes in sd and sr runtime PM

3.2.78-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Alan Stern <stern@...land.harvard.edu>

commit 13b4389143413a1f18127c07f72c74cad5b563e8 upstream.

Runtime suspend during driver probe and removal can cause problems.
The driver's runtime_suspend or runtime_resume callbacks may invoked
before the driver has finished binding to the device or after the
driver has unbound from the device.

This problem shows up with the sd and sr drivers, and can cause disk
or CD/DVD drives to become unusable as a result.  The fix is simple.
The drivers store a pointer to the scsi_disk or scsi_cd structure as
their private device data when probing is finished, so we simply have
to be sure to clear the private data during removal and test it during
runtime suspend/resume.

This fixes <https://bugs.debian.org/801925>.

Signed-off-by: Alan Stern <stern@...land.harvard.edu>
Reported-by: Paul Menzel <paul.menzel@...ntmonkey.de>
Reported-by: Erich Schubert <erich@...ian.org>
Reported-by: Alexandre Rossi <alexandre.rossi@...il.com>
Tested-by: Paul Menzel <paul.menzel@...ntmonkey.de>
Tested-by: Erich Schubert <erich@...ian.org>
Signed-off-by: James Bottomley <James.Bottomley@...senPartnership.com>
[bwh: Backported to 3.2: drop changes to sr as it doesn't support runtime PM]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -2767,8 +2767,8 @@ static int sd_suspend(struct device *dev
 	struct scsi_disk *sdkp = scsi_disk_get_from_dev(dev);
 	int ret = 0;
 
-	if (!sdkp)
-		return 0;	/* this can happen */
+	if (!sdkp)	/* E.g.: runtime suspend following sd_remove() */
+		return 0;
 
 	if (sdkp->WCE) {
 		sd_printk(KERN_NOTICE, sdkp, "Synchronizing SCSI cache\n");
@@ -2792,6 +2792,9 @@ static int sd_resume(struct device *dev)
 	struct scsi_disk *sdkp = scsi_disk_get_from_dev(dev);
 	int ret = 0;
 
+	if (!sdkp)	/* E.g.: runtime resume at the start of sd_probe() */
+		return 0;
+
 	if (!sdkp->device->manage_start_stop)
 		goto done;