[3.19.y-ckt stable] Patch "SCSI: Fix NULL pointer dereference in runtime PM" has been added to staging queue

Kamal Mostafa kamal at canonical.com
Mon Sep 21 22:26:30 UTC 2015


This is a note to let you know that I have just added a patch titled

    SCSI: Fix NULL pointer dereference in runtime PM

to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue

This patch is scheduled to be released in version 3.19.8-ckt7.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.19.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 82abd4c49d84c4687cb237d2cbcb3c07b90f147d Mon Sep 17 00:00:00 2001
From: Alan Stern <stern at rowland.harvard.edu>
Date: Mon, 17 Aug 2015 11:02:42 -0400
Subject: SCSI: Fix NULL pointer dereference in runtime PM
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

commit 49718f0fb8c9af192b33d8af3a2826db04025371 upstream.

The routines in scsi_rpm.c assume that if a runtime-PM callback is
invoked for a SCSI device, it can only mean that the device's driver
has asked the block layer to handle the runtime power management (by
calling blk_pm_runtime_init(), which among other things sets q->dev).

However, this assumption turns out to be wrong for things like the ses
driver.  Normally ses devices are not allowed to do runtime PM, but
userspace can override this setting.  If this happens, the kernel gets
a NULL pointer dereference when blk_post_runtime_resume() tries to use
the uninitialized q->dev pointer.

This patch fixes the problem by calling the block layer's runtime-PM
routines only if the device's driver really does have a runtime-PM
callback routine.  Since ses doesn't define any such callbacks, the
crash won't occur.

This fixes Bugzilla #101371.

Signed-off-by: Alan Stern <stern at rowland.harvard.edu>
Reported-by: Stanisław Pitucha <viraptor at gmail.com>
Reported-by: Ilan Cohen <ilanco at gmail.com>
Tested-by: Ilan Cohen <ilanco at gmail.com>
Reviewed-by: Johannes Thumshirn <jthumshirn at suse.de>
Signed-off-by: James Bottomley <JBottomley at Odin.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/scsi/scsi_pm.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/drivers/scsi/scsi_pm.c b/drivers/scsi/scsi_pm.c
index 9e43ae1..e4b7998 100644
--- a/drivers/scsi/scsi_pm.c
+++ b/drivers/scsi/scsi_pm.c
@@ -217,15 +217,15 @@ static int sdev_runtime_suspend(struct device *dev)
 {
 	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
 	struct scsi_device *sdev = to_scsi_device(dev);
-	int err;
+	int err = 0;

-	err = blk_pre_runtime_suspend(sdev->request_queue);
-	if (err)
-		return err;
-	if (pm && pm->runtime_suspend)
+	if (pm && pm->runtime_suspend) {
+		err = blk_pre_runtime_suspend(sdev->request_queue);
+		if (err)
+			return err;
 		err = pm->runtime_suspend(dev);
-	blk_post_runtime_suspend(sdev->request_queue, err);
-
+		blk_post_runtime_suspend(sdev->request_queue, err);
+	}
 	return err;
 }

@@ -248,11 +248,11 @@ static int sdev_runtime_resume(struct device *dev)
 	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
 	int err = 0;

-	blk_pre_runtime_resume(sdev->request_queue);
-	if (pm && pm->runtime_resume)
+	if (pm && pm->runtime_resume) {
+		blk_pre_runtime_resume(sdev->request_queue);
 		err = pm->runtime_resume(dev);
-	blk_post_runtime_resume(sdev->request_queue, err);
-
+		blk_post_runtime_resume(sdev->request_queue, err);
+	}
 	return err;
 }

--
1.9.1





More information about the kernel-team mailing list