Commit 3b661a92 authored by Dan Williams's avatar Dan Williams Committed by James Bottomley
Browse files

[SCSI] fix hot unplug vs async scan race 



The following crash results from cases where the end_device has been
removed before scsi_sysfs_add_sdev has had a chance to run.

 BUG: unable to handle kernel NULL pointer dereference at 0000000000000098
 IP: [<ffffffff8115e100>] sysfs_create_dir+0x32/0xb6
 ...
 Call Trace:
  [<ffffffff8125e4a8>] kobject_add_internal+0x120/0x1e3
  [<ffffffff81075149>] ? trace_hardirqs_on+0xd/0xf
  [<ffffffff8125e641>] kobject_add_varg+0x41/0x50
  [<ffffffff8125e70b>] kobject_add+0x64/0x66
  [<ffffffff8131122b>] device_add+0x12d/0x63a
  [<ffffffff814b65ea>] ? _raw_spin_unlock_irqrestore+0x47/0x56
  [<ffffffff8107de15>] ? module_refcount+0x89/0xa0
  [<ffffffff8132f348>] scsi_sysfs_add_sdev+0x4e/0x28a
  [<ffffffff8132dcbb>] do_scan_async+0x9c/0x145

...teach scsi_sysfs_add_devices() to check for deleted devices() before
trying to add them, and teach scsi_remove_target() how to remove targets
that have not been added via device_add().

Cc: <stable@vger.kernel.org>
Reported-by: default avatarDariusz Majchrzak <dariusz.majchrzak@intel.com>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
Signed-off-by: default avatarJames Bottomley <JBottomley@Parallels.com>
parent b5f1758f

drivers/scsi/scsi_scan.c

+3 −0
Original line number Diff line number Diff line
@@ -1717,6 +1717,9 @@ static void scsi_sysfs_add_devices(struct Scsi_Host *shost) 
{

	struct scsi_device *sdev;

	shost_for_each_device(sdev, shost) {

		/* target removed before the device could be added */

		if (sdev->sdev_state == SDEV_DEL)

			continue;

		if (!scsi_host_scan_allowed(shost) ||

		    scsi_sysfs_add_sdev(sdev) != 0)

			__scsi_remove_device(sdev);

drivers/scsi/scsi_sysfs.c

+26 −15
Original line number Diff line number Diff line
@@ -1005,7 +1005,6 @@ static void __scsi_remove_target(struct scsi_target *starget) 
	struct scsi_device *sdev;



	spin_lock_irqsave(shost->host_lock, flags);

	starget->reap_ref++;

 restart:

	list_for_each_entry(sdev, &shost->__devices, siblings) {

		if (sdev->channel != starget->channel ||
@@ -1019,14 +1018,6 @@ static void __scsi_remove_target(struct scsi_target *starget) 
		goto restart;

	}

	spin_unlock_irqrestore(shost->host_lock, flags);

	scsi_target_reap(starget);

}



static int __remove_child (struct device * dev, void * data)

{

	if (scsi_is_target_device(dev))

		__scsi_remove_target(to_scsi_target(dev));

	return 0;

}



/**
@@ -1039,14 +1030,34 @@ static int __remove_child (struct device * dev, void * data) 
 */

void scsi_remove_target(struct device *dev)

{

	if (scsi_is_target_device(dev)) {

		__scsi_remove_target(to_scsi_target(dev));

		return;

	struct Scsi_Host *shost = dev_to_shost(dev->parent);

	struct scsi_target *starget, *found;

	unsigned long flags;



 restart:

	found = NULL;

	spin_lock_irqsave(shost->host_lock, flags);

	list_for_each_entry(starget, &shost->__targets, siblings) {

		if (starget->state == STARGET_DEL)

			continue;

		if (starget->dev.parent == dev || &starget->dev == dev) {

			found = starget;

			found->reap_ref++;

			break;

		}

	}

	spin_unlock_irqrestore(shost->host_lock, flags);



	get_device(dev);

	device_for_each_child(dev, NULL, __remove_child);

	put_device(dev);

	if (found) {

		__scsi_remove_target(found);

		scsi_target_reap(found);

		/* in the case where @dev has multiple starget children,

		 * continue removing.

		 *

		 * FIXME: does such a case exist?

		 */

		goto restart;

	}

}

EXPORT_SYMBOL(scsi_remove_target);

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