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[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: Dariusz Majchrzak <dariusz.majchrzak@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
This commit is contained in:
Dan Williams 2012-06-21 23:47:28 -07:00 committed by James Bottomley
parent b5f1758f22
commit 3b661a92e8
2 changed files with 30 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
drivers/scsi/scsi_scan.c
View File

@ -1717,6 +1717,9 @@ static void scsi_sysfs_add_devices(struct Scsi_Host *shost)
{ {
struct scsi_device *sdev; struct scsi_device *sdev;
shost_for_each_device(sdev, shost) { 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) || if (!scsi_host_scan_allowed(shost) ||
scsi_sysfs_add_sdev(sdev) != 0) scsi_sysfs_add_sdev(sdev) != 0)
__scsi_remove_device(sdev); __scsi_remove_device(sdev);

43
drivers/scsi/scsi_sysfs.c
View File

@ -1005,7 +1005,6 @@ static void __scsi_remove_target(struct scsi_target *starget)
struct scsi_device *sdev; struct scsi_device *sdev;
spin_lock_irqsave(shost->host_lock, flags); spin_lock_irqsave(shost->host_lock, flags);
starget->reap_ref++;
restart: restart:
list_for_each_entry(sdev, &shost->__devices, siblings) { list_for_each_entry(sdev, &shost->__devices, siblings) {
if (sdev->channel != starget->channel || if (sdev->channel != starget->channel ||
@ -1019,14 +1018,6 @@ static void __scsi_remove_target(struct scsi_target *starget)
goto restart; goto restart;
} }
spin_unlock_irqrestore(shost->host_lock, flags); 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) void scsi_remove_target(struct device *dev)
{ {
if (scsi_is_target_device(dev)) { struct Scsi_Host *shost = dev_to_shost(dev->parent);
__scsi_remove_target(to_scsi_target(dev)); struct scsi_target *starget, *found;
return; unsigned long flags;
}
get_device(dev); restart:
device_for_each_child(dev, NULL, __remove_child); found = NULL;
put_device(dev); 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);
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); EXPORT_SYMBOL(scsi_remove_target);