Commit fe442604 authored by Bart Van Assche's avatar Bart Van Assche Committed by Martin K. Petersen
Browse files

scsi: core: Make sure that targets outlive devices 

This commit prevents that the following sequence triggers a kernel crash:

 - Deletion of a SCSI device is requested via sysfs. Device removal takes
   some time because blk_cleanup_queue() is waiting for the SCSI error
   handler.

 - The SCSI target associated with that SCSI device is removed.

 - scsi_remove_target() returns and its caller frees the resources
   associated with the SCSI target.

 - The error handler makes progress and invokes an LLD callback that
   dereferences the SCSI target pointer.

Link: https://lore.kernel.org/r/20220728221851.1822295-2-bvanassche@acm.org


Cc: Christoph Hellwig <hch@lst.de>
Cc: Mike Christie <michael.christie@oracle.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: John Garry <john.garry@huawei.com>
Cc: Li Zhijian <lizhijian@fujitsu.com>
Reported-by: default avatarMike Christie <michael.christie@oracle.com>
Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
Reviewed-by: default avatarMike Christie <michael.christie@oracle.com>
Signed-off-by: default avatarBart Van Assche <bvanassche@acm.org>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent a1906678

drivers/scsi/scsi_scan.c

+2 −0
Original line number Diff line number Diff line
@@ -521,6 +521,8 @@ static struct scsi_target *scsi_alloc_target(struct device *parent, 
	starget->state = STARGET_CREATED;

	starget->scsi_level = SCSI_2;

	starget->max_target_blocked = SCSI_DEFAULT_TARGET_BLOCKED;

	init_waitqueue_head(&starget->sdev_wq);



 retry:

	spin_lock_irqsave(shost->host_lock, flags);

drivers/scsi/scsi_sysfs.c

+17 −3
Original line number Diff line number Diff line
@@ -443,7 +443,9 @@ static void scsi_device_cls_release(struct device *class_dev) 


static void scsi_device_dev_release_usercontext(struct work_struct *work)

{

	struct scsi_device *sdev;

	struct scsi_device *sdev = container_of(work, struct scsi_device,

						ew.work);

	struct scsi_target *starget = sdev->sdev_target;

	struct device *parent;

	struct list_head *this, *tmp;

	struct scsi_vpd *vpd_pg80 = NULL, *vpd_pg83 = NULL;
@@ -452,8 +454,6 @@ static void scsi_device_dev_release_usercontext(struct work_struct *work) 
	unsigned long flags;

	struct module *mod;



	sdev = container_of(work, struct scsi_device, ew.work);



	mod = sdev->host->hostt->module;



	scsi_dh_release_device(sdev);
@@ -516,6 +516,9 @@ static void scsi_device_dev_release_usercontext(struct work_struct *work) 
	kfree(sdev->inquiry);

	kfree(sdev);



	if (starget && atomic_dec_return(&starget->sdev_count) == 0)

		wake_up(&starget->sdev_wq);



	if (parent)

		put_device(parent);

	module_put(mod);
@@ -1535,6 +1538,14 @@ static void __scsi_remove_target(struct scsi_target *starget) 
		goto restart;

	}

	spin_unlock_irqrestore(shost->host_lock, flags);



	/*

	 * After scsi_remove_target() returns its caller can remove resources

	 * associated with @starget, e.g. an rport or session. Wait until all

	 * devices associated with @starget have been removed to prevent that

	 * a SCSI error handling callback function triggers a use-after-free.

	 */

	wait_event(starget->sdev_wq, atomic_read(&starget->sdev_count) == 0);

}



/**
@@ -1645,6 +1656,9 @@ void scsi_sysfs_device_initialize(struct scsi_device *sdev) 
	list_add_tail(&sdev->same_target_siblings, &starget->devices);

	list_add_tail(&sdev->siblings, &shost->__devices);

	spin_unlock_irqrestore(shost->host_lock, flags);



	atomic_inc(&starget->sdev_count);



	/*

	 * device can now only be removed via __scsi_remove_device() so hold

	 * the target.  Target will be held in CREATED state until something

include/scsi/scsi_device.h

+2 −0
Original line number Diff line number Diff line
@@ -309,6 +309,8 @@ struct scsi_target { 
	struct list_head	devices;

	struct device		dev;

	struct kref		reap_ref; /* last put renders target invisible */

	atomic_t		sdev_count;

	wait_queue_head_t	sdev_wq;

	unsigned int		channel;

	unsigned int		id; /* target id ... replace

				     * scsi_device.id eventually */