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scsi: core: Make sure that targets outlive devices

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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: Mike Christie <michael.christie@oracle.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Bart Van Assche 2022-07-28 15:18:48 -07:00 committed by Martin K. Petersen
parent a19066788d
commit fe44260419
3 changed files with 21 additions and 3 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
drivers/scsi/scsi_scan.c
View file

@ -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);

20
drivers/scsi/scsi_sysfs.c
View file

@ -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

2
include/scsi/scsi_device.h
View file

@ -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 */