From fe442604199ed3e60d5411137159f9623534e956 Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Thu, 28 Jul 2022 15:18:48 -0700 Subject: 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 Cc: Mike Christie Cc: Hannes Reinecke Cc: John Garry Cc: Li Zhijian Reported-by: Mike Christie Reviewed-by: Ming Lei Reviewed-by: Mike Christie Signed-off-by: Bart Van Assche Signed-off-by: Martin K. Petersen --- drivers/scsi/scsi_scan.c | 2 ++ drivers/scsi/scsi_sysfs.c | 20 +++++++++++++++++--- include/scsi/scsi_device.h | 2 ++ 3 files changed, 21 insertions(+), 3 deletions(-) diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c index 91ac901a6682..4c1efd6a3b0c 100644 --- a/drivers/scsi/scsi_scan.c +++ b/drivers/scsi/scsi_scan.c @@ -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); diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c index 43949798a2e4..1bc9c26fe1d4 100644 --- a/drivers/scsi/scsi_sysfs.c +++ b/drivers/scsi/scsi_sysfs.c @@ -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 diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h index 7cf5f3b7589f..190d2081f4c6 100644 --- a/include/scsi/scsi_device.h +++ b/include/scsi/scsi_device.h @@ -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 */ -- cgit v1.2.3-59-g8ed1b