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 --- include/scsi/scsi_device.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/scsi') 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 From 16728aaba62e8b3b170735fdc3d8aa972835c136 Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Thu, 28 Jul 2022 15:18:49 -0700 Subject: scsi: core: Make sure that hosts outlive targets Fix the race conditions between SCSI LLD kernel module unloading and SCSI device and target removal by making sure that SCSI hosts are destroyed after all associated target and device objects have been freed. Link: https://lore.kernel.org/r/20220728221851.1822295-3-bvanassche@acm.org Cc: Christoph Hellwig Cc: Ming Lei Cc: Mike Christie Cc: Hannes Reinecke Cc: John Garry Reviewed-by: Mike Christie Signed-off-by: Ming Lei Signed-off-by: Bart Van Assche [ bvanassche: Reworked Ming's patch and split it ] Signed-off-by: Martin K. Petersen --- drivers/scsi/hosts.c | 8 ++++++++ drivers/scsi/scsi_scan.c | 7 +++++++ include/scsi/scsi_host.h | 3 +++ 3 files changed, 18 insertions(+) (limited to 'include/scsi') diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c index ef6c0e37acce..8fa98c8d0ee0 100644 --- a/drivers/scsi/hosts.c +++ b/drivers/scsi/hosts.c @@ -190,6 +190,13 @@ void scsi_remove_host(struct Scsi_Host *shost) transport_unregister_device(&shost->shost_gendev); device_unregister(&shost->shost_dev); device_del(&shost->shost_gendev); + + /* + * After scsi_remove_host() has returned the scsi LLD module can be + * unloaded and/or the host resources can be released. Hence wait until + * the dependent SCSI targets and devices are gone before returning. + */ + wait_event(shost->targets_wq, atomic_read(&shost->target_count) == 0); } EXPORT_SYMBOL(scsi_remove_host); @@ -394,6 +401,7 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize) INIT_LIST_HEAD(&shost->starved_list); init_waitqueue_head(&shost->host_wait); mutex_init(&shost->scan_mutex); + init_waitqueue_head(&shost->targets_wq); index = ida_alloc(&host_index_ida, GFP_KERNEL); if (index < 0) { diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c index 4c1efd6a3b0c..ac6059702d13 100644 --- a/drivers/scsi/scsi_scan.c +++ b/drivers/scsi/scsi_scan.c @@ -406,9 +406,14 @@ static void scsi_target_destroy(struct scsi_target *starget) static void scsi_target_dev_release(struct device *dev) { struct device *parent = dev->parent; + struct Scsi_Host *shost = dev_to_shost(parent); struct scsi_target *starget = to_scsi_target(dev); kfree(starget); + + if (atomic_dec_return(&shost->target_count) == 0) + wake_up(&shost->targets_wq); + put_device(parent); } @@ -523,6 +528,8 @@ static struct scsi_target *scsi_alloc_target(struct device *parent, starget->max_target_blocked = SCSI_DEFAULT_TARGET_BLOCKED; init_waitqueue_head(&starget->sdev_wq); + atomic_inc(&shost->target_count); + retry: spin_lock_irqsave(shost->host_lock, flags); diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h index 667d889b92b5..339f975d356e 100644 --- a/include/scsi/scsi_host.h +++ b/include/scsi/scsi_host.h @@ -689,6 +689,9 @@ struct Scsi_Host { /* ldm bits */ struct device shost_gendev, shost_dev; + atomic_t target_count; + wait_queue_head_t targets_wq; + /* * Points to the transport data (if any) which is allocated * separately -- cgit v1.2.3