scsi: core: Fix a use-after-free

There are two .exit_cmd_priv implementations. Both implementations use
resources associated with the SCSI host. Make sure that these resources are
still available when .exit_cmd_priv is called by waiting inside
scsi_remove_host() until the tag set has been freed.

This commit fixes the following use-after-free:

==================================================================
BUG: KASAN: use-after-free in srp_exit_cmd_priv+0x27/0xd0 [ib_srp]
Read of size 8 at addr ffff888100337000 by task multipathd/16727
Call Trace:
 <TASK>
 dump_stack_lvl+0x34/0x44
 print_report.cold+0x5e/0x5db
 kasan_report+0xab/0x120
 srp_exit_cmd_priv+0x27/0xd0 [ib_srp]
 scsi_mq_exit_request+0x4d/0x70
 blk_mq_free_rqs+0x143/0x410
 __blk_mq_free_map_and_rqs+0x6e/0x100
 blk_mq_free_tag_set+0x2b/0x160
 scsi_host_dev_release+0xf3/0x1a0
 device_release+0x54/0xe0
 kobject_put+0xa5/0x120
 device_release+0x54/0xe0
 kobject_put+0xa5/0x120
 scsi_device_dev_release_usercontext+0x4c1/0x4e0
 execute_in_process_context+0x23/0x90
 device_release+0x54/0xe0
 kobject_put+0xa5/0x120
 scsi_disk_release+0x3f/0x50
 device_release+0x54/0xe0
 kobject_put+0xa5/0x120
 disk_release+0x17f/0x1b0
 device_release+0x54/0xe0
 kobject_put+0xa5/0x120
 dm_put_table_device+0xa3/0x160 [dm_mod]
 dm_put_device+0xd0/0x140 [dm_mod]
 free_priority_group+0xd8/0x110 [dm_multipath]
 free_multipath+0x94/0xe0 [dm_multipath]
 dm_table_destroy+0xa2/0x1e0 [dm_mod]
 __dm_destroy+0x196/0x350 [dm_mod]
 dev_remove+0x10c/0x160 [dm_mod]
 ctl_ioctl+0x2c2/0x590 [dm_mod]
 dm_ctl_ioctl+0x5/0x10 [dm_mod]
 __x64_sys_ioctl+0xb4/0xf0
 dm_ctl_ioctl+0x5/0x10 [dm_mod]
 __x64_sys_ioctl+0xb4/0xf0
 do_syscall_64+0x3b/0x90
 entry_SYSCALL_64_after_hwframe+0x46/0xb0

Link: https://lore.kernel.org/r/20220826002635.919423-1-bvanassche@acm.org
Fixes: 65ca846a5314 ("scsi: core: Introduce {init,exit}_cmd_priv()")
Cc: Ming Lei <ming.lei@redhat.com>
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: Li Zhijian <lizhijian@fujitsu.com>
Tested-by: Li Zhijian <lizhijian@fujitsu.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index 26bf3b1535959f177075961601a36f77191b61a1..9857dba09c951a68cfd94965191fb7dd30972d70 100644 (file)
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -182,6 +182,15 @@ void scsi_remove_host(struct Scsi_Host *shost)
        mutex_unlock(&shost->scan_mutex);
        scsi_proc_host_rm(shost);
 
+       /*
+        * New SCSI devices cannot be attached anymore because of the SCSI host
+        * state so drop the tag set refcnt. Wait until the tag set refcnt drops
+        * to zero because .exit_cmd_priv implementations may need the host
+        * pointer.
+        */
+       kref_put(&shost->tagset_refcnt, scsi_mq_free_tags);
+       wait_for_completion(&shost->tagset_freed);
+
        spin_lock_irqsave(shost->host_lock, flags);
        if (scsi_host_set_state(shost, SHOST_DEL))
                BUG_ON(scsi_host_set_state(shost, SHOST_DEL_RECOVERY));
@@ -245,6 +254,9 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
        if (error)
                goto fail;
 
+       kref_init(&shost->tagset_refcnt);
+       init_completion(&shost->tagset_freed);
+
        /*
         * Increase usage count temporarily here so that calling
         * scsi_autopm_put_host() will trigger runtime idle if there is
@@ -317,6 +329,7 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
        pm_runtime_disable(&shost->shost_gendev);
        pm_runtime_set_suspended(&shost->shost_gendev);
        pm_runtime_put_noidle(&shost->shost_gendev);
+       kref_put(&shost->tagset_refcnt, scsi_mq_free_tags);
  fail:
        return error;
 }
@@ -350,9 +363,6 @@ static void scsi_host_dev_release(struct device *dev)
                kfree(dev_name(&shost->shost_dev));
        }
 
-       if (shost->tag_set.tags)
-               scsi_mq_destroy_tags(shost);
-
        kfree(shost->shost_data);
 
        ida_free(&host_index_ida, shost->host_no);

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index ef08029a00793e5ba12c67551296781ec8e42c03..96e7e3eaca29d2cddf11e3133d1239d1240f5020 100644 (file)
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1983,9 +1983,13 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost)
        return blk_mq_alloc_tag_set(tag_set);
 }
 
-void scsi_mq_destroy_tags(struct Scsi_Host *shost)
+void scsi_mq_free_tags(struct kref *kref)
 {
+       struct Scsi_Host *shost = container_of(kref, typeof(*shost),
+                                              tagset_refcnt);
+
        blk_mq_free_tag_set(&shost->tag_set);
+       complete(&shost->tagset_freed);
 }
 
 /**

diff --git a/drivers/scsi/scsi_priv.h b/drivers/scsi/scsi_priv.h
index 429663bd78ecf74fc3c160d85e2ba8144d21fb01..f385b3f04d6ece02491ee606dd41aa18e03df04a 100644 (file)
--- a/drivers/scsi/scsi_priv.h
+++ b/drivers/scsi/scsi_priv.h
@@ -94,7 +94,7 @@ extern void scsi_run_host_queues(struct Scsi_Host *shost);
 extern void scsi_requeue_run_queue(struct work_struct *work);
 extern void scsi_start_queue(struct scsi_device *sdev);
 extern int scsi_mq_setup_tags(struct Scsi_Host *shost);
-extern void scsi_mq_destroy_tags(struct Scsi_Host *shost);
+extern void scsi_mq_free_tags(struct kref *kref);
 extern void scsi_exit_queue(void);
 extern void scsi_evt_thread(struct work_struct *work);
 

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 91ac901a66826ef28fc8e9fded30f98a393e5bf2..5d27f5196de6fd49537ba29d9d3814207380e0ea 100644 (file)
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -340,6 +340,7 @@ static struct scsi_device *scsi_alloc_sdev(struct scsi_target *starget,
                kfree(sdev);
                goto out;
        }
+       kref_get(&sdev->host->tagset_refcnt);
        sdev->request_queue = q;
        q->queuedata = sdev;
        __scsi_init_queue(sdev->host, q);

diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index aa70d9282161d5be2412531ecacab68c0c82ebcc..5d61f58399dca4d63bf733419258da4ac739cc80 100644 (file)
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -1476,6 +1476,7 @@ void __scsi_remove_device(struct scsi_device *sdev)
        mutex_unlock(&sdev->state_mutex);
 
        blk_mq_destroy_queue(sdev->request_queue);
+       kref_put(&sdev->host->tagset_refcnt, scsi_mq_free_tags);
        cancel_work_sync(&sdev->requeue_work);
 
        if (sdev->host->hostt->slave_destroy)

diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index b6e41ee3d566ecd29b9f0295eb85efaaafb0cc8e..9b0a028bf053af2e165ed255122343b4b16f527b 100644 (file)
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -557,6 +557,8 @@ struct Scsi_Host {
        struct scsi_host_template *hostt;
        struct scsi_transport_template *transportt;
 
+       struct kref             tagset_refcnt;
+       struct completion       tagset_freed;
        /* Area to keep a shared tag map */
        struct blk_mq_tag_set   tag_set;