This fixes data corruptions arising from concurrent enabling of a target
devices. When multiple enable calls are made concurrently then it is
possible for the target device to be set up twice which results in a
kernel BUG.
Introduces a per target device mutex for serializing enable requests.

Signed-off-by: Grzegorz Uriasz <gorbak25@gmail.com>
---
  drivers/target/target_core_device.c | 17 +++++++++++++----
  include/target/target_core_base.h   |  1 +
  2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/target/target_core_device.c 
b/drivers/target/target_core_device.c
index 90f3f4926172..6d8fb962c780 100644
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -742,6 +742,7 @@ struct se_device *target_alloc_device(struct se_hba 
*hba, const char *name)

      INIT_WORK(&dev->delayed_cmd_work, target_do_delayed_work);
      mutex_init(&dev->lun_reset_mutex);
+    mutex_init(&dev->configure_mutex);

      dev->t10_wwn.t10_dev = dev;
      /*
@@ -904,10 +905,15 @@ int target_configure_device(struct se_device *dev)
      struct se_hba *hba = dev->se_hba;
      int ret, id;

+    ret = mutex_lock_interruptible(&dev->configure_mutex);
+    if (ret)
+        return ret;
+
      if (target_dev_configured(dev)) {
          pr_err("se_dev->se_dev_ptr already set for storage"
                  " object\n");
-        return -EEXIST;
+        ret = -EEXIST;
+        goto out_release_mutex;
      }

      /*
@@ -923,7 +929,7 @@ int target_configure_device(struct se_device *dev)
      mutex_unlock(&device_mutex);
      if (id < 0) {
          ret = -ENOMEM;
-        goto out;
+        goto out_release_vpd;
      }
      dev->dev_index = id;

@@ -969,7 +975,8 @@ int target_configure_device(struct se_device *dev)

      dev->dev_flags |= DF_CONFIGURED;

-    return 0;
+    ret = 0;
+    goto out_release_mutex;

  out_destroy_device:
      dev->transport->destroy_device(dev);
@@ -977,8 +984,10 @@ int target_configure_device(struct se_device *dev)
      mutex_lock(&device_mutex);
      idr_remove(&devices_idr, dev->dev_index);
      mutex_unlock(&device_mutex);
-out:
+out_release_vpd:
      se_release_vpd_for_dev(dev);
+out_release_mutex:
+    mutex_unlock(&dev->configure_mutex);
      return ret;
  }

diff --git a/include/target/target_core_base.h 
b/include/target/target_core_base.h
index 5f8e96f1516f..b3f9bd641688 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -869,6 +869,7 @@ struct se_device {
      int            queue_cnt;
      struct se_device_queue    *queues;
      struct mutex        lun_reset_mutex;
+    struct mutex        configure_mutex;
  };

  struct target_opcode_descriptor {
-- 
2.40.0