Re: [PATCH] target: Fix target_sense_desc_format NULL pointer dereference

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How about the following to fix up TCM_WRITE_PROTECT + D_SENSE..?

diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index abf2076..ba102c5 100644
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -62,22 +62,13 @@ transport_lookup_cmd_lun(struct se_cmd *se_cmd, u64 unpacked_lun)
  	struct se_session *se_sess = se_cmd->se_sess;
  	struct se_node_acl *nacl = se_sess->se_node_acl;
  	struct se_dev_entry *deve;
+	sense_reason_t ret = TCM_NO_SENSE;

  	rcu_read_lock();
  	deve = target_nacl_find_deve(nacl, unpacked_lun);
  	if (deve) {
  		atomic_long_inc(&deve->total_cmds);

-		if ((se_cmd->data_direction == DMA_TO_DEVICE) &&
-		    (deve->lun_flags & TRANSPORT_LUNFLAGS_READ_ONLY)) {
-			pr_err("TARGET_CORE[%s]: Detected WRITE_PROTECTED LUN"
-				" Access for 0x%08llx\n",
-				se_cmd->se_tfo->get_fabric_name(),
-				unpacked_lun);
-			rcu_read_unlock();
-			return TCM_WRITE_PROTECTED;
-		}
-
  		if (se_cmd->data_direction == DMA_TO_DEVICE)
  			atomic_long_add(se_cmd->data_length,
  					&deve->write_bytes);
@@ -93,6 +84,17 @@ transport_lookup_cmd_lun(struct se_cmd *se_cmd, u64 unpacked_lun)

  		percpu_ref_get(&se_lun->lun_ref);
  		se_cmd->lun_ref_active = true;
+
+		if ((se_cmd->data_direction == DMA_TO_DEVICE) &&
+		    (deve->lun_flags & TRANSPORT_LUNFLAGS_READ_ONLY)) {
+			pr_err("TARGET_CORE[%s]: Detected WRITE_PROTECTED LUN"
+				" Access for 0x%08llx\n",
+				se_cmd->se_tfo->get_fabric_name(),
+				unpacked_lun);
+			rcu_read_unlock();
+			ret = TCM_WRITE_PROTECTED;	
+			goto ref_dev;
+		}
  	}
  	rcu_read_unlock();

@@ -109,12 +111,6 @@ transport_lookup_cmd_lun(struct se_cmd *se_cmd, u64 unpacked_lun)
  				unpacked_lun);
  			return TCM_NON_EXISTENT_LUN;
  		}
-		/*
-		 * Force WRITE PROTECT for virtual LUN 0
-		 */
-		if ((se_cmd->data_direction != DMA_FROM_DEVICE) &&
-		    (se_cmd->data_direction != DMA_NONE))
-			return TCM_WRITE_PROTECTED;

  		se_lun = se_sess->se_tpg->tpg_virt_lun0;
  		se_cmd->se_lun = se_sess->se_tpg->tpg_virt_lun0;
@@ -123,6 +119,15 @@ transport_lookup_cmd_lun(struct se_cmd *se_cmd, u64 unpacked_lun)

  		percpu_ref_get(&se_lun->lun_ref);
  		se_cmd->lun_ref_active = true;
+
+		/*
+		 * Force WRITE PROTECT for virtual LUN 0
+		 */
+		if ((se_cmd->data_direction != DMA_FROM_DEVICE) &&
+		    (se_cmd->data_direction != DMA_NONE)) {
+			ret = TCM_WRITE_PROTECTED;
+			goto ref_dev;
+		}
  	}
  	/*
  	 * RCU reference protected by percpu se_lun->lun_ref taken above that
@@ -130,6 +135,7 @@ transport_lookup_cmd_lun(struct se_cmd *se_cmd, u64 unpacked_lun)
  	 * pointer can be kfree_rcu() by the final se_lun->lun_group put via
  	 * target_core_fabric_configfs.c:target_fabric_port_release
  	 */
+ref_dev:
  	se_cmd->se_dev = rcu_dereference_raw(se_lun->lun_se_dev);
  	atomic_long_inc(&se_cmd->se_dev->num_cmds);

So transport_lookup_cmd_lun() will always assign se_dev. Looks fine.

You can add when resubmitting:
Reviewed-by: Sagi Grimberg <sagig@xxxxxxxxxxxx>

Thanks Nic.
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