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

[Sagi Grimberg <sagig@dev.mellanox.co.il>]

> 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@mellanox.com>

Thanks Nic.