Re: [PATCH 1/2] scsi: target: core: Add cmd length set before cmd complete

[Bodo Stroesser <bostroesser@xxxxxxxxx>]

On 09.02.21 08:22, Aleksandr Miloserdov wrote:
> TCM doesn't properly handle underflow case for service actions. One way to
> prevent it is to always complete command with
> target_complete_cmd_with_length, however it requires access to data_sg,
> which is not always available.
>
> This change introduces target_set_cmd_data_length function which allows to
> set command data length before completing it.
>
> Signed-off-by: Aleksandr Miloserdov <a.miloserdov@xxxxxxxxx>
> Reviewed-by: Roman Bolshakov <r.bolshakov@xxxxxxxxx>
> ---
>   drivers/target/target_core_transport.c | 15 +++++++++++----
>   include/target/target_core_backend.h   |  1 +
>   2 files changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
> index fca4bd079d02..c98540355512 100644
> --- a/drivers/target/target_core_transport.c
> +++ b/drivers/target/target_core_transport.c
> @@ -879,11 +879,9 @@ void target_complete_cmd(struct se_cmd *cmd, u8 scsi_status)
>   }
>   EXPORT_SYMBOL(target_complete_cmd);
>   
> -void target_complete_cmd_with_length(struct se_cmd *cmd, u8 scsi_status, int length)
> +void target_set_cmd_data_length(struct se_cmd *cmd, int length)
>   {
> -	if ((scsi_status == SAM_STAT_GOOD ||
> -	     cmd->se_cmd_flags & SCF_TREAT_READ_AS_NORMAL) &&
> -	    length < cmd->data_length) {
> +	if (length < cmd->data_length) {
>   		if (cmd->se_cmd_flags & SCF_UNDERFLOW_BIT) {
>   			cmd->residual_count += cmd->data_length - length;
>   		} else {
> @@ -893,6 +891,15 @@ void target_complete_cmd_with_length(struct se_cmd *cmd, u8 scsi_status, int len
>   
>   		cmd->data_length = length;
>   	}
> +}
> +EXPORT_SYMBOL(target_set_cmd_data_length);
> +
> +void target_complete_cmd_with_length(struct se_cmd *cmd, u8 scsi_status, int length)
> +{
> +	if (scsi_status == SAM_STAT_GOOD ||
> +	    cmd->se_cmd_flags & SCF_TREAT_READ_AS_NORMAL) {
> +		target_set_cmd_data_length(cmd, length);
> +	}
>   
>   	target_complete_cmd(cmd, scsi_status);
>   }
> diff --git a/include/target/target_core_backend.h b/include/target/target_core_backend.h
> index 6336780d83a7..ce2fba49c95d 100644
> --- a/include/target/target_core_backend.h
> +++ b/include/target/target_core_backend.h
> @@ -72,6 +72,7 @@ int	transport_backend_register(const struct target_backend_ops *);
>   void	target_backend_unregister(const struct target_backend_ops *);
>   
>   void	target_complete_cmd(struct se_cmd *, u8);
> +void	target_set_cmd_data_length(struct se_cmd *, int);
>   void	target_complete_cmd_with_length(struct se_cmd *, u8, int);
>   
>   void	transport_copy_sense_to_cmd(struct se_cmd *, unsigned char *);

Looks ok to me.

Reviewed-by: Bodo Stroesser <bostroesser@xxxxxxxxx>