[PATCH AUTOSEL 5.4 32/33] scsi: target: core: Add cmd length set before cmd complete

[Sasha Levin <sashal@kernel.org>]

From: Aleksandr Miloserdov <a.miloserdov@yadro.com>

[ Upstream commit 1c73e0c5e54d5f7d77f422a10b03ebe61eaed5ad ]

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.

Link: https://lore.kernel.org/r/20210209072202.41154-2-a.miloserdov@yadro.com
Reviewed-by: Roman Bolshakov <r.bolshakov@yadro.com>
Reviewed-by: Bodo Stroesser <bostroesser@gmail.com>
Signed-off-by: Aleksandr Miloserdov <a.miloserdov@yadro.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 b1f4be055f83..a16835c0bb1d 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -873,11 +873,9 @@ 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 {
@@ -887,6 +885,15 @@ 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 51b6f50eabee..0deeff9b4496 100644
--- a/include/target/target_core_backend.h
+++ b/include/target/target_core_backend.h
@@ -69,6 +69,7 @@ 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 *);
-- 
2.30.1