[PATCH 04/33] target: Fix BYTCHK=0 handling for VERIFY and WRITE AND VERIFY commands

[Bart Van Assche <bart.vanassche@xxxxxxxxxxx>]

For VERIFY and WRITE AND VERIFY commands the size of the SCSI
Data-Out buffer can differ from the size of the data area on the
storage medium that is affected by the command. Make sure that
the Data-Out buffer size is computed correctly if the BYTCHK
field in the CDB is zero. This patch reverts commit 984a9d4c40be
and thereby restores commit 0e2eb7d12eaa. Additionally,
sbc_parse_cdb() is modified such that the data buffer size is
computed correctly for the affected commands if BYTCHK == 0.
This patch is the combination of two patches that got positive
reviews.

References: commit 984a9d4c40be ("Revert "target: Fix VERIFY and WRITE VERIFY command parsing"")
References: commit 0e2eb7d12eaa ("target: Fix VERIFY and WRITE VERIFY command parsing")
Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Andy Grover <agrover@xxxxxxxxxx>
Cc: David Disseldorp <ddiss@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
---
 drivers/target/target_core_sbc.c | 79 ++++++++++++++++++++++++++++++++++------
 1 file changed, 67 insertions(+), 12 deletions(-)

diff --git a/drivers/target/target_core_sbc.c b/drivers/target/target_core_sbc.c
index 4316f7b65fb7..51489d96cb31 100644
--- a/drivers/target/target_core_sbc.c
+++ b/drivers/target/target_core_sbc.c
@@ -831,12 +831,67 @@ sbc_check_dpofua(struct se_device *dev, struct se_cmd *cmd, unsigned char *cdb)
 	return 0;
 }
 
+/**
+ * sbc_parse_verify - parse VERIFY, VERIFY_16 and WRITE VERIFY commands
+ * @cmd:     (in)  structure that describes the SCSI command to be parsed.
+ * @sectors: (out) Number of logical blocks on the storage medium that will be
+ *           affected by the SCSI command.
+ * @bufflen: (out) Expected length of the SCSI Data-Out buffer.
+ */
+static sense_reason_t sbc_parse_verify(struct se_cmd *cmd, int *sectors,
+				       u32 *bufflen)
+{
+	struct se_device *dev = cmd->se_dev;
+	u8 *cdb = cmd->t_task_cdb;
+	u8 bytchk = (cdb[1] >> 1) & 3;
+	sense_reason_t ret;
+
+	switch (cdb[0]) {
+	case VERIFY:
+	case WRITE_VERIFY:
+		*sectors = transport_get_sectors_10(cdb);
+		cmd->t_task_lba = transport_lba_32(cdb);
+		break;
+	case VERIFY_16:
+	case WRITE_VERIFY_16:
+		*sectors = transport_get_sectors_16(cdb);
+		cmd->t_task_lba = transport_lba_64(cdb);
+		break;
+	default:
+		WARN_ON_ONCE(true);
+		return TCM_UNSUPPORTED_SCSI_OPCODE;
+	}
+
+	if (sbc_check_dpofua(dev, cmd, cdb))
+		return TCM_INVALID_CDB_FIELD;
+
+	ret = sbc_check_prot(dev, cmd, cdb, *sectors, true);
+	if (ret)
+		return ret;
+
+	switch (bytchk) {
+	case 0:
+		*bufflen = 0;
+		break;
+	case 1:
+		*bufflen = sbc_get_size(cmd, *sectors);
+		cmd->se_cmd_flags |= SCF_SCSI_DATA_CDB;
+		break;
+	default:
+		pr_err("Unsupported BYTCHK value %d for SCSI opcode %#x\n",
+		       bytchk, cdb[0]);
+		return TCM_INVALID_CDB_FIELD;
+	}
+	return TCM_NO_SENSE;
+}
+
 sense_reason_t
 sbc_parse_cdb(struct se_cmd *cmd, struct sbc_ops *ops)
 {
+	enum { INVALID_SIZE = 1 };
 	struct se_device *dev = cmd->se_dev;
 	unsigned char *cdb = cmd->t_task_cdb;
-	unsigned int size;
+	unsigned int size = INVALID_SIZE;
 	u32 sectors = 0;
 	sense_reason_t ret;
 
@@ -898,7 +953,6 @@ sbc_parse_cdb(struct se_cmd *cmd, struct sbc_ops *ops)
 		cmd->execute_cmd = sbc_execute_rw;
 		break;
 	case WRITE_10:
-	case WRITE_VERIFY:
 		sectors = transport_get_sectors_10(cdb);
 		cmd->t_task_lba = transport_lba_32(cdb);
 
@@ -912,6 +966,13 @@ sbc_parse_cdb(struct se_cmd *cmd, struct sbc_ops *ops)
 		cmd->se_cmd_flags |= SCF_SCSI_DATA_CDB;
 		cmd->execute_cmd = sbc_execute_rw;
 		break;
+	case WRITE_VERIFY:
+	case WRITE_VERIFY_16:
+		ret = sbc_parse_verify(cmd, &sectors, &size);
+		if (ret)
+			return ret;
+		cmd->execute_cmd = sbc_execute_rw;
+		goto check_lba;
 	case WRITE_12:
 		sectors = transport_get_sectors_12(cdb);
 		cmd->t_task_lba = transport_lba_32(cdb);
@@ -927,7 +988,6 @@ sbc_parse_cdb(struct se_cmd *cmd, struct sbc_ops *ops)
 		cmd->execute_cmd = sbc_execute_rw;
 		break;
 	case WRITE_16:
-	case WRITE_VERIFY_16:
 		sectors = transport_get_sectors_16(cdb);
 		cmd->t_task_lba = transport_lba_64(cdb);
 
@@ -1110,14 +1170,9 @@ sbc_parse_cdb(struct se_cmd *cmd, struct sbc_ops *ops)
 		break;
 	case VERIFY:
 	case VERIFY_16:
-		size = 0;
-		if (cdb[0] == VERIFY) {
-			sectors = transport_get_sectors_10(cdb);
-			cmd->t_task_lba = transport_lba_32(cdb);
-		} else {
-			sectors = transport_get_sectors_16(cdb);
-			cmd->t_task_lba = transport_lba_64(cdb);
-		}
+		ret = sbc_parse_verify(cmd, &sectors, &size);
+		if (ret)
+			return ret;
 		cmd->execute_cmd = sbc_emulate_noop;
 		goto check_lba;
 	case REZERO_UNIT:
@@ -1158,7 +1213,7 @@ sbc_parse_cdb(struct se_cmd *cmd, struct sbc_ops *ops)
 			return TCM_ADDRESS_OUT_OF_RANGE;
 		}
 
-		if (!(cmd->se_cmd_flags & SCF_COMPARE_AND_WRITE))
+		if (size == INVALID_SIZE)
 			size = sbc_get_size(cmd, sectors);
 	}
 
-- 
2.12.2