[PATCH v2] ata: libata-scsi: do not lose CHECK CONDITION for failed ATAPI commands

[hengyul@cs.unc.edu]

From: Hengyu Liang <hengyul@cs.unc.edu>

Since commit 2e1d2e65e773 ("ata: libata-scsi: terminate deferred commands
on time out"), atapi_qc_complete() sets SAM_STAT_CHECK_CONDITION for a
failed command only if cmd->result is zero, so that the DID_TIME_OUT or
DID_REQUEUE host byte of a terminated command is preserved.

However, cmd->result can also be non-zero for a regular failed ATAPI
command completed through libata EH: ata_eh_analyze_tf() calls
ata_eh_decide_disposition(), that is, scsi_check_sense(), on the sense
data obtained with REQUEST SENSE, and scsi_check_sense() sets the SCSI
midlayer internal byte of the result for some sense codes, e.g.
SCSIML_STAT_TGT_FAILURE for ILLEGAL REQUEST with ASC 0x20 (INVALID
COMMAND OPERATION CODE) or 0x24 (INVALID FIELD IN CDB), or
SCSIML_STAT_MED_ERROR for MEDIUM ERROR with ASC 0x11 (UNRECOVERED READ
ERROR). For such commands, atapi_qc_complete() keeps the result as is and
the command completes with a GOOD status byte, even though it failed and
valid sense data is available.

As a result, passthrough users see these failed ATAPI commands as
successful. For example, with the emulated IDE CD-ROM drive of QEMU and
no medium loaded, a PLAY AUDIO MSF command issued with SG_IO completes
with status 0x00 (and no DRIVER_SENSE) instead of 0x02 (CHECK CONDITION)
with sense key ILLEGAL REQUEST, ASC/ASCQ 0x20/0x00, and the CDROM ioctls
CDROMPLAYTRKIND, CDROMSUBCHNL, CDROMPAUSE, CDROMRESUME, CDROMPLAYMSF and
CDROM_GET_MCN return 0 instead of -ENOMEDIUM or -EOPNOTSUPP.

Fix this by setting the status byte to SAM_STAT_CHECK_CONDITION whenever
the host byte is not set. Use set_status_byte() rather than overwriting
the whole result, so that the SCSI midlayer internal byte set by
scsi_check_sense() is preserved, as ata_scsi_qc_complete() already does
for ATA commands.

Fixes: 2e1d2e65e773 ("ata: libata-scsi: terminate deferred commands on time out")
Cc: stable@vger.kernel.org
Suggested-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Hengyu Liang <hengyul@cs.unc.edu>
---
Changes in v2:
- Only set the status byte with set_status_byte() instead of overwriting
  cmd->result, so that the SCSI midlayer internal byte set by
  scsi_check_sense() is preserved (suggested by Niklas).
- Link to v1: https://lore.kernel.org/r/20260924180414.2102946-1-hengyul@cs.unc.edu

 drivers/ata/libata-scsi.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index 8f9aa97a519d..fb5517d51095 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -3059,10 +3059,15 @@ static void atapi_qc_complete(struct ata_queued_cmd *qc)
 		if (qc->cdb[0] == ALLOW_MEDIUM_REMOVAL && qc->dev->sdev)
 			qc->dev->sdev->locked = 0;
 
-		if (cmd->result)
-			ata_scsi_qc_done(qc, false, 0);
-		else
-			ata_scsi_qc_done(qc, true, SAM_STAT_CHECK_CONDITION);
+		/*
+		 * Report CHECK CONDITION unless the command was terminated
+		 * with a host byte set. Only set the status byte, so that the
+		 * SCSI midlayer internal byte, which scsi_check_sense() may
+		 * have set from the sense data, is preserved.
+		 */
+		if (get_host_byte(cmd) == DID_OK)
+			set_status_byte(cmd, SAM_STAT_CHECK_CONDITION);
+		ata_scsi_qc_done(qc, false, 0);
 		goto schedule_deferred;
 	}
 
-- 
2.53.0