[PATCH 03/14] scsi: core: Do not truncate INQUIRY data on modern devices

From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: linux-scsi@vger.kernel.org
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Subject: [PATCH 03/14] scsi: core: Do not truncate INQUIRY data on modern devices
Date: Wed,  2 Mar 2022 00:35:48 -0500	[thread overview]
Message-ID: <20220302053559.32147-4-martin.petersen@oracle.com> (raw)
In-Reply-To: <20220302053559.32147-1-martin.petersen@oracle.com>

Low-level device drivers have had the ability to limit the size of an
INQUIRY for many years. This made sense for a wide variety of legacy
devices. However, we are unnecessarily truncating the INQUIRY response
for many modern devices. This prevents us from consulting fields
beyond the first 36 bytes.

If a device reports that it supports a larger INQUIRY response, and
the device also reports that it implements SPC-4 or newer, allow the
larger INQUIRY to proceed.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
---
 drivers/scsi/scsi_scan.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index f4e6c68ac99e..95bf9a1f35ce 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -728,7 +728,17 @@ static int scsi_probe_lun(struct scsi_device *sdev, unsigned char *inq_result,
 		if (pass == 1) {
 			if (BLIST_INQUIRY_36 & *bflags)
 				next_inquiry_len = 36;
-			else if (sdev->inquiry_len)
+			/*
+			 * LLD specified a maximum sdev->inquiry_len
+			 * but device claims it has more data. Capping
+			 * the length only makes sense for legacy
+			 * devices. If a device supports SPC-4 (2014)
+			 * or newer, assume that it is safe to ask for
+			 * as much as the device says it supports.
+			 */
+			else if (sdev->inquiry_len &&
+				 response_len > sdev->inquiry_len &&
+				 (inq_result[2] & 0x7) < 6) /* SPC-4 */
 				next_inquiry_len = sdev->inquiry_len;
 			else
 				next_inquiry_len = response_len;
-- 
2.32.0

