From: Damien Le Moal <damien.lemoal@wdc.com>
Date: Fri, 20 Aug 2021 16:02:54 +0900
Subject: [PATCH] scsi: core: Fix scsi_mode_select() buffer length handling
Git-commit: a7d6840bed0c2b16ac3071b74b5fcf08fc488241
Patch-mainline: v5.16-rc1
References: jsc#PED-1559

The MODE SELECT(6) command allows handling mode page buffers that are up to
255 bytes, including the 4 byte header needed in front of the page
buffer. For requests larger than this limit, automatically use the MODE
SELECT(10) command.

In both cases, since scsi_mode_select() adds the mode select page header,
checks on the buffer length value must include this header size to avoid
overflows of the command CDB allocation length field.

While at it, use put_unaligned_be16() for setting the header block
descriptor length and CDB allocation length when using MODE SELECT(10).

[mkp: fix MODE SENSE vs. MODE SELECT confusion]

Link: https://lore.kernel.org/r/20210820070255.682775-3-damien.lemoal@wdc.com
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: Hannes Reinecke <hare@suse.com>
---
 drivers/scsi/scsi_lib.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 701d8e8480f2..dcf105287a76 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2026,8 +2026,15 @@ scsi_mode_select(struct scsi_device *sdev, int pf, int sp, int modepage,
 	memset(cmd, 0, sizeof(cmd));
 	cmd[1] = (pf ? 0x10 : 0) | (sp ? 0x01 : 0);
 
-	if (sdev->use_10_for_ms) {
-		if (len > 65535)
+	/*
+	 * Use MODE SELECT(10) if the device asked for it or if the mode page
+	 * and the mode select header cannot fit within the maximumm 255 bytes
+	 * of the MODE SELECT(6) command.
+	 */
+	if (sdev->use_10_for_ms ||
+	    len + 4 > 255 ||
+	    data->block_descriptor_length > 255) {
+		if (len > 65535 - 8)
 			return -EINVAL;
 		real_buffer = kmalloc(8 + len, GFP_KERNEL);
 		if (!real_buffer)
@@ -2040,15 +2047,13 @@ scsi_mode_select(struct scsi_device *sdev, int pf, int sp, int modepage,
 		real_buffer[3] = data->device_specific;
 		real_buffer[4] = data->longlba ? 0x01 : 0;
 		real_buffer[5] = 0;
-		real_buffer[6] = data->block_descriptor_length >> 8;
-		real_buffer[7] = data->block_descriptor_length;
+		put_unaligned_be16(data->block_descriptor_length,
+				   &real_buffer[6]);
 
 		cmd[0] = MODE_SELECT_10;
-		cmd[7] = len >> 8;
-		cmd[8] = len;
+		put_unaligned_be16(len, &cmd[7]);
 	} else {
-		if (len > 255 || data->block_descriptor_length > 255 ||
-		    data->longlba)
+		if (data->longlba)
 			return -EINVAL;
 
 		real_buffer = kmalloc(4 + len, GFP_KERNEL);
-- 
2.35.3