[PATCH] hwmon: drivetemp: Fix driver producing garbage data when SCSI errors occur

[Daniil Stas <daniil.stas@posteo.net>]

scsi_execute_cmd() function can return both negative (linux codes) and
positive (scsi_cmnd result field) error codes.

Currently the driver just passes error codes of scsi_execute_cmd() to
hwmon core, which is incorrect because hwmon only checks for negative
error codes. This leads to hwmon reporting uninitialized data to
userspace in case of SCSI errors (for example if the disk drive was
disconnected).

This patch checks scsi_execute_cmd() output and returns -EIO if it's
error code is positive.

Signed-off-by: Daniil Stas <daniil.stas@posteo.net>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Chris Healy <cphealy@gmail.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: linux-kernel@vger.kernel.org
Cc: linux-scsi@vger.kernel.org
Cc: linux-ide@vger.kernel.org
Cc: linux-hwmon@vger.kernel.org
---

Although I see there is scsi_status_is_good() function, which probably
means that not all scsi result codes are errors? I don't know scsi
protocol much, so maybe someone else can check it.
The error code that i see when the drive is physically disconnected: 0x00030000.

 drivers/hwmon/drivetemp.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/hwmon/drivetemp.c b/drivers/hwmon/drivetemp.c
index 6bdd21aa005a..fdf1d3b3b5a5 100644
--- a/drivers/hwmon/drivetemp.c
+++ b/drivers/hwmon/drivetemp.c
@@ -192,8 +192,11 @@ static int drivetemp_scsi_command(struct drivetemp_data *st,
 	scsi_cmd[12] = lba_high;
 	scsi_cmd[14] = ata_command;
 
-	return scsi_execute_cmd(st->sdev, scsi_cmd, op, st->smartdata,
-				ATA_SECT_SIZE, HZ, 5, NULL);
+	int err = scsi_execute_cmd(st->sdev, scsi_cmd, op, st->smartdata,
+				   ATA_SECT_SIZE, HZ, 5, NULL);
+	if (err > 0)
+		err = -EIO;
+	return err;
 }
 
 static int drivetemp_ata_command(struct drivetemp_data *st, u8 feature,
-- 
2.47.1