hwmon: (drivetemp) Fix driver producing garbage data when SCSI errors occur

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.

Fixes: 5b46903 ("hwmon: Driver for disk and solid state drives with temperature sensors")
Signed-off-by: Daniil Stas <[email protected]>
Cc: Guenter Roeck <[email protected]>
Cc: Chris Healy <[email protected]>
Cc: Linus Walleij <[email protected]>
Cc: Martin K. Petersen <[email protected]>
Cc: Bart Van Assche <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]
[groeck: Avoid inline variable declaration for portability]
Signed-off-by: Guenter Roeck <[email protected]>

Author: Daniil Stas

drivers/hwmon/drivetemp.c

@@ -165,6 +165,7 @@ static int drivetemp_scsi_command(struct drivetemp_data *st,
 {
 	u8 scsi_cmd[MAX_COMMAND_SIZE];
 	enum req_op op;
+	int err;
 
 	memset(scsi_cmd, 0, sizeof(scsi_cmd));
 	scsi_cmd[0] = ATA_16;
@@ -192,8 +193,11 @@ 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);
+	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,