compat_ioctl: scsi: handle HDIO commands from drivers

The ata_sas_scsi_ioctl() function implements a number of HDIO_* commands
for SCSI devices, it is used by all libata drivers as well as a few
drivers that support SAS attached SATA drives.

The only command that is not safe for compat ioctls here is
HDIO_GET_32BIT. Change the implementation to check for in_compat_syscall()
in order to do both cases correctly, and change all callers to use it
as both native and compat callback pointers, including the indirect
callers through sas_ioctl and ata_scsi_ioctl.

Reviewed-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index 58e09ff..eb2eb599 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -17,6 +17,7 @@
  *  - http://www.t13.org/
  */
 
+#include <linux/compat.h>
 #include <linux/slab.h>
 #include <linux/kernel.h>
 #include <linux/blkdev.h>
@@ -761,6 +762,10 @@ static int ata_ioc32(struct ata_port *ap)
 	return 0;
 }
 
+/*
+ * This handles both native and compat commands, so anything added
+ * here must have a compatible argument, or check in_compat_syscall()
+ */
 int ata_sas_scsi_ioctl(struct ata_port *ap, struct scsi_device *scsidev,
 		     unsigned int cmd, void __user *arg)
 {
@@ -773,6 +778,10 @@ int ata_sas_scsi_ioctl(struct ata_port *ap, struct scsi_device *scsidev,
 		spin_lock_irqsave(ap->lock, flags);
 		val = ata_ioc32(ap);
 		spin_unlock_irqrestore(ap->lock, flags);
+#ifdef CONFIG_COMPAT
+		if (in_compat_syscall())
+			return put_user(val, (compat_ulong_t __user *)arg);
+#endif
 		return put_user(val, (unsigned long __user *)arg);
 
 	case HDIO_SET_32BIT: