scsi: sg: fix SG_DXFER_FROM_DEV transfers

Johannes Thumshirn · martinkpetersen · commit 68c59fcea1f2 · 2017-07-12T17:17:18.000-04:00
SG_DXFER_FROM_DEV transfers do not necessarily have a dxferp as we set it to NULL for the old sg_io read/write interface, but must have a length bigger than 0. This fixes a regression introduced by commit 28676d8 ("scsi: sg: check for valid direction before starting the request") Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de> Fixes: 28676d8 ("scsi: sg: check for valid direction before starting the request") Reported-by: Chris Clayton <chris2553@googlemail.com> Tested-by: Chris Clayton <chris2553@googlemail.com> Cc: Douglas Gilbert <dgilbert@interlog.com> Reviewed-by: Hannes Reinecke <hare@suse.com> Tested-by: Chris Clayton <chris2553@googlemail.com> Acked-by: Douglas Gilbert <dgilbert@interlog.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
@@ -758,8 +758,11 @@ static bool sg_is_valid_dxfer(sg_io_hdr_t *hp)
 		if (hp->dxferp || hp->dxfer_len > 0)
 			return false;
 		return true;
-	case SG_DXFER_TO_DEV:
 	case SG_DXFER_FROM_DEV:
+		if (hp->dxfer_len < 0)
+			return false;
+		return true;
+	case SG_DXFER_TO_DEV:
 	case SG_DXFER_TO_FROM_DEV:
 		if (!hp->dxferp || hp->dxfer_len == 0)
 			return false;
