[PATCH] [SCSI] sd: make error handling more robust (v2)

[Tony Battersby <tonyb@cybernetics.com>]

This patch fixes a problem with some out-of-spec SCSI disks that report
hardware or medium errors incorrectly.  Without the patch, the kernel
may silently ignore a failed write command or return corrupted data on a
failed read command.

Signed-off-by: Tony Battersby <tonyb@cybernetics.com>
---

This is a simplified version of the original patch that fixes just the
problem at hand, without trying to handle other theoretical out-of-spec
cases.

Applies to kernels 2.6.18 - 2.6.24-git10+.

--- linux-2.6.24-git10/drivers/scsi/sd.c.orig	2008-02-01 11:24:37.000000000 -0500
+++ linux-2.6.24-git10/drivers/scsi/sd.c	2008-02-01 11:26:12.000000000 -0500
@@ -990,6 +990,8 @@ static int sd_done(struct scsi_cmnd *SCp
 		/* This computation should always be done in terms of
 		 * the resolution of the device's medium.
 		 */
+		if (bad_lba < start_lba)
+			goto out;
 		good_bytes = (bad_lba - start_lba)*SCpnt->device->sector_size;
 		break;
 	case RECOVERED_ERROR: