[PATCH][RFC] storage: Simplify condition to reject bad target in usb_stor_control_thread()

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Hi,

This follows on from something I mentioned in my recent post "[PATCH]
storage: Don't scan target 7 for SCM USB-SCSI converters".

In drivers/usb/storage/usb.c, usb_stor_control_thread():
	/* reject if target != 0 or if LUN is higher than
	 * the maximum known LUN
	 */
	else if (us->srb->device->id &&
			!(us->fflags & US_FL_SCM_MULT_TARG)) {
		usb_stor_dbg(us, "Bad target number (%d:%llu)\n",
			     us->srb->device->id,
			     us->srb->device->lun);
		us->srb->result = DID_BAD_TARGET << 16;
	}

	else if (us->srb->device->lun > us->max_lun) {
		usb_stor_dbg(us, "Bad LUN (%d:%llu)\n",
	...

The condition (us->srb->device->id && !(us->fflags & US_FL_SCM_MULT_TARG))
means:
 - If not SCM_MULT_TARG, reject if us->srb->device->id is non-zero. That
   works for the usual case.
 - If SCM_MULT_TARG, never reject. Hmm...

Would it be better/clearer to change the condition to simply
  (us->srb->device->id >= host->max_id)

Then the command is rejected if us->srb->device->id is too large, and works
for the SCM_MULT_TARG case too. (host->max_id is 1 for the non-SCM_MULT_TARG
case.) Plus the condition matches nicely with the later LUN check. Untested
patch below.


Signed-off-by: Mark Knibbs <markk@xxxxxxxxxxx>

diff -up linux-3.17-rc6/drivers/usb/storage/usb.c.orig linux-3.17-rc6/drivers/usb/storage/usb.c     
--- linux-3.17-rc6/drivers/usb/storage/usb.c.orig	2014-09-21 23:43:02.000000000 +0100
+++ linux-3.17-rc6/drivers/usb/storage/usb.c	2014-09-24 13:09:55.000000000 +0100
@@ -342,11 +342,10 @@ static int usb_stor_control_thread(void
 			us->srb->result = DID_ERROR << 16;
 		}
 
-		/* reject if target != 0 or if LUN is higher than
+		/* reject if target is invalid or if LUN is higher than
 		 * the maximum known LUN
 		 */
-		else if (us->srb->device->id &&
-				!(us->fflags & US_FL_SCM_MULT_TARG)) {
+		else if (us->srb->device->id >= host->max_id) {
 			usb_stor_dbg(us, "Bad target number (%d:%llu)\n",
 				     us->srb->device->id,
 				     us->srb->device->lun);
--
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