scsi: fix searching for an empty id

The conditions for detecting no free target or LUN were wrong.

The LUN loop was followed by an "if" condition that is never
true, because the loop is exited as soon as lun becomes equal
to bus->info->max_lun, and never becomes greater than it.

The target loop had a wrong condition (<= instead of <).  Once
this is fixed, the loop would fail in the same way as the LUN
loop.

The fix is to see whether scsi_device_find returned the device with the
last (channel, target, LUN) pair, and fail if so.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

hw/scsi-bus.c

diff --git a/hw/scsi-bus.c b/hw/scsi-bus.c
index 2cf2f0d..2cb5a18 100644
--- a/hw/scsi-bus.c
+++ b/hw/scsi-bus.c
@@ -132,6 +132,10 @@
         error_report("bad scsi device id: %d", dev->id);
         goto err;
     }
+    if (dev->lun != -1 && dev->lun > bus->info->max_lun) {
+        error_report("bad scsi device lun: %d", dev->lun);
+        goto err;
+    }
 
     if (dev->id == -1) {
         int id = -1;
@@ -140,8 +144,8 @@
         }
         do {
             d = scsi_device_find(bus, dev->channel, ++id, dev->lun);
-        } while (d && d->lun == dev->lun && id <= bus->info->max_target);
-        if (id > bus->info->max_target) {
+        } while (d && d->lun == dev->lun && id < bus->info->max_target);
+        if (d && d->lun == dev->lun) {
             error_report("no free target");
             goto err;
         }
@@ -151,14 +155,15 @@
         do {
             d = scsi_device_find(bus, dev->channel, dev->id, ++lun);
         } while (d && d->lun == lun && lun < bus->info->max_lun);
-        if (lun > bus->info->max_lun) {
+        if (d && d->lun == lun) {
             error_report("no free lun");
             goto err;
         }
         dev->lun = lun;
     } else {
         d = scsi_device_find(bus, dev->channel, dev->id, dev->lun);
-        if (dev->lun == d->lun && dev != d) {
+        assert(d);
+        if (d->lun == dev->lun && dev != d) {
             qdev_free(&d->qdev);
         }
     }
@@ -217,7 +222,7 @@
     int res = 0, unit;
 
     loc_push_none(&loc);
-    for (unit = 0; unit < bus->info->max_target; unit++) {
+    for (unit = 0; unit <= bus->info->max_target; unit++) {
         dinfo = drive_get(IF_SCSI, bus->busnr, unit);
         if (dinfo == NULL) {
             continue;