xen/blkfront: Fix crash if backend doesn't follow the right states.
We have split the setting up of all the resources in two steps:
1) talk_to_blkback - which figures out the num_ring_pages (from
the default value of zero), sets up shadow and so
2) blkfront_connect - does the real part of filling out the
internal structures.
The problem is if we bypass the 1) step and go straight to 2)
and call blkfront_setup_indirect where we use the macro
BLK_RING_SIZE - which returns an negative value (because
sz is zero - since num_ring_pages is zero - since it has never
been set).
We can fix this by making sure that we always have called
talk_to_blkback before going to blkfront_connect.
Or we could set in blkfront_probe info->nr_ring_pages = 1
to have a default value. But that looks odd - as we haven't
actually negotiated any ring size.
This patch changes XenbusStateConnected state to detect if
we haven't done the initial handshake - and if so continue
on as if were in XenbusStateInitWait state.
We also roll the error recovery (freeing the structure) into
talk_to_blkback error path - which is safe since that function
is only called from blkback_changed.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index f3d0d47..8a8dc91 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -1867,6 +1867,9 @@
destroy_blkring:
blkif_free(info, 0);
+ kfree(info);
+ dev_set_drvdata(&dev->dev, NULL);
+
return err;
}
@@ -2453,11 +2456,8 @@
case XenbusStateInitWait:
if (dev->state != XenbusStateInitialising)
break;
- if (talk_to_blkback(dev, info)) {
- kfree(info);
- dev_set_drvdata(&dev->dev, NULL);
+ if (talk_to_blkback(dev, info))
break;
- }
case XenbusStateInitialising:
case XenbusStateInitialised:
case XenbusStateReconfiguring:
@@ -2466,6 +2466,10 @@
break;
case XenbusStateConnected:
+ if (dev->state != XenbusStateInitialised) {
+ if (talk_to_blkback(dev, info))
+ break;
+ }
blkfront_connect(info);
break;