diff options
authorKonrad Rzeszutek Wilk <>2015-12-18 16:28:53 -0500
committerKonrad Rzeszutek Wilk <>2016-01-04 12:21:26 -0500
commitc31ecf6c126dbc7f30234eaf6c4a079649a38de7 (patch)
parent93bb277f97a6d319361766bde228717faf4abdeb (diff)
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 <>
1 files changed, 8 insertions, 4 deletions
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index f3d0d4758641..8a8dc91c39f7 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -1867,6 +1867,9 @@ again:
blkif_free(info, 0);
+ kfree(info);
+ dev_set_drvdata(&dev->dev, NULL);
return err;
@@ -2453,11 +2456,8 @@ static void blkback_changed(struct xenbus_device *dev,
case XenbusStateInitWait:
if (dev->state != XenbusStateInitialising)
- if (talk_to_blkback(dev, info)) {
- kfree(info);
- dev_set_drvdata(&dev->dev, NULL);
+ if (talk_to_blkback(dev, info))
- }
case XenbusStateInitialising:
case XenbusStateInitialised:
case XenbusStateReconfiguring:
@@ -2466,6 +2466,10 @@ static void blkback_changed(struct xenbus_device *dev,
case XenbusStateConnected:
+ if (dev->state != XenbusStateInitialised) {
+ if (talk_to_blkback(dev, info))
+ break;
+ }