Commit 12b322ac authored Jun 19, 2015 by Palik, Imre Committed by David S. Miller Jun 23, 2015

xen-netback: fix a BUG() during initialization



Commit edafc132 ("xen-netback: making the bandwidth limiter runtime settable")
introduced the capability to change the bandwidth rate limit at runtime.
But it also introduced a possible crashing bug.

If netback receives two XenbusStateConnected without getting the
hotplug-status watch firing in between, then it will try to register the
watches for the rate limiter again.  But this triggers a BUG() in the watch
registration code.

The fix modifies connect() to remove the possibly existing packet-rate
watches before trying to install those watches.  This behaviour is in line
with how connect() deals with the hotplug-status watch.

Signed-off-by: Imre Palik <imrep@amazon.de>
Cc: Matt Wilson <msw@amazon.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 754bc547

drivers/net/xen-netback/xenbus.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -681,6 +681,9 @@ static int xen_register_watchers(struct xenbus_device dev, struct xenvif vif)
		char *node;
		unsigned maxlen = strlen(dev->nodename) + sizeof("/rate");

		if (vif->credit_watch.node)
		return -EADDRINUSE;

		node = kmalloc(maxlen, GFP_KERNEL);
		if (!node)
		return -ENOMEM;
		@@ -770,6 +773,7 @@ static void connect(struct backend_info *be)
		}

		xen_net_read_rate(dev, &credit_bytes, &credit_usec);
		xen_unregister_watchers(be->vif);
		xen_register_watchers(dev, be->vif);
		read_xenbus_vif_flags(be);