From: Palik, Imre Date: Fri, 19 Jun 2015 12:21:51 +0000 (+0200) Subject: xen-netback: fix a BUG() during initialization X-Git-Tag: firefly_0821_release~176^2~1587^2~2^2~5 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=12b322ac85208de564ecf23aa754d796a91de21f;p=firefly-linux-kernel-4.4.55.git xen-netback: fix a BUG() during initialization Commit edafc132baac ("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 Cc: Matt Wilson Acked-by: Wei Liu Signed-off-by: David S. Miller --- diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c index 968787abf78d..ec383b0f5443 100644 --- a/drivers/net/xen-netback/xenbus.c +++ b/drivers/net/xen-netback/xenbus.c @@ -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);