Messages in this thread | | | Subject | Re: [PATCH 2/2] xen-netfront: Fix race between device setup and open | From | Ross Lagerwall <> | Date | Thu, 11 Jan 2018 15:49:07 +0000 |
| |
On 01/11/2018 03:26 PM, David Miller wrote: > From: Ross Lagerwall <ross.lagerwall@citrix.com> > Date: Thu, 11 Jan 2018 09:36:38 +0000 > >> When a netfront device is set up it registers a netdev fairly early on, >> before it has set up the queues and is actually usable. A userspace tool >> like NetworkManager will immediately try to open it and access its state >> as soon as it appears. The bug can be reproduced by hotplugging VIFs >> until the VM runs out of grant refs. It registers the netdev but fails >> to set up any queues (since there are no more grant refs). In the >> meantime, NetworkManager opens the device and the kernel crashes trying >> to access the queues (of which there are none). >> >> Fix this in two ways: >> * For initial setup, register the netdev much later, after the queues >> are setup. This avoids the race entirely. >> * During a suspend/resume cycle, the frontend reconnects to the backend >> and the queues are recreated. It is possible (though highly unlikely) to >> race with something opening the device and accessing the queues after >> they have been destroyed but before they have been recreated. Extend the >> region covered by the rtnl semaphore to protect against this race. There >> is a possibility that we fail to recreate the queues so check for this >> in the open function. >> >> Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com> > > Where is patch 1/2 and the 0/2 header posting which explains what this > patch series is doing, how it is doing it, and why it is doing it that > way? >
I've now added CC'd netdev on the other two.
Cheers, -- Ross Lagerwall
| |