Re: [libvirt] Potential segfault in udev driver
2010/1/25 Dave Allan <dallan(a)redhat.com>:
On 01/25/2010 06:37 AM, Daniel P. Berrange wrote:
>
> On Sun, Jan 24, 2010 at 11:07:59PM +0100, Matthias Bolte wrote:
>>
>> udevDeviceMonitorStartup registers udevEventHandleCallback as event
>> handle, but doesn't store the returned watch id to remove it later on.
>> Also it's not clear to me whether the event handle should be register
>> for the whole lifetime of the udev driver instance or just for the
>> udevEnumerateDevices call.
>
> The handler should be active for the lifetime of libvirtd, since the
> udev driver has to detect hotplug/unplug events over time.
>
>>
>> If for example the call to udevSetupSystemDev [1] fails
>> udevDeviceMonitorShutdown is called to cleanup, but
>> udevEventHandleCallback is still registered and may be called when
>> driverState is NULL again, resulting in a segfault in
>> udevEventHandleCallback.
>>
>> So to solve this the udevEventHandleCallback event handle must be
>> removed at the appropriate place.
>
> Yes, sounds like its needs to be removed in the failure path there
Matthias,
Indeed, that's correct--can you submit a patch?
Dave
Yes, im going to do that.
One last question. The udev driver stores the udev monitor handle in
the private data pointer of the gloval driver state variable.
driverState->privateData = udev_monitor;
To solve the event handle problem we need to store the watch id
returned by virEventAddHandle somewhere. We could either add a new
private data struct to hold the udev_monitor pointer and the watch id,
or store the watch id variable globally side by side with the driver
state variable. I prefer the first option, because it's cleaner and
the DRV_STATE_UDEV_MONITOR define allows for changing the storage
location of the udev_monitor pointer easily.
Matthias