On Tue, Jan 26, 2010 at 03:17:42AM +0100, Matthias Bolte wrote:
> 2010/1/25 Dave Allan <dallan@xxxxxxxxxx>:
> > On 01/25/2010 02:33 PM, Matthias Bolte wrote:
> >>
> >> 2010/1/25 Dave Allan<dallan@xxxxxxxxxx>:
> >>>
> >>> 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.
> >
> > Yes, I agree--a struct is the right approach. Thanks for doing this!
> >
> > Dave
> >
>
> Here's the patch. Maximilian Wilhelm tested it.
>
> Matthias
> From 07678696504179c70b987947061de2ff658e665c Mon Sep 17 00:00:00 2001
> From: Matthias Bolte <matthias.bolte@xxxxxxxxxxxxxx>
> Date: Tue, 26 Jan 2010 02:58:37 +0100
> Subject: [PATCH] udev: Remove event handle on shutdown
>
> This fixes a segfault when the event handler is called after shutdown
> when the global driver state is NULL again.
>
> Also fix a locking issue in an error path.
> ---
> src/node_device/node_device_udev.c | 49 +++++++++++++++++++++++++++---------
> src/node_device/node_device_udev.h | 4 ++-
> 2 files changed, 40 insertions(+), 13 deletions(-)
>
> diff --git a/src/node_device/node_device_udev.c b/src/node_device/node_device_udev.c
> index 2e459d1..a625d76 100644
> --- a/src/node_device/node_device_udev.c
> +++ b/src/node_device/node_device_udev.c
> @@ -41,6 +41,11 @@
>
> #define VIR_FROM_THIS VIR_FROM_NODEDEV
>
> +struct _udevPrivate {
> + struct udev_monitor *udev_monitor;
> + int watch;
> +};
> +
> static virDeviceMonitorStatePtr driverState = NULL;
>
> static int udevStrToLong_ull(char const *s,
> @@ -1354,12 +1359,18 @@ static int udevDeviceMonitorShutdown(void)
> {
> int ret = 0;
>
> + udevPrivate *priv = NULL;
> struct udev_monitor *udev_monitor = NULL;
> struct udev *udev = NULL;
>
> if (driverState) {
> -
> nodeDeviceLock(driverState);
> +
> + priv = driverState->privateData;
> +
> + if (priv->watch != -1)
> + virEventRemoveHandle(priv->watch);
> +
> udev_monitor = DRV_STATE_UDEV_MONITOR(driverState);
>
> if (udev_monitor != NULL) {
> @@ -1375,7 +1386,7 @@ static int udevDeviceMonitorShutdown(void)
> nodeDeviceUnlock(driverState);
> virMutexDestroy(&driverState->lock);
> VIR_FREE(driverState);
> -
> + VIR_FREE(priv);
> } else {
> ret = -1;
> }
> @@ -1534,18 +1545,28 @@ out:
>
> static int udevDeviceMonitorStartup(int privileged ATTRIBUTE_UNUSED)
> {
> + udevPrivate *priv = NULL;
> struct udev *udev = NULL;
> - struct udev_monitor *udev_monitor = NULL;
> int ret = 0;
>
> + if (VIR_ALLOC(priv) < 0) {
> + virReportOOMError(NULL);
> + ret = -1;
> + goto out;
> + }
> +
> + priv->watch = -1;
> +
> if (VIR_ALLOC(driverState) < 0) {
> virReportOOMError(NULL);
> + VIR_FREE(priv);
> ret = -1;
> goto out;
> }
>
> if (virMutexInit(&driverState->lock) < 0) {
> VIR_ERROR0("Failed to initialize mutex for driverState");
> + VIR_FREE(priv);
> VIR_FREE(driverState);
> ret = -1;
> goto out;
> @@ -1562,18 +1583,19 @@ static int udevDeviceMonitorStartup(int privileged ATTRIBUTE_UNUSED)
> udev = udev_new();
> udev_set_log_fn(udev, udevLogFunction);
>
> - udev_monitor = udev_monitor_new_from_netlink(udev, "udev");
> - if (udev_monitor == NULL) {
> + priv->udev_monitor = udev_monitor_new_from_netlink(udev, "udev");
> + if (priv->udev_monitor == NULL) {
> + VIR_FREE(priv);
> + nodeDeviceUnlock(driverState);
> VIR_ERROR0("udev_monitor_new_from_netlink returned NULL");
> ret = -1;
> goto out;
> }
>
> - udev_monitor_enable_receiving(udev_monitor);
> + udev_monitor_enable_receiving(priv->udev_monitor);
>
> /* udev can be retrieved from udev_monitor */
> - driverState->privateData = udev_monitor;
> - nodeDeviceUnlock(driverState);
> + driverState->privateData = priv;
>
> /* We register the monitor with the event callback so we are
> * notified by udev of device changes before we enumerate existing
> @@ -1583,14 +1605,17 @@ static int udevDeviceMonitorStartup(int privileged ATTRIBUTE_UNUSED)
> * enumeration. The alternative is to register the callback after
> * we enumerate, in which case we will fail to create any devices
> * that appear while the enumeration is taking place. */
> - if (virEventAddHandle(udev_monitor_get_fd(udev_monitor),
> - VIR_EVENT_HANDLE_READABLE,
> - udevEventHandleCallback,
> - NULL, NULL) == -1) {
> + priv->watch = virEventAddHandle(udev_monitor_get_fd(priv->udev_monitor),
> + VIR_EVENT_HANDLE_READABLE,
> + udevEventHandleCallback, NULL, NULL);
> + if (priv->watch == -1) {
> + nodeDeviceUnlock(driverState);
> ret = -1;
> goto out;
> }
>
> + nodeDeviceUnlock(driverState);
> +
> /* Create a fictional 'computer' device to root the device tree. */
> if (udevSetupSystemDev() != 0) {
> ret = -1;
> diff --git a/src/node_device/node_device_udev.h b/src/node_device/node_device_udev.h
> index 6c83412..8367494 100644
> --- a/src/node_device/node_device_udev.h
> +++ b/src/node_device/node_device_udev.h
> @@ -23,8 +23,10 @@
> #include <libudev.h>
> #include <stdint.h>
>
> +typedef struct _udevPrivate udevPrivate;
> +
> #define SYSFS_DATA_SIZE 4096
> -#define DRV_STATE_UDEV_MONITOR(ds) ((struct udev_monitor *)((ds)->privateData))
> +#define DRV_STATE_UDEV_MONITOR(ds) (((udevPrivate *)((ds)->privateData))->udev_monitor)
> #define DMI_DEVPATH "/sys/devices/virtual/dmi/id"
> #define DMI_DEVPATH_FALLBACK "/sys/class/dmi/id"
> #define PROPERTY_FOUND 0
ACK
Daniel
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