[libvirt] [PATCH 1/2] daemon: Fix segfault by reloading daemon right after start

[Daniel P. Berrange]

On Wed, Feb 18, 2015 at 04:24:31PM +0100, Pavel Hrdina wrote:
> Libvirt could crash with segfault if user issue "service reload" right
> after "service start". One possible way to crash libvirt is to run reload
> during initialization of QEMU driver.
> 
> It could happen when qemu driver will initialize qemu_driver_lock but
> don't have a time to set it's "config" and the SIGHUP arrives. The
> reload handler tries to get qemu_drv->config during "virStorageAutostart"
> and dereference it which ends with segfault.
> 
> Let's ignore all reload requests until all drivers are initialized.
> 
> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1179981
> 
> Signed-off-by: Pavel Hrdina <phrdina at redhat.com>
> ---
>  daemon/libvirtd.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/daemon/libvirtd.c b/daemon/libvirtd.c
> index 86accaa..835e7dc 100644
> --- a/daemon/libvirtd.c
> +++ b/daemon/libvirtd.c
> @@ -785,6 +785,11 @@ static void daemonReloadHandler(virNetServerPtr srv ATTRIBUTE_UNUSED,
>                                  siginfo_t *sig ATTRIBUTE_UNUSED,
>                                  void *opaque ATTRIBUTE_UNUSED)
>  {
> +    if (!driversInitialized) {
> +        VIR_WARN("Drivers are not initialized, reload ignored");
> +        return;
> +    }
> +
>      VIR_INFO("Reloading configuration on SIGHUP");
>      virHookCall(VIR_HOOK_DRIVER_DAEMON, "-",
>                  VIR_HOOK_DAEMON_OP_RELOAD, SIGHUP, "SIGHUP", NULL, NULL);

Why don't we just not register the reload handler until we get to the
point where it is safe. eg register it only after virStateInitialize
is complete, and unregister it before we call virStateCleanup.


Regards,
Daniel
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