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Re: [libvirt] [PATCH v3 2/2] libxl: add tunnelled migration support



On 02/16/2017 02:57 PM, John Ferlan wrote:
> On 02/16/2017 09:26 AM, Joao Martins wrote:
>> On 02/16/2017 11:47 AM, John Ferlan wrote:
>>> FYI: Couple of Coverity issues resulted from these patches.
>>>
>>>>  int
>>>> +libxlDomainMigrationPrepareTunnel3(virConnectPtr dconn,
>>>> +                                   virStreamPtr st,
>>>> +                                   virDomainDefPtr *def,
>>>> +                                   const char *cookiein,
>>>> +                                   int cookieinlen,
>>>> +                                   unsigned int flags)
>>>> +{
>>>> +    libxlMigrationCookiePtr mig = NULL;
>>>> +    libxlDriverPrivatePtr driver = dconn->privateData;
>>>> +    virDomainObjPtr vm = NULL;
>>>> +    libxlMigrationDstArgs *args = NULL;
>>>> +    virThread thread;
>>>> +    bool taint_hook = false;
>>>> +    libxlDomainObjPrivatePtr priv = NULL;
>>>> +    char *xmlout = NULL;
>>>> +    int dataFD[2] = { -1, -1 };
>>>> +    int ret = -1;
>>>> +
>>>> +    if (libxlDomainMigrationPrepareAny(dconn, def, cookiein, cookieinlen,
>>>> +                                       &mig, &xmlout, &taint_hook) < 0)
>>>
>>> Coverity notes that '@mig' will be leaked in this case when "if
>>> (!cookiein || !cookieinlen) {" is true in libxlMigrationEatCookie and
>>> failures from libxlDomainMigrationPrepareAny don't free it.
>>
>> /nods. This diff should do then? It covers both cases I think.
> 
> What about:
> 
>     args->migcookie = mig;
> 
> 
> and then successful virThreadCreate(&thread, false,
> libxlDoMigrateReceive, args) where 'args' is unref'd, but the cookie
> isn't free'd.
> 
> Certainly you wouldn't want to free the cookie and then let the thread
> use it!
\facepalm - you're right.

> So I think the libxlMigrationCookieFree needs to be done in the error:
> label and in the thread cleanup. Also after you assign @mig to
> migcookie, set 'mig = NULL';
Yeap, let me send that in a follow-up patch shortly.
The thread cleanup you mean libxlDoMigrateReceive right? There I think we could
simply move unref args to cleanup label (which would free the cookie). But
probably should go into a separate patch as it seems to be an issue to all
migration paths.

>> diff --git a/src/libxl/libxl_migration.c b/src/libxl/libxl_migration.c
>> index ba1ca5c..6a7d458 100644
>> --- a/src/libxl/libxl_migration.c
>> +++ b/src/libxl/libxl_migration.c
>> @@ -637,6 +637,7 @@ libxlDomainMigrationPrepareTunnel3(virConnectPtr dconn,
>>      }
>>
>>   done:
>> +    libxlMigrationCookieFree(mig);
>>      if (vm)
>>          virObjectUnlock(vm);
>>
>>
>>
>>>> +        goto error;
>>>> +
>>>> +    if (!(vm = virDomainObjListAdd(driver->domains, *def,
>>>> +                                   driver->xmlopt,
>>>> +                                   VIR_DOMAIN_OBJ_LIST_ADD_LIVE |
>>>> +                                   VIR_DOMAIN_OBJ_LIST_ADD_CHECK_LIVE,
>>>> +                                   NULL)))
>>>> +        goto error;
>>>> +
>>>> +    *def = NULL;
>>>> +    priv = vm->privateData;
>>>> +
>>>> +    if (taint_hook) {
>>>> +        /* Domain XML has been altered by a hook script. */
>>>> +        priv->hookRun = true;
>>>> +    }
>>>> +
>>>> +    /*
>>>> +     * The data flow of tunnel3 migration in the dest side:
>>>> +     * stream -> pipe -> recvfd of libxlDomainStartRestore
>>>> +     */
>>>> +    if (pipe(dataFD) < 0)
>>>> +        goto error;
>>>> +
>>>> +    /* Stream data will be written to pipeIn */
>>>> +    if (virFDStreamOpen(st, dataFD[1]) < 0)
>>>> +        goto error;
>>>> +    dataFD[1] = -1; /* 'st' owns the FD now & will close it */
>>>> +
>>>> +    if (libxlMigrationDstArgsInitialize() < 0)
>>>> +        goto error;
>>>> +
>>>> +    if (!(args = virObjectNew(libxlMigrationDstArgsClass)))
>>>> +        goto error;
>>>> +
>>>> +    args->conn = dconn;
>>>> +    args->vm = vm;
>>>> +    args->flags = flags;
>>>> +    args->migcookie = mig;
>>>> +    /* Receive from pipeOut */
>>>> +    args->recvfd = dataFD[0];
>>>> +    args->nsocks = 0;
>>>> +    if (virThreadCreate(&thread, false, libxlDoMigrateReceive, args) < 0) {
>>>> +        virReportError(VIR_ERR_OPERATION_FAILED, "%s",
>>>> +                       _("Failed to create thread for receiving migration data"));
>>>> +        goto error;
>>>> +    }
>>>> +
>>>> +    ret = 0;
>>>> +    goto done;
>>>> +
>>>> + error:
>>>> +    VIR_FORCE_CLOSE(dataFD[1]);
>>>> +    VIR_FORCE_CLOSE(dataFD[0]);
>>>> +    virObjectUnref(args);
>>>> +    /* Remove virDomainObj from domain list */
>>>> +    if (vm) {
>>>> +        virDomainObjListRemove(driver->domains, vm);
>>>> +        vm = NULL;
>>>> +    }
>>>> +
>>>> + done:
>>>> +    if (vm)
>>>> +        virObjectUnlock(vm);
>>>> +
>>>> +    return ret;
>>>> +}
>>>
>>> [...]
>>>
>>>> +
>>>> +static int
>>>> +libxlMigrationStartTunnel(libxlDriverPrivatePtr driver,
>>>> +                          virDomainObjPtr vm,
>>>> +                          unsigned long flags,
>>>> +                          virStreamPtr st,
>>>> +                          struct libxlTunnelControl *tc)
>>>> +{
>>>> +    libxlTunnelMigrationThread *arg = NULL;
>>>> +    int ret = -1;
>>>> +
>>>> +    if (VIR_ALLOC(tc) < 0)
>>>> +        goto out;
>>>> +
>>>> +    tc->dataFD[0] = -1;
>>>> +    tc->dataFD[1] = -1;
>>>> +    if (pipe(tc->dataFD) < 0) {
>>>> +        virReportError(errno, "%s", _("Unable to make pipes"));
>>>
>>> Coverity notes that failures would cause a leak for @tc (I assume here
>>> and of course if virThreadCreate fails.  Perhaps the 'best' way to
>>> handle that would be to set tc = NULL after ThreadCreate success and
>>> just call libxlMigrationStopTunnel in "out:"...
>>
>> But libxlMigrationStopTunnel is always called (hence should be freeing @tc),
>> whether libxlMigrationStartTunnel failed or not. How about this?
>>
>> @@ -907,8 +908,9 @@ libxlMigrationStartTunnel(libxlDriverPrivatePtr driver,
>>                            virDomainObjPtr vm,
>>                            unsigned long flags,
>>                            virStreamPtr st,
>> -                          struct libxlTunnelControl *tc)
>> +                          struct libxlTunnelControl **tnl)
>>  {
>> +    struct libxlTunnelControl *tc = *tnl;
> 
> This doesn't do much... since @tc would be allocated below and *tnl
> wouldn't be updated... Thus, the following is better:
> 
>     if (VIR_ALLOC(tc) < 0)
>         goto out;
>     *tnl = tc;
> 
OK.

>>      libxlTunnelMigrationThread *arg = NULL;
>>      int ret = -1;
>>
>> @@ -1045,7 +1047,7 @@ libxlDoMigrateP2P(libxlDriverPrivatePtr driver,
>>
>>      VIR_DEBUG("Perform3 uri=%s", NULLSTR(uri_out));
>>      if (flags & VIR_MIGRATE_TUNNELLED)
>> -        ret = libxlMigrationStartTunnel(driver, vm, flags, st, tc);
>> +        ret = libxlMigrationStartTunnel(driver, vm, flags, st, &tc);
>>      else
>>          ret = libxlDomainMigrationPerform(driver, vm, NULL, NULL,
>>                                            uri_out, NULL, flags);
>>


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