[libvirt] [PATCH 11/14] rpc: virnetserver: Fix race on srv->nclients_unauth
John Ferlan
jferlan at redhat.com
Fri Dec 15 18:16:20 UTC 2017
On 12/12/2017 06:36 AM, Marc Hartmayer wrote:
> There is a race between virNetServerProcessClients (main thread) and
> remoteDispatchAuthList/remoteDispatchAuthPolkit/remoteSASLFinish (worker
> thread) that can lead to decrementing srv->nclients_unauth when it's
> zero. Since virNetServerCheckLimits relies on the value
> srv->nclients_unauth the underrun causes libvirtd to stop accepting
> new connections forever.
>
> Example race scenario (assuming libvirtd is using policykit and the
> client is privileged):
> 1. The client calls the RPC remoteDispatchAuthList =>
> remoteDispatchAuthList is executed on a worker thread (Thread
> T1). We're assuming now the execution stops for some time before
> the line 'virNetServerClientSetAuth(client, 0)'
> 2. The client closes the connection irregularly. This causes the
> event loop to wake up and virNetServerProcessClient to be
> called (on the main thread T0). During the
> virNetServerProcessClients the srv lock is hold. The condition
> virNetServerClientNeedAuth(client) will be checked and as the
> authentication is not finished right now
> virNetServerTrackCompletedAuthLocked(srv) will be called =>
> --srv->nclients_unauth => 0
> 3. The Thread T1 continues, marks the client as authenticated, and
> calls virNetServerTrackCompletedAuthLocked(srv) =>
> --srv->nclients_unauth => --0 => wrap around as nclient_unauth is
> unsigned
> 4. virNetServerCheckLimits(srv) will disable the services forever
>
> To fix it, add an auth_pending field to the client struct so that it
> is now possible to determine if the authentication process has already
> been handled for this client.
>
> Setting the authentication method to none for the client in
> virNetServerProcessClients is not a proper way to indicate that the
> counter has been decremented, as this would imply that the client is
> authenticated.
>
> Additionally, adjust the existing test cases for this new field.
>
> Signed-off-by: Marc Hartmayer <mhartmay at linux.vnet.ibm.com>
> Reviewed-by: Boris Fiuczynski <fiuczy at linux.vnet.ibm.com>
> ---
> src/libvirt_remote.syms | 2 +
> src/rpc/virnetserver.c | 28 ++++++++++++--
> src/rpc/virnetserverclient.c | 44 +++++++++++++++++++++-
> src/rpc/virnetserverclient.h | 2 +
> .../virnetdaemondata/output-data-admin-nomdns.json | 4 ++
> .../output-data-admin-server-names.json | 4 ++
> .../virnetdaemondata/output-data-anon-clients.json | 2 +
> tests/virnetdaemondata/output-data-client-ids.json | 2 +
> .../output-data-client-timestamp.json | 2 +
> .../output-data-initial-nomdns.json | 2 +
> tests/virnetdaemondata/output-data-initial.json | 2 +
> .../output-data-no-keepalive-required.json | 4 ++
> 12 files changed, 92 insertions(+), 6 deletions(-)
>
Ah... the patch I've been waiting for ;-)... What caused me to
initially look at this series is because I have bz related to some
possible sort of timing problem with TLS authentication, so I figured
reviewing a series related to this code would help me understand the
flow a bit better.
In any case, I think perhaps this can be split into two patches - one
that just sets/clears the auth_pending and then what's leftover as the fix.
> diff --git a/src/libvirt_remote.syms b/src/libvirt_remote.syms
> index 7fcae970484d..cef2794e1122 100644
> --- a/src/libvirt_remote.syms
> +++ b/src/libvirt_remote.syms
> @@ -138,6 +138,7 @@ virNetServerClientGetUNIXIdentity;
> virNetServerClientImmediateClose;
> virNetServerClientInit;
> virNetServerClientInitKeepAlive;
> +virNetServerClientIsAuthPendingLocked;
> virNetServerClientIsClosedLocked;
> virNetServerClientIsLocal;
> virNetServerClientIsSecure;
> @@ -152,6 +153,7 @@ virNetServerClientRemoteAddrStringURI;
> virNetServerClientRemoveFilter;
> virNetServerClientSendMessage;
> virNetServerClientSetAuthLocked;
> +virNetServerClientSetAuthPendingLocked;
> virNetServerClientSetCloseHook;
> virNetServerClientSetDispatcher;
> virNetServerClientStartKeepAlive;
> diff --git a/src/rpc/virnetserver.c b/src/rpc/virnetserver.c
> index 72105cd9318f..6dd673ff3b23 100644
> --- a/src/rpc/virnetserver.c
> +++ b/src/rpc/virnetserver.c
> @@ -286,7 +286,7 @@ int virNetServerAddClient(virNetServerPtr srv,
> srv->clients[srv->nclients-1] = virObjectRef(client);
>
> virObjectLock(client);
> - if (virNetServerClientNeedAuthLocked(client))
> + if (virNetServerClientIsAuthPendingLocked(client))
> virNetServerTrackPendingAuthLocked(srv);
> virObjectUnlock(client);
>
> @@ -738,6 +738,25 @@ int virNetServerSetTLSContext(virNetServerPtr srv,
>
>
> /**
> + * virNetServerSetClientAuthCompletedLocked:
> + * @srv: server must be locked by the caller
> + * @client: client must be locked by the caller
> + *
> + * Sets on the client that the authentication is no longer pending and
> + * tracks on @srv that the authentication of this @client has been
> + * completed.
If the client authentication was pending, clear that pending and update
the server tracking.
> + */
> +static void
> +virNetServerSetClientAuthCompletedLocked(virNetServerPtr srv, virNetServerClientPtr client)
One line for each argument.
> +{
> + if (virNetServerClientIsAuthPendingLocked(client)) {
> + virNetServerClientSetAuthPendingLocked(client, false);
> + virNetServerTrackCompletedAuthLocked(srv);
> + }
> +}
> +
> +
> +/**
> * virNetServerSetClientAuthenticated:
> * @srv: server must be unlocked
> * @client: client must be unlocked
> @@ -752,7 +771,7 @@ virNetServerSetClientAuthenticated(virNetServerPtr srv, virNetServerClientPtr cl
> virObjectLock(srv);
> virObjectLock(client);
> virNetServerClientSetAuthLocked(client, VIR_NET_SERVER_SERVICE_AUTH_NONE);
> - virNetServerTrackCompletedAuthLocked(srv);
> + virNetServerSetClientAuthCompletedLocked(srv, client);
> virNetServerCheckLimits(srv);
> virObjectUnlock(client);
> virObjectUnlock(srv);
> @@ -870,8 +889,9 @@ virNetServerProcessClients(virNetServerPtr srv)
> if (virNetServerClientIsClosedLocked(client)) {
> VIR_DELETE_ELEMENT(srv->clients, i, srv->nclients);
>
> - if (virNetServerClientNeedAuthLocked(client))
> - virNetServerTrackCompletedAuthLocked(srv);
> + /* Mark the authentication for this client as no longer
> + * pending */
Some may say a superfluous comment... I'd probably say make it one line
/* Update server authentication tracking */
> + virNetServerSetClientAuthCompletedLocked(srv, client);
> virObjectUnlock(client);
>
> virNetServerCheckLimits(srv);
> diff --git a/src/rpc/virnetserverclient.c b/src/rpc/virnetserverclient.c
> index 6adc3ec3ec01..5224bc7de1d5 100644
> --- a/src/rpc/virnetserverclient.c
> +++ b/src/rpc/virnetserverclient.c
> @@ -71,6 +71,7 @@ struct _virNetServerClient
> bool delayedClose;
> virNetSocketPtr sock;
> int auth;
> + bool auth_pending;
> bool readonly;
> #if WITH_GNUTLS
> virNetTLSContextPtr tlsCtxt;
> @@ -375,6 +376,7 @@ static virNetServerClientPtr
> virNetServerClientNewInternal(unsigned long long id,
> virNetSocketPtr sock,
> int auth,
> + bool auth_pending,
> #ifdef WITH_GNUTLS
> virNetTLSContextPtr tls,
> #endif
> @@ -384,6 +386,12 @@ virNetServerClientNewInternal(unsigned long long id,
> {
> virNetServerClientPtr client;
>
> + /* If the used authentication method implies that the new client
> + * is automatically authenticated, the authentication cannot be
> + * pending */
> + if (auth_pending && virNetServerClientAuthMethodImpliesAuthenticated(auth))
^^^^^^
Why check twice? I'm not clear on the need for this check. The setting
of auth_pending is based on @auth in the caller or perhaps the value of
auth_pending already. If there's some sort of check to be made perhaps
it's in ExecRestart.
Also, if we returned NULL here without some sort of error, then couldn't
we get the libvirt failed for some reason error message which is always
not fun to track down.
> + return NULL;
> +
> if (virNetServerClientInitialize() < 0)
> return NULL;
>
> @@ -393,6 +401,7 @@ virNetServerClientNewInternal(unsigned long long id,
> client->id = id;
> client->sock = virObjectRef(sock);
> client->auth = auth;
> + client->auth_pending = auth_pending;
> client->readonly = readonly;
> #ifdef WITH_GNUTLS
> client->tlsCtxt = virObjectRef(tls);
> @@ -440,6 +449,7 @@ virNetServerClientPtr virNetServerClientNew(unsigned long long id,
> {
> virNetServerClientPtr client;
> time_t now;
> + bool auth_pending = !virNetServerClientAuthMethodImpliesAuthenticated(auth);
I think it's much easier for readability to have result be auth !=
VIR_NET_SERVER_SERVICE_AUTH_NONE instead of this call... Perhaps even
easier to find all instances of AUTH_NONE.
>
> VIR_DEBUG("sock=%p auth=%d tls=%p", sock, auth,
> #ifdef WITH_GNUTLS
> @@ -454,7 +464,7 @@ virNetServerClientPtr virNetServerClientNew(unsigned long long id,
> return NULL;
> }
>
> - if (!(client = virNetServerClientNewInternal(id, sock, auth,
> + if (!(client = virNetServerClientNewInternal(id, sock, auth, auth_pending,
> #ifdef WITH_GNUTLS
> tls,
> #endif
> @@ -486,7 +496,7 @@ virNetServerClientPtr virNetServerClientNewPostExecRestart(virJSONValuePtr objec
> virNetServerClientPtr client = NULL;
> virNetSocketPtr sock;
> int auth;
> - bool readonly;
> + bool readonly, auth_pending;
> unsigned int nrequests_max;
> unsigned long long id;
> long long timestamp;
> @@ -496,6 +506,17 @@ virNetServerClientPtr virNetServerClientNewPostExecRestart(virJSONValuePtr objec
> _("Missing auth field in JSON state document"));
> return NULL;
> }
> +
> + if (!virJSONValueObjectHasKey(object, "auth_pending")) {
> + auth_pending = !virNetServerClientAuthMethodImpliesAuthenticated(auth);
same here - since not found in .json, then set based on auth !=
AUTH_NONE would be just clearer I think.
> + } else {
> + if (virJSONValueObjectGetBoolean(object, "auth_pending", &auth_pending) < 0) {
> + virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> + _("Malformed auth_pending field in JSON state document"));
> + return NULL;
> + }
> + }
> +
> if (virJSONValueObjectGetBoolean(object, "readonly", &readonly) < 0) {
> virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> _("Missing readonly field in JSON state document"));
> @@ -544,6 +565,7 @@ virNetServerClientPtr virNetServerClientNewPostExecRestart(virJSONValuePtr objec
> if (!(client = virNetServerClientNewInternal(id,
> sock,
> auth,
> + auth_pending,
> #ifdef WITH_GNUTLS
> NULL,
> #endif
> @@ -592,6 +614,8 @@ virJSONValuePtr virNetServerClientPreExecRestart(virNetServerClientPtr client)
>
> if (virJSONValueObjectAppendNumberInt(object, "auth", client->auth) < 0)
> goto error;
> + if (virJSONValueObjectAppendBoolean(object, "auth_pending", client->auth_pending) < 0)
> + goto error;
> if (virJSONValueObjectAppendBoolean(object, "readonly", client->readonly) < 0)
> goto error;
> if (virJSONValueObjectAppendNumberUint(object, "nrequests_max", client->nrequests_max) < 0)
> @@ -1545,6 +1569,22 @@ virNetServerClientNeedAuth(virNetServerClientPtr client)
> }
>
>
> +/* The caller must hold the lock for @client */
> +void
> +virNetServerClientSetAuthPendingLocked(virNetServerClientPtr client, bool auth_pending)
One line per argument
John
> +{
> + client->auth_pending = auth_pending;
> +}
> +
> +
> +/* The caller must hold the lock for @client */
> +bool
> +virNetServerClientIsAuthPendingLocked(virNetServerClientPtr client)
> +{
> + return client->auth_pending;
> +}
> +
> +
> static void
> virNetServerClientKeepAliveDeadCB(void *opaque)
> {
> diff --git a/src/rpc/virnetserverclient.h b/src/rpc/virnetserverclient.h
> index 19f20b808284..f608682dc600 100644
> --- a/src/rpc/virnetserverclient.h
> +++ b/src/rpc/virnetserverclient.h
> @@ -148,6 +148,8 @@ int virNetServerClientSendMessage(virNetServerClientPtr client,
>
> bool virNetServerClientNeedAuth(virNetServerClientPtr client);
> bool virNetServerClientNeedAuthLocked(virNetServerClientPtr client);
> +bool virNetServerClientIsAuthPendingLocked(virNetServerClientPtr client);
> +void virNetServerClientSetAuthPendingLocked(virNetServerClientPtr client, bool auth_pending);
>
> int virNetServerClientGetTransport(virNetServerClientPtr client);
> int virNetServerClientGetInfo(virNetServerClientPtr client,
> diff --git a/tests/virnetdaemondata/output-data-admin-nomdns.json b/tests/virnetdaemondata/output-data-admin-nomdns.json
> index fc960f02cee7..d6d02163e282 100644
> --- a/tests/virnetdaemondata/output-data-admin-nomdns.json
> +++ b/tests/virnetdaemondata/output-data-admin-nomdns.json
> @@ -41,6 +41,7 @@
> {
> "id": 1,
> "auth": 1,
> + "auth_pending": true,
> "readonly": true,
> "nrequests_max": 15,
> "sock": {
> @@ -53,6 +54,7 @@
> {
> "id": 2,
> "auth": 2,
> + "auth_pending": true,
> "readonly": true,
> "nrequests_max": 66,
> "sock": {
> @@ -105,6 +107,7 @@
> {
> "id": 1,
> "auth": 1,
> + "auth_pending": true,
> "readonly": true,
> "nrequests_max": 15,
> "sock": {
> @@ -117,6 +120,7 @@
> {
> "id": 2,
> "auth": 2,
> + "auth_pending": true,
> "readonly": true,
> "nrequests_max": 66,
> "sock": {
> diff --git a/tests/virnetdaemondata/output-data-admin-server-names.json b/tests/virnetdaemondata/output-data-admin-server-names.json
> index fc960f02cee7..d6d02163e282 100644
> --- a/tests/virnetdaemondata/output-data-admin-server-names.json
> +++ b/tests/virnetdaemondata/output-data-admin-server-names.json
> @@ -41,6 +41,7 @@
> {
> "id": 1,
> "auth": 1,
> + "auth_pending": true,
> "readonly": true,
> "nrequests_max": 15,
> "sock": {
> @@ -53,6 +54,7 @@
> {
> "id": 2,
> "auth": 2,
> + "auth_pending": true,
> "readonly": true,
> "nrequests_max": 66,
> "sock": {
> @@ -105,6 +107,7 @@
> {
> "id": 1,
> "auth": 1,
> + "auth_pending": true,
> "readonly": true,
> "nrequests_max": 15,
> "sock": {
> @@ -117,6 +120,7 @@
> {
> "id": 2,
> "auth": 2,
> + "auth_pending": true,
> "readonly": true,
> "nrequests_max": 66,
> "sock": {
> diff --git a/tests/virnetdaemondata/output-data-anon-clients.json b/tests/virnetdaemondata/output-data-anon-clients.json
> index 9f1c63504a1b..cb6005bfe68c 100644
> --- a/tests/virnetdaemondata/output-data-anon-clients.json
> +++ b/tests/virnetdaemondata/output-data-anon-clients.json
> @@ -41,6 +41,7 @@
> {
> "id": 1,
> "auth": 1,
> + "auth_pending": true,
> "readonly": true,
> "nrequests_max": 15,
> "sock": {
> @@ -53,6 +54,7 @@
> {
> "id": 2,
> "auth": 2,
> + "auth_pending": true,
> "readonly": true,
> "nrequests_max": 66,
> "sock": {
> diff --git a/tests/virnetdaemondata/output-data-client-ids.json b/tests/virnetdaemondata/output-data-client-ids.json
> index 43c61cc46ec7..2b1663d4f8c6 100644
> --- a/tests/virnetdaemondata/output-data-client-ids.json
> +++ b/tests/virnetdaemondata/output-data-client-ids.json
> @@ -41,6 +41,7 @@
> {
> "id": 2,
> "auth": 1,
> + "auth_pending": true,
> "readonly": true,
> "nrequests_max": 15,
> "sock": {
> @@ -53,6 +54,7 @@
> {
> "id": 3,
> "auth": 2,
> + "auth_pending": true,
> "readonly": true,
> "nrequests_max": 66,
> "sock": {
> diff --git a/tests/virnetdaemondata/output-data-client-timestamp.json b/tests/virnetdaemondata/output-data-client-timestamp.json
> index b706c147ed0e..e8c8e9a991d9 100644
> --- a/tests/virnetdaemondata/output-data-client-timestamp.json
> +++ b/tests/virnetdaemondata/output-data-client-timestamp.json
> @@ -41,6 +41,7 @@
> {
> "id": 1,
> "auth": 1,
> + "auth_pending": true,
> "readonly": true,
> "nrequests_max": 15,
> "conn_time": 1234567890,
> @@ -54,6 +55,7 @@
> {
> "id": 2,
> "auth": 2,
> + "auth_pending": true,
> "readonly": true,
> "nrequests_max": 66,
> "conn_time": 1234567890,
> diff --git a/tests/virnetdaemondata/output-data-initial-nomdns.json b/tests/virnetdaemondata/output-data-initial-nomdns.json
> index ca6b99553754..167aef8d295e 100644
> --- a/tests/virnetdaemondata/output-data-initial-nomdns.json
> +++ b/tests/virnetdaemondata/output-data-initial-nomdns.json
> @@ -41,6 +41,7 @@
> {
> "id": 1,
> "auth": 1,
> + "auth_pending": true,
> "readonly": true,
> "nrequests_max": 15,
> "sock": {
> @@ -53,6 +54,7 @@
> {
> "id": 2,
> "auth": 2,
> + "auth_pending": true,
> "readonly": true,
> "nrequests_max": 66,
> "sock": {
> diff --git a/tests/virnetdaemondata/output-data-initial.json b/tests/virnetdaemondata/output-data-initial.json
> index a8df6336c316..3281e868d7aa 100644
> --- a/tests/virnetdaemondata/output-data-initial.json
> +++ b/tests/virnetdaemondata/output-data-initial.json
> @@ -42,6 +42,7 @@
> {
> "id": 1,
> "auth": 1,
> + "auth_pending": true,
> "readonly": true,
> "nrequests_max": 15,
> "sock": {
> @@ -54,6 +55,7 @@
> {
> "id": 2,
> "auth": 2,
> + "auth_pending": true,
> "readonly": true,
> "nrequests_max": 66,
> "sock": {
> diff --git a/tests/virnetdaemondata/output-data-no-keepalive-required.json b/tests/virnetdaemondata/output-data-no-keepalive-required.json
> index fc960f02cee7..d6d02163e282 100644
> --- a/tests/virnetdaemondata/output-data-no-keepalive-required.json
> +++ b/tests/virnetdaemondata/output-data-no-keepalive-required.json
> @@ -41,6 +41,7 @@
> {
> "id": 1,
> "auth": 1,
> + "auth_pending": true,
> "readonly": true,
> "nrequests_max": 15,
> "sock": {
> @@ -53,6 +54,7 @@
> {
> "id": 2,
> "auth": 2,
> + "auth_pending": true,
> "readonly": true,
> "nrequests_max": 66,
> "sock": {
> @@ -105,6 +107,7 @@
> {
> "id": 1,
> "auth": 1,
> + "auth_pending": true,
> "readonly": true,
> "nrequests_max": 15,
> "sock": {
> @@ -117,6 +120,7 @@
> {
> "id": 2,
> "auth": 2,
> + "auth_pending": true,
> "readonly": true,
> "nrequests_max": 66,
> "sock": {
>
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