[libvirt] [PATCH 11/14] rpc: virnetserver: Fix race on srv->nclients_unauth
Marc Hartmayer
mhartmay at linux.vnet.ibm.com
Tue Dec 12 11:36:33 UTC 2017
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(-)
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.
+ */
+static void
+virNetServerSetClientAuthCompletedLocked(virNetServerPtr srv, virNetServerClientPtr client)
+{
+ 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 */
+ 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))
+ 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);
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);
+ } 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)
+{
+ 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": {
--
2.13.4
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