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remoteDispatchAuthPolkit: Fix lock ordering deadlock if client closes connection during auth 

Locks in following text:
A: virNetServer
B: virNetServerClient
C: daemonClientPrivate

'virNetServerSetClientAuthenticated' locks A then B

'remoteDispatchAuthPolkit' calls 'virNetServerSetClientAuthenticated'
while holding C.

If a client closes its connection 'virNetServerProcessClients' with the
lock A and B locked will call 'virNetServerClientCloseLocked' which will
try to dispose of the 'client' private data by:

  ref(b);
  unlock(b);
  remoteClientFreePrivateCallbacks();
  lock(b);
  unref(b);

Unfortunately remoteClientFreePrivateCallbacks() tries lock C.

Thus the locks are held in the following order:

 polkit auth: C -> A
 connection close: A -> C

causing a textbook-example deadlock. To resolve it we can simply drop
lock 'C' before calling 'virNetServerSetClientAuthenticated' as the lock
is not needed any more.

Resolves: https://issues.redhat.com/browse/RHEL-20337
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
This commit is contained in:
Peter Krempa 2024-01-17 15:55:35 +01:00
parent f95675fdbb
commit c697aff8a1
1 changed files with 42 additions and 40 deletions
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4
src/remote/remote_daemon_dispatch.c
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@ -3979,8 +3979,8 @@ remoteDispatchAuthPolkit(virNetServer *server,
struct daemonClientPrivate *priv =
virNetServerClientGetPrivateData(client);
int rv;
VIR_LOCK_GUARD lock = virLockGuardLock(&priv->lock);
VIR_WITH_MUTEX_LOCK_GUARD(&priv->lock) {
action = virNetServerClientGetReadonly(client) ?
"org.libvirt.unix.monitor" :
"org.libvirt.unix.manage";
@ -4022,7 +4022,9 @@ remoteDispatchAuthPolkit(virNetServer *server,
VIR_INFO("Policy allowed action %s from pid %lld, uid %d",
action, (long long) callerPid, callerUid);
ret->complete = 1;
}
/* this must be called with the private data mutex unlocked */
virNetServerSetClientAuthenticated(server, client);
return 0;