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bus: Don't crash if bus_context_create_client_policy() fails

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If policy creation fails, we can't usefully leave a NULL policy in the
BusConnectionData. If we did, the next attempt to reload policy would
crash with a NULL dereference when we tried to unref it, or with
an assertion failure.

One situation in which we can legitimately fail to create a client policy
is an out-of-memory condition. Another is if we are unable to look up a
connection's supplementary groups with SO_PEERGROUPS, and also unable to
look up the connection's uid's groups in the system user database, for
example because it belongs to a user account that has been deleted (which
is sysadmin error, but can happen, particularly in automated test systems)
or because a service required by a Name Service Switch plugin has failed.

Keeping the last known policy is consistent with what happens to all
the connections that are after this one in iteration order: after we
early-return, all of those connections retain their previous policies
(which doesn't seem ideal either, but that's how this has always worked).

[smcv: Add commit message]
Co-authored-by: Simon McVittie <smcv@collabora.com>
Resolves: https://gitlab.freedesktop.org/dbus/dbus/-/issues/343
This commit is contained in:
Peter Benie 2023-06-23 11:51:00 +01:00 • committed by Simon McVittie
parent 3378792746
commit 63522f2887
1 changed files with 9 additions and 5 deletions
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14
bus/connection.c
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@ -1662,22 +1662,26 @@ bus_connections_reload_policy (BusConnections *connections,
link;
link = _dbus_list_get_next_link (&(connections->completed), link))
{
BusClientPolicy *policy;
connection = link->data;
d = BUS_CONNECTION_DATA (connection);
_dbus_assert (d != NULL);
_dbus_assert (d->policy != NULL);
bus_client_policy_unref (d->policy);
d->policy = bus_context_create_client_policy (connections->context,
connection,
error);
if (d->policy == NULL)
policy = bus_context_create_client_policy (connections->context,
connection,
error);
if (policy == NULL)
{
_dbus_verbose ("Failed to create security policy for connection %p\n",
connection);
_DBUS_ASSERT_ERROR_IS_SET (error);
return FALSE;
}
bus_client_policy_unref (d->policy);
d->policy = policy;
}
return TRUE;