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    network: prevent dnsmasq from listening on localhost · d66eb786
    Laine Stump 提交于
    This patch resolves the problem reported in:
    
       https://bugzilla.redhat.com/show_bug.cgi?id=886663
    
    The source of the problem was the fix for CVE 2011-3411:
    
       https://bugzilla.redhat.com/show_bug.cgi?id=833033
    
    which was originally committed upstream in commit
    753ff83a. That commit improperly
    removed the "--except-interface lo" from dnsmasq commandlines when
    --bind-dynamic was used (based on comments in the latter bug).
    
    It turns out that the problem reported in the CVE could be eliminated
    without removing "--except-interface lo", and removing it actually
    caused each instance of dnsmasq to listen on localhost on port 53,
    which created a new problem:
    
    If another instance of dnsmasq using "bind-interfaces" (instead of
    "bind-dynamic") had already been started (or if another instance
    started later used "bind-dynamic"), this wouldn't have any immediately
    visible ill effects, but if you tried to start another dnsmasq
    instance using "bind-interfaces" *after* starting any libvirt
    networks, the new dnsmasq would fail to start, because there was
    already another process listening on port 53.
    
    (Subsequent to the CVE fix, another patch changed the network driver
    to put dnsmasq options in a conf file rather than directly on the
    dnsmasq commandline, but preserved the same options.)
    
    This patch changes the network driver to *always* add
    "except-interface=lo" to dnsmasq conf files, regardless of whether we use
    bind-dynamic or bind-interfaces. This way no libvirt dnsmasq instances
    are listening on localhost (and the CVE is still fixed).
    
    The actual code change is miniscule, but must be propogated through all
    of the test files as well.
    d66eb786
bridge_driver.c 156.1 KB