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GNetworkMonitorNetlink question




The netlink code in GNetworkMonitorNetlink ignores all netlink replies
that are not from uid 0. It has done so since initial merging (bug
#620932), and there is even a comment in that bug from lennart that
describes how to use netlink:

  e) for (;;) { recvmsg(fd, data...); if (SCM_CREDENTIALS.uid != 0)  
     continue; process(data...); }

This is breaking for me in user namespaces where uid 0 is not mapped (it
gets mapped to overflowuid), but just the user id. In this case we don't
even return an error. I.e this code:

  sender = g_credentials_get_unix_user (creds, NULL);
  if (sender != 0)
    goto done;
 
Does not set retval to FALSE, which means we ignore all replies and then
wait forever as we never looked at the the final NLMSG_DONE message.

Is there really a risk of another user sending a message over netlink
here?

-- 
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
 Alexander Larsson                                            Red Hat, Inc 
       alexl@xxxxxxxxxx            alexander.larsson@xxxxxxxxx 
He's a scarfaced guerilla astronaut moving from town to town, helping 
folk in trouble. She's a virginal hip-hop angel from the wrong side of 
the tracks. They fight crime! 

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