prelink should not mess with running executables

[Sam Varshavchik]

Chris Adams writes:

> Once upon a time, Sam Varshavchik <mrsam at courier-mta.com> said:
> > A means for authenticating a filesystem domain socket's peer. Receive the
> > peer's credentials, then check /proc/pid/exe and /proc/self/exe. If they're
> > same, the daemon is talking to another instance of itself.
>
> Is there anything that actually does that and depends on the result?
> Such a check would be inherently racey.

The only race condition exists in this situation, that I can see, is an  
impostor making the filesystem domain connection, sending the credentials  
under the original pid, forking, and have the original process exec the  
process being impersonated.

Setting aside the likelyhood of a succesfull exploit, the race is  
preventable simply by requiring the peer resend its credentials, after  
validating the peer's pathname, and verifying that the pid did not change.

Don't panic.

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