Subject: [rddp] Re: security-draft : 7.4.6 - Using Multiple STags

From: Caitlin Bestler <[email-masked]>
Date: Tue, 24 Jun 2003 21:49:57 -0500

>7.4.6  Using Multiple Stags to access the same buffer  
>
>   Multiple STags accessing the same buffer at the same time can result 
>   in unintentional information disclosure. When one STag has remote 
>   read access enabled and a different STag has remote write access 
>   enabled to the same buffer, it is possible for one connection to 
>   view the contents that have been written by another Remote Peer. 
>   This is not a problem when all of the STags accessing the buffer 
>   have only remote read enabled. For Trust Models NS-NT, S-NT, S-LT it 
>   is RECOMMENDED that multiple Remote Peers not be granted access to 
>   the same buffer through different STags at the same time. A buffer 
>   should be exposed to only one Untrusted Remote Peer at a time to 
>   ensure that no information disclosure occurs between peers.

This strikes me as highly redundant data that might dissuade some
legitimate usage of multiple STags.

The general rule is that the contents of *any* advertised buffer
are logically void *until* completion.

That applies to local acces, *or* any remotely enabled access.

A distributed ULP that has chosen to be "trusting" (i.e. that it
is only required to work when all participants follow the upper
layer protocol) could easily have a buffer that is exposed to
multiple participants. However, it would be the ULPs responsibility
to ensure that at most one process was attempting to update the
buffer at any time, and that nobody was trying to read it during
an update.

That is a general rule for *any* multi-threaded, let alone,
multi-processor or distributed application. It has nothing to
do with RDMA. I really don't see the value of including it. Use
of unitialized pointers is a bad idea too.

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