Bug#129559: libpager robustness

[Marcus Brinkmann]

On Thu, Jan 17, 2002 at 10:01:47AM -0800, Thomas Bushnell, BSG wrote:
> Marcus Brinkmann <Marcus.Brinkmann@ruhr-uni-bochum.de> writes:
> > Neal reported this bug to me a while ago.  If you send an invalid message (a
> > message with an unhandled msgid) to a pager, it will miss out on this msg id
> > and the seqno stuff doesn't catch up anymore.  The result is a deadlock
> > waiting for this msg id when the next valid message is processed.
> 
> You betcha.  It is basically assumed (quite unsecurely) that the user
> will not be "mean" with the pager port he's given.

I remember reading about this in the TODO list etc.  Are there any concrete
other unrobustnesses you remember?

BTW, I did not consider the return value too much, but just assumed that
returning the same as before would be fine.  I now verified that the return
value is ignored in mach_msg_server (in glibc), and that current practice
seems to be that the demux function returns 0 if it could not process the
message and 1 if it could and did.  As we are not processing the message,
but just synchronise our state, I don't see a problem (even semantically).

Thanks,
Marcus

-- 
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Marcus Brinkmann              GNU    http://www.gnu.org    marcus@gnu.org
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