A bug in the SysV tty drivers
terry
terry at wsccs.UUCP
Tue Feb 23 14:40:09 AEST 1988
Why is it that when I get a System V port open using the partial open hack,
it works OK until I get a HI to LO transition of the carrier detect, at which
point it will continue to transmit out the port, but not read? In addition,
since there is no signal to a proccess whose controlling tty is NOT the tty
that the CD was lost on (ie: cu, Kermit, TERM), I can't tell it's gone (except
from the fact that I now get an EOF when I attempt to read it... it comes
back with a correctly terminated read which read 0 characters), and if someone
then calls in, it crashes the system (isn't this *NOT* supposed to be possible,
no matter what mistakes the user makes, short of being priveledged and doing
something like kludging /dev/mem, etc.). I can demonstrate this on the
following operating systems:
AT&T 3B1 (PC 7300) All UNIX versions
AT&T 3B2 All UNIX versions
Microport UNIX 386 version only
ISC Unix 386 verion (only one I had access to)
L/F Technologies cubix 5.2 (?)
All NCR boxes
All Unisys boxes
Arete 1100
Burroughs XE550
Doesn't anybody test these things?
I am using a modified dial.c (simpleist case, apparently) to
just 1) open the port and 2) sit there forever, constantly
queing single character reads.
PLEASE PLEASE PLEASE PLEASE PLEASE fix this so I don't get any more calls.
I can pin-point it within 10 lines of code in tty.c, but since I no longer am
a student at the college I went to, I cannot access the source any more without
incurring a 65,000 dollar fee (isn't that what they're charging these days?).
I can't post a fix (same reason). I won't post a source that does it (if you
can't hack one yourself, you probably shouldn't be doing it anyway) because the
dial.c is proprietary.
If you can mail me, and prove you're AT&T, I'll talk, but don't expect a quick
reply; I'm too busy answering calls.
PS: we have a workaround, but I shouldn't have to work around.
Mail from AT&T welcome at:
| Terry Lambert UUCP: ...!decvax!utah-cs!century!terry |
| @ Century Software or : ...utah-cs!uplherc!sp7040!obie!wsccs!terry |
| SLC, Utah |
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