Date: Tue, 26 Sep 2006 14:13:18 -0400 From: "Brandon S. Allbery KF8NH" <allbery@ece.cmu.edu> To: "Magnus Ringman" <bmr@google.com> Cc: current@freebsd.org Subject: Re: What do you think ?: How should pseundo terminals behave ... Message-ID: <F0E30165-89B1-4A79-A376-615AF1655234@ece.cmu.edu> In-Reply-To: <4f674ca50609261109s78a26d3dh1dd0a6dc8c112ca2@mail.google.com> References: <20060926111452.J91466@godot.imp.ch> <0C4B0125-11AA-4BDB-A4E3-163A6194AB68@alumni.cwru.edu> <98FD6058-7220-48DB-AC24-F989FCB2AE11@ece.cmu.edu> <4f674ca50609261029s76432971yfc15171a3e89cb72@mail.google.com> <8EECEF0C-8C94-4A7C-862A-633F67D3D229@ece.cmu.edu> <4f674ca50609261109s78a26d3dh1dd0a6dc8c112ca2@mail.google.com>
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On Sep 26, 2006, at 14:09 , Magnus Ringman wrote: > On 9/26/06, Brandon S. Allbery KF8NH <allbery@ece.cmu.edu> wrote: >> I think that in many circumstances (and, as you note, implemented in >> other OSes), the correct behavior *is* to treat hangup as "backing >> device no longer exists" --- an older session should not leak into a >> newer one, it is a potential security hole and certainly a potential >> source of confusion. And if hardware ttys do it, I should think >> virtual ones should also do so for consistency. > > Methinks Sir has it the wrong way around! > Hangup on a hardware device -doesn't- void a program's access to the > device. It just (optionally) sends the process a SIGHUP. That is why > somebody (iirc, for SunOS < 5) invented vhangup(2) as a means for a > new session owner to insure it was the only process using the > terminal. I think you misunderstood: yes, physically you do not lose access, but for security reasons *logically you should*, and that is why vhangup() was invented. And, this being done, it is also a reasonable --- and, more to the point, consistent --- model for what happens when a pty slave loses its master (which *is* equivalent to physically losing access). -- brandon s. allbery [linux,solaris,freebsd,perl] allbery@kf8nh.com system administrator [openafs,heimdal,too many hats] allbery@ece.cmu.edu electrical and computer engineering, carnegie mellon university KF8NH
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