On Tue, 20 Aug 2019, Hong Cho wrote: > Hi, > > We recently upgraded OpenSSH from 7.5p1 to 8.0p1, and received a report > that there was a behavioral differences where the ssh session did not > disconnect after a remote background command execution. For example, "ssh > user@xxxxxxxxxxx 'tail -f /var/xxx &' > > After looking at the debug logs and comparing the code, it seems there was > a bug in the portable version during the adaptation of the 1.367 change > (refactoring) of channels.c. > > The OpenBSD version looks correct, but for the portable version, the exit > condition of channel_handle_efd_read() didn't get converted correctly, but > somehow got copy-and-pasted from the rfd version. I couldn't find the > change history for the portable version, so I can't when/how this happened. > > This should make the "force" condition the same as before the refactoring > of the portable version of channels.c. > > --- /tmp/tmp.48415.39 2019-08-19 19:24:29.000000000 -0700 > +++ crypto/openssh/channels.c 2019-08-19 19:19:39.000000000 -0700 > @@ -2103,7 +2103,15 @@ channel_handle_efd_read(struct ssh *ssh, > ssize_t len; > int r, force; > > + force = c->detach_close; > - force = c->isatty && c->detach_close && c->istate != CHAN_INPUT_CLOSED; This change wasn't a refactor or a mistake, but an intentional bugfix for https://bugzilla.mindrot.org/show_bug.cgi?id=2071 Anyway, I don't see any change in behaviour for your testcase between OpenSSH 7.2 and 8.0 on Linux - they both wait for the tail process to terminate before dropping the connection. Applying your suggested change doesn't make any difference either. The behaviour at close has always been a tricky area and there are divergences between portable OpenSSH and OpenBSD for a long time, driven by how more SysV-ish systems like Linux differ from BSDs. BTW line-by-line change history can be extracted using "git blame" on a checkout of the portable OpenSSH git tree. -d _______________________________________________ openssh-unix-dev mailing list openssh-unix-dev@xxxxxxxxxxx https://lists.mindrot.org/mailman/listinfo/openssh-unix-dev
