On Tue, Jan 15, 2013 at 5:26 PM, Jiri Slaby <[email protected]> wrote: > Now that login from util-linux is forced to drop all references to a > TTY which it wants to hangup (to reach reference count 1) we are > seeing issues with telnet. When login closes its last reference to the > slave PTY, it also resets packet mode on the *master* side. And we > have a race here. > > What telnet does is fork+exec of `login'. Then there are two > scenarios: > * `login' closes the slave TTY and resets thus master's packet mode, > but even now telnet properly sets the mode, or > * `telnetd' sets packet mode on the master, `login' closes the slave > TTY and resets master's packet mode. > > The former case is OK. However the latter happens in much more cases, > by the order of magnitude to be precise. So when one tries to login to > such a messed telnet setup, they see the following: > inux login: > ogin incorrect > > Note the missing first letters -- telnet thinks it is still in the > packet mode, so when it receives "linux login" from `login', it > considers "l" as the type of the packet and strips it. > > SuS does not mention how the implementation should behave. Both BSDs I > checked (Free and Net) do not reset the flag upon the last close. > > By this I am resurrecting an old bug, see References. We are hitting > it regularly now, i.e. with updated util-linux, ergo login. > > Here, I am changing a behavior introduced back in 2.1 times. It would > better have a long time testing before goes upstream. > > Signed-off-by: Jiri Slaby <[email protected]> > Cc: Mauro Carvalho Chehab <[email protected]> > Cc: Bryan Mason <[email protected]> > References: https://lkml.org/lkml/2009/11/11/223 > References: https://bugzilla.redhat.com/show_bug.cgi?id=504703 > References: https://bugzilla.novell.com/show_bug.cgi?id=797042
Shouldn't this be CC'd to stable? josh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
