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authorJiri Slaby <jslaby@suse.cz>2013-01-15 23:26:22 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-01-15 22:49:36 -0800
commitb81273a132177edd806476b953f6afeb17b786d5 (patch)
treec893995f2fcebb58660f98461787f33f54f3d043 /drivers/tty
parent37c44b52b102eb144fe4487f4a7ac39a70caee19 (diff)
TTY: do not reset master's packet mode
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 <jslaby@suse.cz> Cc: Mauro Carvalho Chehab <mchehab@redhat.com> Cc: Bryan Mason <bmason@redhat.com> 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 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty')
-rw-r--r--drivers/tty/pty.c1
1 files changed, 0 insertions, 1 deletions
diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index 4ec11f326d6d..40ff2bf68b43 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -47,7 +47,6 @@ static void pty_close(struct tty_struct *tty, struct file *filp)
/* Review - krefs on tty_link ?? */
if (!tty->link)
return;
- tty->link->packet = 0;
set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
wake_up_interruptible(&tty->link->read_wait);
wake_up_interruptible(&tty->link->write_wait);