Linux kernel stable tree (mirror) https://git.radix-linux.su/kernel/linux.git/atom?h=v3.16.61 2018-10-21T07:45:38+00:00 2018-10-21T07:45:38+00:00 Alan Cox alan@llwyncelyn.cymru 2017-06-02T12:49:30+00:00 urn:sha1:a6a35a2a03c2fecc1d6dbf552a262fa7321b7adf commit 8a8dabf2dd68caff842d38057097c23bc514ea6e upstream. Historically the N_TTY driver could never fail but this has become broken over time. Rather than trying to rewrite half the ldisc layer to fix the breakage introduce a second level of fallback with an N_NULL ldisc which cannot fail, and thus restore the guarantees required by the ldisc layer. We still try and fail to N_TTY first. It's much more useful to find yourself back in your old ldisc (first attempt) or in N_TTY (second attempt), and while I'm not aware of any code out there that makes those assumptions it's good to drive(r) defensively. Signed-off-by: Alan Cox <alan@linux.intel.com> Reported-by: Dmitry Vyukov <dvyukov@google.com> Tested-by: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 2012-10-13T09:46:48+00:00 David Howells dhowells@redhat.com 2012-10-13T09:46:48+00:00 urn:sha1:607ca46e97a1b6594b29647d98a32d545c24bdff Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Michael Kerrisk <mtk.manpages@gmail.com> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Dave Jones <davej@redhat.com>