Fix OpenSSH pty regression on close
authorBrian Bloniarz <brian.bloniarz@gmail.com>
Sun, 6 Mar 2016 21:16:30 +0000 (13:16 -0800)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Sun, 1 May 2016 20:22:54 +0000 (13:22 -0700)
commit0f40fbbcc34e093255a2b2d70b6b0fb48c3f39aa
treeedfa996be5ce50cd79dcfdfa96bb9d8490418660
parentd11df61853f1d45035b7f5a6702c9b48d5f09a49
Fix OpenSSH pty regression on close

OpenSSH expects the (non-blocking) read() of pty master to return
EAGAIN only if it has received all of the slave-side output after
it has received SIGCHLD. This used to work on pre-3.12 kernels.

This fix effectively forces non-blocking read() and poll() to
block for parallel i/o to complete for all ttys. It also unwinds
these changes:

1) f8747d4a466ab2cafe56112c51b3379f9fdb7a12
   tty: Fix pty master read() after slave closes

2) 52bce7f8d4fc633c9a9d0646eef58ba6ae9a3b73
   pty, n_tty: Simplify input processing on final close

3) 1a48632ffed61352a7810ce089dc5a8bcd505a60
   pty: Fix input race when closing

Inspired by analysis and patch from Marc Aurele La France <tsi@tuyoix.net>

Reported-by: Volth <openssh@volth.com>
Reported-by: Marc Aurele La France <tsi@tuyoix.net>
BugLink: https://bugzilla.mindrot.org/show_bug.cgi?id=52
BugLink: https://bugzilla.mindrot.org/show_bug.cgi?id=2492
Signed-off-by: Brian Bloniarz <brian.bloniarz@gmail.com>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Documentation/serial/tty.txt
drivers/tty/n_hdlc.c
drivers/tty/n_tty.c
drivers/tty/pty.c
drivers/tty/tty_buffer.c
include/linux/tty.h