From: Peter Hurley <peter@hurleysoftware.com>
Date: Tue, 19 Nov 2013 13:46:27 +0000 (-0500)
Subject: tty: Reset hupped state on open
X-Git-Tag: firefly_0821_release~176^2~4812^2~3
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=d4855e1fc03c2bb32dd64badf51cec5a2a26ab2a;p=firefly-linux-kernel-4.4.55.git

tty: Reset hupped state on open

A common security idiom is to hangup the current tty (via vhangup())
after forking but before execing a root shell. This hangs up any
existing opens which other processes may have and ensures subsequent
opens have the necessary permissions to open the root shell tty/pty.

Reset the TTY_HUPPED state after the driver has successfully
returned the opened tty (perform the reset while the tty is locked
to avoid racing with concurrent hangups).

Reported-by: Heorhi Valakhanovich <valahanovich@tut.by>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Cc: stable <stable@vger.kernel.org> # 3.12
Tested-by: Heorhi Valakhanovich <valahanovich@tut.by>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 3a1a01af9a80..c74a00ad7add 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2086,6 +2086,7 @@ retry_open:
 			filp->f_op = &tty_fops;
 		goto retry_open;
 	}
+	clear_bit(TTY_HUPPED, &tty->flags);
 	tty_unlock(tty);