3.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Peter Hurley <[email protected]>

commit d4855e1fc03c2bb32dd64badf51cec5a2a26ab2a upstream.

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 <[email protected]>
Signed-off-by: Peter Hurley <[email protected]>
Tested-by: Heorhi Valakhanovich <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

---
 drivers/tty/tty_io.c |    1 +
 1 file changed, 1 insertion(+)

--- 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);
 
 


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