[PATCH 3.12 118/212] tty: Reset hupped state on open (no replies)

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

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

From: Peter Hurley <peter@hurleysoftware.com>

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 <valahanovich@tut.by>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Tested-by: Heorhi Valakhanovich <valahanovich@tut.by>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
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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