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 3a1a01a..c74a00a 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c
@@ -2086,6 +2086,7 @@ filp->f_op = &tty_fops; goto retry_open; } + clear_bit(TTY_HUPPED, &tty->flags); tty_unlock(tty);