tty_port: handle the nonblocking open of a dead port corner case

Some drivers allow O_NDELAY of a dead port (eg for setserial to work). In that
situation we must not try to raise the carrier.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 5 insertions, 2 deletions

diff --git a/drivers/char/tty_port.c b/drivers/char/tty_port.c
index 2e8552dc5eda..c63f3d33914a 100644
--- a/drivers/char/tty_port.c
+++ b/drivers/char/tty_port.c
@@ -219,8 +219,11 @@ int tty_port_block_til_ready(struct tty_port *port,
 
         /* if non-blocking mode is set we can pass directly to open unless
            the port has just hung up or is in another error state */
-        if ((filp->f_flags & O_NONBLOCK) ||
-                        (tty->flags & (1 << TTY_IO_ERROR))) {
+        if (tty->flags & (1 << TTY_IO_ERROR)) {
+                port->flags |= ASYNC_NORMAL_ACTIVE;
+                return 0;
+        }
+        if (filp->f_flags & O_NONBLOCK) {
                 /* Indicate we are open */
                 if (tty->termios->c_cflag & CBAUD)
                         tty_port_raise_dtr_rts(port);