diff options
| author | Kuen-Han Tsai <khtsai@google.com> | 2025-06-17 13:07:12 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-06-19 12:41:13 +0200 |
| commit | c529c3730bd09115684644e26bf01ecbd7e2c2c9 (patch) | |
| tree | e295a95e34ef0c755b1aa4a640daaa918e8b0f52 | |
| parent | f6c7bc4a6823a0a959f40866a1efe99bd03c2c5b (diff) | |
usb: gadget: u_serial: Fix race condition in TTY wakeup
A race condition occurs when gs_start_io() calls either gs_start_rx() or
gs_start_tx(), as those functions briefly drop the port_lock for
usb_ep_queue(). This allows gs_close() and gserial_disconnect() to clear
port.tty and port_usb, respectively.
Use the null-safe TTY Port helper function to wake up TTY.
Example
CPU1: CPU2:
gserial_connect() // lock
gs_close() // await lock
gs_start_rx() // unlock
usb_ep_queue()
gs_close() // lock, reset port.tty and unlock
gs_start_rx() // lock
tty_wakeup() // NPE
Fixes: 35f95fd7f234 ("TTY: usb/u_serial, use tty from tty_port")
Cc: stable <stable@kernel.org>
Signed-off-by: Kuen-Han Tsai <khtsai@google.com>
Reviewed-by: Prashanth K <prashanth.k@oss.qualcomm.com>
Link: https://lore.kernel.org/linux-usb/20240116141801.396398-1-khtsai@google.com/
Link: https://lore.kernel.org/r/20250617050844.1848232-2-khtsai@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/usb/gadget/function/u_serial.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c index c043bdc30d8a..540dc5ab96fc 100644 --- a/drivers/usb/gadget/function/u_serial.c +++ b/drivers/usb/gadget/function/u_serial.c @@ -295,8 +295,8 @@ __acquires(&port->port_lock) break; } - if (do_tty_wake && port->port.tty) - tty_wakeup(port->port.tty); + if (do_tty_wake) + tty_port_tty_wakeup(&port->port); return status; } @@ -574,7 +574,7 @@ static int gs_start_io(struct gs_port *port) gs_start_tx(port); /* Unblock any pending writes into our circular buffer, in case * we didn't in gs_start_tx() */ - tty_wakeup(port->port.tty); + tty_port_tty_wakeup(&port->port); } else { /* Free reqs only if we are still connected */ if (port->port_usb) { |