5.4-stable review patch. If anyone has any objections, please let me know.
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From: Kuen-Han Tsai khtsai@google.com
commit c529c3730bd09115684644e26bf01ecbd7e2c2c9 upstream.
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 --- drivers/usb/gadget/function/u_serial.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/drivers/usb/gadget/function/u_serial.c +++ b/drivers/usb/gadget/function/u_serial.c @@ -286,8 +286,8 @@ __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; }
@@ -564,7 +564,7 @@ static int gs_start_io(struct gs_port *p 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) {