Re: [PATCH] usb: gadget: u_serial: Add null pointer checks after RX/TX submission

[Jiri Slaby <jirislaby@kernel.org>]

On 16. 01. 24, 15:16, Kuen-Han Tsai wrote:
> Commit ffd603f21423 ("usb: gadget: u_serial: Add null pointer check in
> gs_start_io") adds null pointer checks to gs_start_io(), but it doesn't
> fully fix the potential null pointer dereference issue. While
> gserial_connect() calls gs_start_io() with port_lock held, gs_start_rx()
> and gs_start_tx() release the lock during endpoint request submission.
> This creates a window where gs_close() could set port->port_tty to NULL,
> leading to a dereference when the lock is reacquired.
> 
> This patch adds a null pointer check for port->port_tty after RX/TX
> submission, and removes the initial null pointer check in gs_start_io()
> since the caller must hold port_lock and guarantee non-null values for
> port_usb and port_tty.

Or you switch to tty_port refcounting and need not fiddling with this at 
all ;).

thanks,
-- 
js
suse labs