This reverts commit ffd603f214237e250271162a5b325c6199a65382.
Commit ffd603f21423 ("usb: gadget: u_serial: Add null pointer check in gs_start_io") adds null pointer checks at the beginning of the gs_start_io() function to prevent a null pointer dereference. However, these checks are redundant because the function's comment already requires callers to hold the port_lock and ensure port.tty and port_usb are not null. All existing callers already follow these rules.
The true cause of the null pointer dereference is a race condition. When gs_start_io() calls either gs_start_rx() or gs_start_tx(), the port_lock is temporarily released for usb_ep_queue(). This allows port.tty and port_usb to be cleared.
Cc: stable@vger.kernel.org Fixes: ffd603f21423 ("usb: gadget: u_serial: Add null pointer check in gs_start_io") Signed-off-by: Kuen-Han Tsai khtsai@google.com --- drivers/usb/gadget/function/u_serial.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-)
diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c index ab544f6824be..c043bdc30d8a 100644 --- a/drivers/usb/gadget/function/u_serial.c +++ b/drivers/usb/gadget/function/u_serial.c @@ -544,20 +544,16 @@ static int gs_alloc_requests(struct usb_ep *ep, struct list_head *head, static int gs_start_io(struct gs_port *port) { struct list_head *head = &port->read_pool; - struct usb_ep *ep; + struct usb_ep *ep = port->port_usb->out; int status; unsigned started;
- if (!port->port_usb || !port->port.tty) - return -EIO; - /* Allocate RX and TX I/O buffers. We can't easily do this much * earlier (with GFP_KERNEL) because the requests are coupled to * endpoints, as are the packet sizes we'll be using. Different * configurations may use different endpoints with a given port; * and high speed vs full speed changes packet sizes too. */ - ep = port->port_usb->out; status = gs_alloc_requests(ep, head, gs_read_complete, &port->read_allocated); if (status)