@@ -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)
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. Fixes: ffd603f21423 ("usb: gadget: u_serial: Add null pointer check in gs_start_io") Signed-off-by: Kuen-Han Tsai <khtsai@google.com> --- v2: - Remove Cc: stable --- drivers/usb/gadget/function/u_serial.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) -- 2.50.0.rc2.692.g299adb8693-goog