usb: gadget: u_serial: Add null pointer check in gserial_suspend

[ Upstream commit 2f6ecb89fe8feb2b60a53325b0eeb9866d88909a ]

Consider a case where gserial_disconnect has already cleared
gser->ioport. And if gserial_suspend gets called afterwards,
it will lead to accessing of gser->ioport and thus causing
null pointer dereference.

Avoid this by adding a null pointer check. Added a static
spinlock to prevent gser->ioport from becoming null after
the newly added null pointer check.

Fixes: aba3a8d01d62 ("usb: gadget: u_serial: add suspend resume callbacks")
Signed-off-by: Prashanth K <quic_prashk@quicinc.com>
Link: https://lore.kernel.org/r/1683278317-11774-1-git-send-email-quic_prashk@quicinc.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
index db6fd02..ea2c5b6 100644 (file)
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -1419,10 +1419,19 @@ EXPORT_SYMBOL_GPL(gserial_disconnect);
 
 void gserial_suspend(struct gserial *gser)
 {
-       struct gs_port  *port = gser->ioport;
+       struct gs_port  *port;
        unsigned long   flags;
 
-       spin_lock_irqsave(&port->port_lock, flags);
+       spin_lock_irqsave(&serial_port_lock, flags);
+       port = gser->ioport;
+
+       if (!port) {
+               spin_unlock_irqrestore(&serial_port_lock, flags);
+               return;
+       }
+
+       spin_lock(&port->port_lock);
+       spin_unlock(&serial_port_lock);
        port->suspended = true;
        spin_unlock_irqrestore(&port->port_lock, flags);
 }