Consider a case where gserial_disconnect has already cleared
gser->ioport. And if a wakeup interrupt triggers afterwards,
gserial_resume gets called, which will lead to accessing of
gser->ioport and thus causing null pointer dereference.Add
a null pointer check to prevent this.
Added a static spinlock to prevent gser->ioport from becoming
null after the newly added check.
Fixes: aba3a8d01d62 ("usb: gadget: u_serial: add suspend resume callbacks")
Signed-off-by: Prashanth K <quic_prashk@xxxxxxxxxxx>
---
v4: Added short comment about serial_port_lock.
drivers/usb/gadget/function/u_serial.c | 27 +++++++++++++++++++++++----
1 file changed, 23 insertions(+), 4 deletions(-)
diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
index 840626e..3a6adf2 100644
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -82,6 +82,13 @@
#define WRITE_BUF_SIZE 8192 /* TX only */
#define GS_CONSOLE_BUF_SIZE 8192
+/*
+ * Since all the spinlocks used in this driver is part of struct gs_port (port_lock).
+ * Added a new static spinlock to prevent race conditions where gs_port is dereferenced
+ * after marking as null.
+ */
+static DEFINE_SPINLOCK(serial_port_lock);
+
/* console info */
struct gs_console {
struct console console;
@@ -1375,8 +1382,10 @@ void gserial_disconnect(struct gserial *gser)
if (!port)
return;
+ spin_lock_irqsave(&serial_port_lock, flags);
+
/* tell the TTY glue not to do I/O here any more */
- spin_lock_irqsave(&port->port_lock, flags);
+ spin_lock(&port->port_lock);
gs_console_disconnect(port);
@@ -1391,7 +1400,8 @@ void gserial_disconnect(struct gserial *gser)
tty_hangup(port->port.tty);
}
port->suspended = false;
- spin_unlock_irqrestore(&port->port_lock, flags);
+ spin_unlock(&port->port_lock);
+ spin_unlock_irqrestore(&serial_port_lock, flags);
/* disable endpoints, aborting down any active I/O */
usb_ep_disable(gser->out);
@@ -1425,10 +1435,19 @@ EXPORT_SYMBOL_GPL(gserial_suspend);
void gserial_resume(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 = false;
if (!port->start_delayed) {
spin_unlock_irqrestore(&port->port_lock, flags);
--
2.7.4
