[PATCH 5.10 18/19] usb: gadget: u_serial: Add null pointer check in gserial_resume

Greg Kroah-Hartman
2023-03-01T18:10:22Z

From: Prashanth K <quic_prashk@quicinc.com>

commit 5ec63fdbca604568890c577753c6f66c5b3ef0b5 upstream.

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")
Cc: stable <stable@kernel.org>
Signed-off-by: Prashanth K <quic_prashk@quicinc.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/1676309438-14922-1-git-send-email-quic_prashk@quicinc.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/gadget/function/u_serial.c | 23 +++++++++++++++++++----
1 file changed, 19 insertions(+), 4 deletions(-)

--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -81,6 +81,9 @@
#define WRITE_BUF_SIZE 8192 /* TX only */
#define GS_CONSOLE_BUF_SIZE 8192

+/* Prevents race conditions while accessing gser->ioport */
+static DEFINE_SPINLOCK(serial_port_lock);
+
/* console info */
struct gs_console {
struct console console;
@@ -1376,8 +1379,10 @@ void gserial_disconnect(struct gserial *
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);

@@ -1392,7 +1397,8 @@ void gserial_disconnect(struct gserial *
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);
@@ -1426,10 +1432,19 @@ 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);