On 09-02-23 01:51 am, Alan Stern wrote:
On Wed, Feb 08, 2023 at 09:15:54PM +0530, Prashanth K wrote:
On 08-02-23 08:24 pm, Greg Kroah-Hartman wrote:
On Wed, Feb 08, 2023 at 07:24:47PM +0530, Prashanth K wrote:
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
gserial->port and thus causing null pointer dereference.Add
a null pointer check to prevent this.
Fixes: aba3a8d01d62 (" usb: gadget: u_serial: add suspend resume callbacks")
Nit, and our tools will complain, no " " before the "usb:" string here,
right?
Will fix it in next patch.
Signed-off-by: Prashanth K <quic_prashk@xxxxxxxxxxx>
---
drivers/usb/gadget/function/u_serial.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
index 840626e..98be2b8 100644
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -1428,6 +1428,9 @@ void gserial_resume(struct gserial *gser)
struct gs_port *port = gser->ioport;
unsigned long flags;
+ if (!port)
+ return;
+
What prevents port from going to NULL right after this check?
In our case we got a null pointer de-reference while performing USB
compliance tests, as the gser->port was null. Because in gserial_resume,
spinlock_irq_save(&port->port_lock) accesses a null-pointer as port was
already marked null by gserial_disconnect.
And after gserial_resume acquires the spinlock, gserial_disconnect cant mark
it null until the spinlock is released. We need to check if the port->lock
is valid before accessing it, otherwise it can lead to the above mentioned
scenario
What happens if gserial_disconnect sets gser->port to NULL immediately
after your new check occurs, but before
spinlock_irq_save(&port->port_lock) gets called?
You may need to add a static spinlock to prevent this from happening.
Alan Stern
In that case i guess we have to make port_lock a global variable and
take it out of gs_port structure.
+ static DEFINE_SPINLOCK(port_lock);
struct gs_port {
struct tty_port port;
- spinlock_t port_lock;
This will require us to change all the spinlock(port->port_lock) used in
u_serial.c, what do you suggest?
