Patch "usb: gadget: u_serial: Add null pointer check in gserial_suspend" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

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

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     usb-gadget-u_serial-add-null-pointer-check-in-gseria.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit f4ee10efa42ca0eec08e637e5f4b4673ef81d2b0
Author: Prashanth K <quic_prashk@xxxxxxxxxxx>
Date:   Fri May 5 14:48:37 2023 +0530

    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@xxxxxxxxxxx>
    Link: https://lore.kernel.org/r/1683278317-11774-1-git-send-email-quic_prashk@xxxxxxxxxxx
    Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
index 116d2e15e9b22..a8d1e8b192c55 100644
--- 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);
 }