linux-kernel - [PATCH] USB: c67x00: fix use after free in c67x00_giveback

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Date:   Wed,  8 Jul 2020 06:12:43 -0700
From:   trix@...hat.com
To:     jacmet@...site.dk, gregkh@...uxfoundation.org
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Tom Rix <trix@...hat.com>
Subject: [PATCH] USB: c67x00: fix use after free in c67x00_giveback_urb

From: Tom Rix <trix@...hat.com>

clang static analysis flags this error

c67x00-sched.c:489:55: warning: Use of memory after it is freed [unix.Malloc]
        usb_hcd_giveback_urb(c67x00_hcd_to_hcd(c67x00), urb, urbp->status);
                                                             ^~~~~~~~~~~~
Problem happens in this block of code

	c67x00_release_urb(c67x00, urb);
	usb_hcd_unlink_urb_from_ep(c67x00_hcd_to_hcd(c67x00), urb);
	spin_unlock(&c67x00->lock);
	usb_hcd_giveback_urb(c67x00_hcd_to_hcd(c67x00), urb, urbp->status);

In the call to c67x00_release_urb has this freeing of urbp

	urbp = urb->hcpriv;
	urb->hcpriv = NULL;
	list_del(&urbp->hep_node);
	kfree(urbp);

And so urbp is freed before usb_hcd_giveback_urb uses it as its 3rd
parameter.

Since all is required is the status, pass the status directly as is
done in c64x00_urb_dequeue

Fixes: e9b29ffc519b ("USB: add Cypress c67x00 OTG controller HCD driver")

Signed-off-by: Tom Rix <trix@...hat.com>
---
 drivers/usb/c67x00/c67x00-sched.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/c67x00/c67x00-sched.c b/drivers/usb/c67x00/c67x00-sched.c
index ef1e4ecaee99..f7f6229082ca 100644
--- a/drivers/usb/c67x00/c67x00-sched.c
+++ b/drivers/usb/c67x00/c67x00-sched.c
@@ -486,7 +486,7 @@ c67x00_giveback_urb(struct c67x00_hcd *c67x00, struct urb *urb, int status)
 	c67x00_release_urb(c67x00, urb);
 	usb_hcd_unlink_urb_from_ep(c67x00_hcd_to_hcd(c67x00), urb);
 	spin_unlock(&c67x00->lock);
-	usb_hcd_giveback_urb(c67x00_hcd_to_hcd(c67x00), urb, urbp->status);
+	usb_hcd_giveback_urb(c67x00_hcd_to_hcd(c67x00), urb, status);
 	spin_lock(&c67x00->lock);
 }
 
-- 
2.18.1