usb: dwc2: host: Avoid use of chan->qh after qh freed

When poking around with USB devices with slub_debug enabled, I found
another obvious use after free.  Turns out that in dwc2_hc_n_intr() I
was in a state when the contents of chan->qh was filled with 0x6b,
indicating that chan->qh was freed but chan still had a reference to
it.

Let's make sure that whenever we free qh we also make sure we remove a
reference from its channel.

The bug fixed here doesn't appear to be new--I believe I just got lucky
and happened to see it while stress testing.

Acked-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>

2 files changed, 20 insertions, 0 deletions

diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c
index bc4bdbc1534e..e2d2e9be366e 100644
--- a/drivers/usb/dwc2/hcd.c
+++ b/drivers/usb/dwc2/hcd.c
@@ -164,6 +164,9 @@ static void dwc2_qh_list_free(struct dwc2_hsotg *hsotg,
                                          qtd_list_entry)
                         dwc2_hcd_qtd_unlink_and_free(hsotg, qtd, qh);
 
+                if (qh->channel && qh->channel->qh == qh)
+                        qh->channel->qh = NULL;
+
                 spin_unlock_irqrestore(&hsotg->lock, flags);
                 dwc2_hcd_qh_free(hsotg, qh);
                 spin_lock_irqsave(&hsotg->lock, flags);
@@ -554,7 +557,12 @@ static int dwc2_hcd_endpoint_disable(struct dwc2_hsotg *hsotg,
                 dwc2_hcd_qtd_unlink_and_free(hsotg, qtd, qh);
 
         ep->hcpriv = NULL;
+
+        if (qh->channel && qh->channel->qh == qh)
+                qh->channel->qh = NULL;
+
         spin_unlock_irqrestore(&hsotg->lock, flags);
+
         dwc2_hcd_qh_free(hsotg, qh);
 
         return 0;
@@ -2782,6 +2790,8 @@ static int _dwc2_hcd_urb_enqueue(struct usb_hcd *hcd, struct urb *urb,
 fail3:
         dwc2_urb->priv = NULL;
         usb_hcd_unlink_urb_from_ep(hcd, urb);
+        if (qh_allocated && qh->channel && qh->channel->qh == qh)
+                qh->channel->qh = NULL;
 fail2:
         spin_unlock_irqrestore(&hsotg->lock, flags);
         urb->hcpriv = NULL;
diff --git a/drivers/usb/dwc2/hcd_intr.c b/drivers/usb/dwc2/hcd_intr.c
index 4270f6c719c6..0d0fd2a7f1f9 100644
--- a/drivers/usb/dwc2/hcd_intr.c
+++ b/drivers/usb/dwc2/hcd_intr.c
@@ -1943,6 +1943,16 @@ static void dwc2_hc_n_intr(struct dwc2_hsotg *hsotg, int chnum)
         }
 
         dwc2_writel(hcint, hsotg->regs + HCINT(chnum));
+
+        /*
+         * If we got an interrupt after someone called
+         * dwc2_hcd_endpoint_disable() we don't want to crash below
+         */
+        if (!chan->qh) {
+                dev_warn(hsotg->dev, "Interrupt on disabled channel\n");
+                return;
+        }
+
         chan->hcint = hcint;
         hcint &= hcintmsk;