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>

1 files changed, 10 insertions, 0 deletions

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;