linux-kernel - [PATCH] xhci-mtk: Fix NULL pointer dereference with xhci_irq() for shared

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Date:   Fri, 17 Jan 2020 15:41:50 +0800
From:   Macpaul Lin <macpaul.lin@...iatek.com>
To:     Mathias Nyman <mathias.nyman@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        <linux-usb@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>
CC:     Mediatek WSD Upstream <wsd_upstream@...iatek.com>,
        Macpaul Lin <macpaul.lin@...iatek.com>,
        Sriharsha Allenki <sallenki@...eaurora.org>
Subject: [PATCH] xhci-mtk: Fix NULL pointer dereference with xhci_irq() for shared_hcd

According to NULL pointer fix: https://tinyurl.com/uqft5ra
xhci: Fix NULL pointer dereference with xhci_irq() for shared_hcd
The similar issue has also been found in QC activities in Mediatek.

Here quote the description from the referenced patch as follows.
"Commit ("f068090426ea xhci: Fix leaking USB3 shared_hcd
at xhci removal") sets xhci_shared_hcd to NULL without
stopping xhci host. This results into a race condition
where shared_hcd (super speed roothub) related interrupts
are being handled with xhci_irq happens when the
xhci_plat_remove is called and shared_hcd is set to NULL.
Fix this by setting the shared_hcd to NULL only after the
controller is halted and no interrupts are generated."

Signed-off-by: Sriharsha Allenki <sallenki@...eaurora.org>
Signed-off-by: Macpaul Lin <macpaul.lin@...iatek.com>
---
 drivers/usb/host/xhci-mtk.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/host/xhci-mtk.c b/drivers/usb/host/xhci-mtk.c
index b18a6baef204..c227c67f5dc5 100644
--- a/drivers/usb/host/xhci-mtk.c
+++ b/drivers/usb/host/xhci-mtk.c
@@ -593,11 +593,11 @@ static int xhci_mtk_remove(struct platform_device *dev)
 	struct usb_hcd  *shared_hcd = xhci->shared_hcd;

 	usb_remove_hcd(shared_hcd);
-	xhci->shared_hcd = NULL;
 	device_init_wakeup(&dev->dev, false);

 	usb_remove_hcd(hcd);
 	usb_put_hcd(shared_hcd);
+	xhci->shared_hcd = NULL;
 	usb_put_hcd(hcd);
 	xhci_mtk_sch_exit(mtk);
 	xhci_mtk_clks_disable(mtk);
-- 
2.18.0