linux-kernel - [PATCH v5 1/2] usb: dwc2: host: Add missing spinlock in dwc2_hcd_reset

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Date:	Fri, 20 Nov 2015 09:06:27 -0800
From:	Douglas Anderson <dianders@...omium.org>
To:	John Youn <John.Youn@...opsys.com>, balbi@...com
Cc:	Yunzhi Li <lyz@...k-chips.com>,
	Heiko Stübner <heiko@...ech.de>,
	linux-rockchip@...ts.infradead.org,
	Julius Werner <jwerner@...omium.org>,
	gregory.herrero@...el.com, yousaf.kaukab@...el.com,
	dinguyen@...nsource.altera.com,
	Douglas Anderson <dianders@...omium.org>,
	johnyoun@...opsys.com, gregkh@...uxfoundation.org,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v5 1/2] usb: dwc2: host: Add missing spinlock in dwc2_hcd_reset_func()

The dwc2_hcd_reset_func() function is only ever called directly by a
delayed work function.  As such no locks are already held when the
function is called.

Doing a read-modify-write of CPU registers and setting fields in the
main hsotg data structure is a bad idea without locks.  Let's add
locks.

The bug was found by code inspection only.  It turns out that the
dwc2_hcd_reset_func() is only ever called today if the
"host_support_fs_ls_low_power" parameter is enabled and no code in
mainline enables that parameter.  Thus no known issues in mainline are
fixed by this patch, but it's still probably wise to fix the function.

Signed-off-by: Douglas Anderson <dianders@...omium.org>
---
Changes in v5:
- New for v5 of the series

 drivers/usb/dwc2/hcd.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c
index 42b6c5127618..e8924cecc83a 100644
--- a/drivers/usb/dwc2/hcd.c
+++ b/drivers/usb/dwc2/hcd.c
@@ -2357,13 +2357,19 @@ static void dwc2_hcd_reset_func(struct work_struct *work)
 {
 	struct dwc2_hsotg *hsotg = container_of(work, struct dwc2_hsotg,
 						reset_work.work);
+	unsigned long flags;
 	u32 hprt0;
 
 	dev_dbg(hsotg->dev, "USB RESET function called\n");
+
+	spin_lock_irqsave(&hsotg->lock, flags);
+
 	hprt0 = dwc2_read_hprt0(hsotg);
 	hprt0 &= ~HPRT0_RST;
 	dwc2_writel(hprt0, hsotg->regs + HPRT0);
 	hsotg->flags.b.port_reset_change = 1;
+
+	spin_unlock_irqrestore(&hsotg->lock, flags);
 }
 
 /*
-- 
2.6.0.rc2.230.g3dd15c0

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