From: Vincent Palatin Date: Thu, 1 Nov 2012 18:05:28 +0000 (-0700) Subject: USB: ohci-exynos: initialize registers pointer earlier X-Git-Tag: firefly_0821_release~3680^2~1517^2~66 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=57465109ce6c62e57b98788496c823c2067253c0;p=firefly-linux-kernel-4.4.55.git USB: ohci-exynos: initialize registers pointer earlier In the former code, we have a race condition between the first interrupt and the regs field initilization in the usb_hcd structure. If the OHCI irq fires before hcd->regs is set, we are getting a null pointer dereference in ohci_irq. When calling usb_add_hcd(), it first executes the reset() callback, then enables the ohci interrupt, and finally executes the start() callback. So moving the ohci_init() call which actually initializes the reg field from start() to reset() should remove the race. Tested by enabling the external HSIC hub in the bootloader on an exynos5 machine and booting. With the former code, this triggers an early interrupt about 50% of the boots and a subsequent kernel panic in ohci_irq when trying to access the registers. Cc: Olof Johansson Cc: Doug Anderson Cc: Arjun.K.V Cc: Vikas Sajjan Cc: Abhilash Kesavan Signed-off-by: Vincent Palatin Acked-by: Alan Stern Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/usb/host/ohci-exynos.c b/drivers/usb/host/ohci-exynos.c index 2f303295b428..6a30fc5bec93 100644 --- a/drivers/usb/host/ohci-exynos.c +++ b/drivers/usb/host/ohci-exynos.c @@ -23,6 +23,11 @@ struct exynos_ohci_hcd { struct clk *clk; }; +static int ohci_exynos_reset(struct usb_hcd *hcd) +{ + return ohci_init(hcd_to_ohci(hcd)); +} + static int ohci_exynos_start(struct usb_hcd *hcd) { struct ohci_hcd *ohci = hcd_to_ohci(hcd); @@ -30,10 +35,6 @@ static int ohci_exynos_start(struct usb_hcd *hcd) ohci_dbg(ohci, "ohci_exynos_start, ohci:%p", ohci); - ret = ohci_init(ohci); - if (ret < 0) - return ret; - ret = ohci_run(ohci); if (ret < 0) { dev_err(hcd->self.controller, "can't start %s\n", @@ -53,6 +54,7 @@ static const struct hc_driver exynos_ohci_hc_driver = { .irq = ohci_irq, .flags = HCD_MEMORY|HCD_USB11, + .reset = ohci_exynos_reset, .start = ohci_exynos_start, .stop = ohci_stop, .shutdown = ohci_shutdown,