linux-kernel - Re: [PATCH 1/2] usb: xhci: fix uninitialized completion when USB3 port got wrong status

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Date:   Mon, 22 Oct 2018 21:23:13 +0800
From:   Aaron Ma <aaron.ma@...onical.com>
To:     Mathias Nyman <mathias.nyman@...ux.intel.com>,
        mathias.nyman@...el.com, gregkh@...uxfoundation.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] usb: xhci: fix uninitialized completion when USB3
 port got wrong status



On 10/22/18 9:12 PM, Mathias Nyman wrote:
> On 21.10.2018 20:08, Aaron Ma wrote:
>> Realtek USB3.0 Card Reader [0bda:0328] reports wrong port status on
>> Cannon lake PCH USB3.1 xHCI [8086:a36d] after resume from S3,
>> after clear port reset it works fine.
>>
>> Since this device is registered on USB3 roothub at boot,
>> when port status reports not superspeed, xhci_get_port_status will call
>> an uninitialized completion in bus_state[0].
>> Kernel will hang because of NULL pointer.
>>
>> Restrict the USB2 resume status check in USB2 roothub to fix hang issue.
>> No harm to initialize USB3 bus_state[0] in case it is called.
>>
>> Signed-off-by: Aaron Ma <aaron.ma@...onical.com>
>> ---
>>   drivers/usb/host/xhci-hub.c  | 2 +-
>>   drivers/usb/host/xhci-mem.c  | 1 +
>>   drivers/usb/host/xhci-ring.c | 2 +-
>>   3 files changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
>> index 7e2a531ba321..d30ca6ceffc9 100644
>> --- a/drivers/usb/host/xhci-hub.c
>> +++ b/drivers/usb/host/xhci-hub.c
>> @@ -876,7 +876,7 @@ static u32 xhci_get_port_status(struct usb_hcd *hcd,
>>               status |= USB_PORT_STAT_SUSPEND;
>>       }
>>       if ((raw_port_status & PORT_PLS_MASK) == XDEV_RESUME &&
>> -        !DEV_SUPERSPEED_ANY(raw_port_status)) {
>> +        !DEV_SUPERSPEED_ANY(raw_port_status) && 1 == hcd_index(hcd)) {
>>           if ((raw_port_status & PORT_RESET) ||
>>                   !(raw_port_status & PORT_PE))
>>               return 0xffffffff;
> 
> Nice catch.
> 
> Maybe use "hcd->speed < HCD_USB3" instead of "1 == hcd_index(hcd)"
> It's easier to understand.
> 
> Turns out this isn't an issue with your Realtek device, it just happens
> to trigger
> a driver issue.
> 
> The original !DEV_SUPERSPEED_ANY() check was not suitable here.
> It checks the port-speed field of portsc register (bits 13:10), which
> are only valid for USB3
> ports if all link training is done and port reached its "enabled" state.
> Otherwise it will return 0, and USB3 ports may be mistaken for USB2 ports.
> 
> Just to make sure, Does your device stay as a USB 3 device, it's never
> enumerated as USB2, right?
> 
> I'm in the middle of refactoring the get_port_status(), it should solve
> this
> as well, but we need your solution stable releases.
> 
> Any chance you to check if the refactored code works with the Realtek
> device?
> I just created a "get_port_status_refactor" branch for it:
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/mnyman/xhci.git
> get_port_status_refactor

Let me try your branch, please wait a moment.

> 
>> diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
>> index b1f27aa38b10..dd2ad50c5289 100644
>> --- a/drivers/usb/host/xhci-mem.c
>> +++ b/drivers/usb/host/xhci-mem.c
>> @@ -2539,6 +2539,7 @@ int xhci_mem_init(struct xhci_hcd *xhci, gfp_t
>> flags)
>>           xhci->bus_state[0].resume_done[i] = 0;
>>           xhci->bus_state[1].resume_done[i] = 0;
>>           /* Only the USB 2.0 completions will ever be used. */
>> +        init_completion(&xhci->bus_state[0].rexit_done[i]);
>>           init_completion(&xhci->bus_state[1].rexit_done[i]);
>>       }
> 
> I don't think we should init the completion unnecessary for USB3 ports.
> 
>>   diff --git a/drivers/usb/host/xhci-ring.c
>> b/drivers/usb/host/xhci-ring.c
>> index f0a99aa0ac58..894d4625b8b9 100644
>> --- a/drivers/usb/host/xhci-ring.c
>> +++ b/drivers/usb/host/xhci-ring.c
>> @@ -1634,7 +1634,7 @@ static void handle_port_status(struct xhci_hcd
>> *xhci,
>>        * RExit to a disconnect state).  If so, let the the driver know
>> it's
>>        * out of the RExit state.
>>        */
>> -    if (!DEV_SUPERSPEED_ANY(portsc) &&
>> +    if (!DEV_SUPERSPEED_ANY(portsc) && 1 == hcd_index(hcd) &&
>>               test_and_clear_bit(hcd_portnum,
>>                   &bus_state->rexit_ports)) {
>>           complete(&bus_state->rexit_done[hcd_portnum]);
>>
> 
> Same here, prefer hcd->speed < HCD_USB3

Yes, I thought about this, bus_state[1/0] are defined to USB 2/3, so I
used "1 == hcd_index(hcd)".

Anyway, I will send V2 as your suggestion.

Thanks,
Aaron

> 
> Thanks
> Mathias