Re: [RFT PATCH] xhci: Fix null pointer dereference in resume if xhci has only one roothub

From: Matthias Kaehlcke <mka@chromium.org>
To: Mathias Nyman <mathias.nyman@linux.intel.com>
Cc: hkallweit1@gmail.com, gregkh@linuxfoundation.org,
	stern@rowland.harvard.edu, linux-usb@vger.kernel.org,
	quic_jackp@quicinc.com, tunguyen@apm.com,
	linux-amlogic@lists.infradead.org
Subject: Re: [RFT PATCH] xhci: Fix null pointer dereference in resume if xhci has only one roothub
Date: Thu, 9 Jun 2022 08:41:36 -0700	[thread overview]
Message-ID: <YqIUsP437G8g75YS@google.com> (raw)
In-Reply-To: <20220609120336.831533-1-mathias.nyman@linux.intel.com>

On Thu, Jun 09, 2022 at 03:03:36PM +0300, Mathias Nyman wrote:
> In the re-init path xhci_resume() passes 'hcd->primary_hcd' to hci_init(),
> however this field isn't initialized by __usb_create_hcd() for a HCD
> without secondary controller.
> 
> xhci_resume() is called once per xHC device, not per hcd, so the extra
> checking for primary hcd can be removed.
> 
> Fixes: e0fe986972f5 ("usb: host: xhci-plat: prepare operation w/o shared hcd")
> Reported-by: Matthias Kaehlcke <mka@chromium.org>
> Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
> ---
>  drivers/usb/host/xhci.c | 15 +++++----------
>  1 file changed, 5 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index f0ab63138016..9ac56e9ffc64 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/drivers/usb/host/xhci.c
> @@ -1107,7 +1107,6 @@ int xhci_resume(struct xhci_hcd *xhci, bool hibernated)
>  {
>  	u32			command, temp = 0;
>  	struct usb_hcd		*hcd = xhci_to_hcd(xhci);
> -	struct usb_hcd		*secondary_hcd;
>  	int			retval = 0;
>  	bool			comp_timer_running = false;
>  	bool			pending_portevent = false;
> @@ -1214,23 +1213,19 @@ int xhci_resume(struct xhci_hcd *xhci, bool hibernated)
>  		 * first with the primary HCD, and then with the secondary HCD.
>  		 * If we don't do the same, the host will never be started.
>  		 */
> -		if (!usb_hcd_is_primary_hcd(hcd))
> -			secondary_hcd = hcd;
> -		else
> -			secondary_hcd = xhci->shared_hcd;
> -
>  		xhci_dbg(xhci, "Initialize the xhci_hcd\n");
> -		retval = xhci_init(hcd->primary_hcd);
> +		retval = xhci_init(hcd);
>  		if (retval)
>  			return retval;
>  		comp_timer_running = true;
>  
>  		xhci_dbg(xhci, "Start the primary HCD\n");

Is the log still correct? IIUC this now isn't necessarily the primary HCD.

> -		retval = xhci_run(hcd->primary_hcd);
> -		if (!retval && secondary_hcd) {
> +		retval = xhci_run(hcd);
> +		if (!retval && xhci->shared_hcd) {
>  			xhci_dbg(xhci, "Start the secondary HCD\n");

ditto

> -			retval = xhci_run(secondary_hcd);
> +			retval = xhci_run(xhci->shared_hcd);
>  		}
> +
>  		hcd->state = HC_STATE_SUSPENDED;
>  		if (xhci->shared_hcd)
>  			xhci->shared_hcd->state = HC_STATE_SUSPENDED;

Tested-by: Matthias Kaehlcke <mka@chromium.org>

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