Messages in this thread | | | Date | Wed, 29 Nov 2023 16:57:23 +0200 | From | Mathias Nyman <> | Subject | Re: [RFT PATCH 1/2] xhci: Reconfigure endpoint 0 max packet size only during endpoint reset |
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>> + ep_index = xhci_get_endpoint_index(&host_ep->desc); >> + >> + /* >> + * Usb core assumes a max packet value for ep0 on FS devices until the >> + * real value is read from the descriptor. Core resets Ep0 if values >> + * mismatch. Reconfigure the xhci ep0 endpoint context here in that case >> + */ >> + if (usb_endpoint_xfer_control(&host_ep->desc) && ep_index == 0) { >> + udev = container_of(host_ep, struct usb_device, ep0); >> + if (udev->speed == USB_SPEED_FULL) >> + xhci_check_ep0_maxpacket(xhci, xhci->devs[udev->slot_id]); >> + /* Nothing else should be done here for ep0 during ep reset */ >> + return; >> + } >> + > > Could there be a race condition between the xhci_endpoint_reset() and > xhci_free_dev() functions, resulting in the xhci->devs[udev->slot_id] > becoming null? > If so, a null pointer dereference will happen in > xhci_check_ep0_maxpacket() when accessing vdev->out_ctx.
should not race. xhci_free_dev() and xhci_endpoint_reset() for endpoint 0 should only be called by hub driver hub_free_dev() and usb_ep0_reinit() respectively.
Hub driver takes care of concurrency for these
Thanks Mathias
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