This is a note to let you know that I've just added the patch titled

xhci: Fix use-after-free regression in xhci clear hub TT

to my usb git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git in the usb-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From 18b74067ac78a2dea65783314c13df98a53d071c Mon Sep 17 00:00:00 2001

From: Mathias Nyman mathias.nyman@linux.intel.com Date: Fri, 25 Oct 2019 17:30:27 +0300 Subject: xhci: Fix use-after-free regression in xhci clear hub TT implementation

commit ef513be0a905 ("usb: xhci: Add Clear_TT_Buffer") schedules work to clear TT buffer, but causes a use-after-free regression at the same time

Make sure hub_tt_work finishes before endpoint is disabled, otherwise the work will dereference already freed endpoint and device related pointers.

This was triggered when usb core failed to read the configuration descriptor of a FS/LS device during enumeration. xhci driver queued clear_tt_work while usb core freed and reallocated a new device for the next enumeration attempt.

EHCI driver implents ehci_endpoint_disable() that makes sure clear_tt_work has finished before it returns, but xhci lacks this support. usb core will call hcd->driver->endpoint_disable() callback before disabling endpoints, so we want this in xhci as well.

The added xhci_endpoint_disable() is based on ehci_endpoint_disable()

Fixes: ef513be0a905 ("usb: xhci: Add Clear_TT_Buffer") Cc: stable@vger.kernel.org # v5.3 Reported-by: Johan Hovold johan@kernel.org Suggested-by: Johan Hovold johan@kernel.org Reviewed-by: Johan Hovold johan@kernel.org Tested-by: Johan Hovold johan@kernel.org Signed-off-by: Mathias Nyman mathias.nyman@linux.intel.com Link: https://lore.kernel.org/r/1572013829-14044-2-git-send-email-mathias.nyman@li... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/host/xhci.c | 54 ++++++++++++++++++++++++++++++++++------- 1 file changed, 45 insertions(+), 9 deletions(-)

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c index 517ec3206f6e..6c17e3fe181a 100644 --- a/drivers/usb/host/xhci.c +++ b/drivers/usb/host/xhci.c @@ -3071,6 +3071,48 @@ void xhci_cleanup_stalled_ring(struct xhci_hcd *xhci, unsigned int ep_index, } }

+static void xhci_endpoint_disable(struct usb_hcd *hcd, + struct usb_host_endpoint *host_ep) +{ + struct xhci_hcd *xhci; + struct xhci_virt_device *vdev; + struct xhci_virt_ep *ep; + struct usb_device *udev; + unsigned long flags; + unsigned int ep_index; + + xhci = hcd_to_xhci(hcd); +rescan: + spin_lock_irqsave(&xhci->lock, flags); + + udev = (struct usb_device *)host_ep->hcpriv; + if (!udev || !udev->slot_id) + goto done; + + vdev = xhci->devs[udev->slot_id]; + if (!vdev) + goto done; + + ep_index = xhci_get_endpoint_index(&host_ep->desc); + ep = &vdev->eps[ep_index]; + if (!ep) + goto done; + + /* wait for hub_tt_work to finish clearing hub TT */ + if (ep->ep_state & EP_CLEARING_TT) { + spin_unlock_irqrestore(&xhci->lock, flags); + schedule_timeout_uninterruptible(1); + goto rescan; + } + + if (ep->ep_state) + xhci_dbg(xhci, "endpoint disable with ep_state 0x%x\n", + ep->ep_state); +done: + host_ep->hcpriv = NULL; + spin_unlock_irqrestore(&xhci->lock, flags); +} + /* * Called after usb core issues a clear halt control message. * The host side of the halt should already be cleared by a reset endpoint @@ -5238,20 +5280,13 @@ static void xhci_clear_tt_buffer_complete(struct usb_hcd *hcd, unsigned int ep_index; unsigned long flags;

- /* - * udev might be NULL if tt buffer is cleared during a failed device - * enumeration due to a halted control endpoint. Usb core might - * have allocated a new udev for the next enumeration attempt. - */ - xhci = hcd_to_xhci(hcd); + + spin_lock_irqsave(&xhci->lock, flags); udev = (struct usb_device *)ep->hcpriv; - if (!udev) - return; slot_id = udev->slot_id; ep_index = xhci_get_endpoint_index(&ep->desc);

- spin_lock_irqsave(&xhci->lock, flags); xhci->devs[slot_id]->eps[ep_index].ep_state &= ~EP_CLEARING_TT; xhci_ring_doorbell_for_active_rings(xhci, slot_id, ep_index); spin_unlock_irqrestore(&xhci->lock, flags); @@ -5288,6 +5323,7 @@ static const struct hc_driver xhci_hc_driver = { .free_streams = xhci_free_streams, .add_endpoint = xhci_add_endpoint, .drop_endpoint = xhci_drop_endpoint, + .endpoint_disable = xhci_endpoint_disable, .endpoint_reset = xhci_endpoint_reset, .check_bandwidth = xhci_check_bandwidth, .reset_bandwidth = xhci_reset_bandwidth,