When a driver tries to cancel an URB, and the host controller is dying,
xhci_urb_dequeue will giveback the URB without removing the xhci_tds
that comprise that URB from the td_list or the cancelled_td_list. This
can cause a race condition between the driver calling URB dequeue and
the stop endpoint command watchdog timer.
If the timer fires on a dying host, and a driver attempts to resubmit
while the watchdog timer has dropped the xhci->lock to giveback a
cancelled URB, URBs may be given back by the xhci_urb_dequeue() function.
At that point, the URB's priv pointer will be freed and set to NULL, but
the TDs will remain on the td_list. This will cause an oops in
xhci_giveback_urb_in_irq() when the watchdog timer attempts to loop
through the endpoints' td_lists, giving back killed URBs.
Make sure that xhci_urb_dequeue() removes TDs from the TD lists and
canceled TD lists before it gives back the URB.
This patch should be backported to kernels as old as 2.6.36.
Signed-off-by: Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx>
Cc: Andiry Xu <andiry.xu@xxxxxxx>
Cc: stable@xxxxxxxxxx
---
drivers/usb/host/xhci-ring.c | 16 ++++++++--------
drivers/usb/host/xhci.c | 7 +++++++
2 files changed, 15 insertions(+), 8 deletions(-)
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index f72149b..b2d654b 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -741,7 +741,7 @@ remove_finished_td:
* so remove it from the endpoint ring's TD list. Keep it in
* the cancelled TD list for URB completion later.
*/
- list_del(&cur_td->td_list);
+ list_del_init(&cur_td->td_list);
}
last_unlinked_td = cur_td;
xhci_stop_watchdog_timer_in_irq(xhci, ep);
@@ -769,7 +769,7 @@ remove_finished_td:
do {
cur_td = list_entry(ep->cancelled_td_list.next,
struct xhci_td, cancelled_td_list);
- list_del(&cur_td->cancelled_td_list);
+ list_del_init(&cur_td->cancelled_td_list);
/* Clean up the cancelled URB */
/* Doesn't matter what we pass for status, since the core will
@@ -877,9 +877,9 @@ void xhci_stop_endpoint_command_watchdog(unsigned long arg)
cur_td = list_first_entry(&ring->td_list,
struct xhci_td,
td_list);
- list_del(&cur_td->td_list);
+ list_del_init(&cur_td->td_list);
if (!list_empty(&cur_td->cancelled_td_list))
- list_del(&cur_td->cancelled_td_list);
+ list_del_init(&cur_td->cancelled_td_list);
xhci_giveback_urb_in_irq(xhci, cur_td,
-ESHUTDOWN, "killed");
}
@@ -888,7 +888,7 @@ void xhci_stop_endpoint_command_watchdog(unsigned long arg)
&temp_ep->cancelled_td_list,
struct xhci_td,
cancelled_td_list);
- list_del(&cur_td->cancelled_td_list);
+ list_del_init(&cur_td->cancelled_td_list);
xhci_giveback_urb_in_irq(xhci, cur_td,
-ESHUTDOWN, "killed");
}
@@ -1580,10 +1580,10 @@ td_cleanup:
else
*status = 0;
}
- list_del(&td->td_list);
+ list_del_init(&td->td_list);
/* Was this TD slated to be cancelled but completed anyway? */
if (!list_empty(&td->cancelled_td_list))
- list_del(&td->cancelled_td_list);
+ list_del_init(&td->cancelled_td_list);
urb_priv->td_cnt++;
/* Giveback the urb when all the tds are completed */
@@ -3362,7 +3362,7 @@ cleanup:
/* Clean up a partially enqueued isoc transfer. */
for (i--; i >= 0; i--)
- list_del(&urb_priv->td[i]->td_list);
+ list_del_init(&urb_priv->td[i]->td_list);
/* Use the first TD as a temporary variable to turn the TDs we've queued
* into No-ops with a software-owned cycle bit. That way the hardware
diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 8e84acf..3a0f695 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -1252,6 +1252,13 @@ int xhci_urb_dequeue(struct usb_hcd *hcd, struct urb *urb, int status)
if (temp == 0xffffffff || (xhci->xhc_state & XHCI_STATE_HALTED)) {
xhci_dbg(xhci, "HW died, freeing TD.\n");
urb_priv = urb->hcpriv;
+ for (i = urb_priv->td_cnt; i < urb_priv->length; i++) {
+ td = urb_priv->td[i];
+ if (!list_empty(&td->td_list))
+ list_del_init(&td->td_list);
+ if (!list_empty(&td->cancelled_td_list))
+ list_del_init(&td->cancelled_td_list);
+ }
usb_hcd_unlink_urb_from_ep(hcd, urb);
spin_unlock_irqrestore(&xhci->lock, flags);
--
1.7.4.1
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
