On 8/6/21 12:13 PM, Anirudh Rayabharam wrote:
In vhci_device_unlink_cleanup(), the URBs for unsent unlink requests are
not given back. This sometimes causes usb_kill_urb to wait indefinitely
for that urb to be given back. syzbot has reported a hung task issue [1]
for this.
To fix this, give back the urbs corresponding to unsent unlink requests
(unlink_tx list) similar to how urbs corresponding to unanswered unlink
requests (unlink_rx list) are given back. Since the code is almost the
same, extract it into a new function and call it for both unlink_rx and
unlink_tx lists.
Let's not do the refactor - let's first fix the problem and then the refactor.
[1]: https://syzkaller.appspot.com/bug?id=08f12df95ae7da69814e64eb5515d5a85ed06b76
Reported-by: syzbot+74d6ef051d3d2eacf428@xxxxxxxxxxxxxxxxxxxxxxxxx
Tested-by: syzbot+74d6ef051d3d2eacf428@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Anirudh Rayabharam <mail@xxxxxxxxxxxxx>
---
Changes in v2:
Use WARN_ON() instead of BUG() when unlink_list is neither unlink_tx nor
unlink_rx.
v1: https://lore.kernel.org/lkml/20210806164015.25263-1-mail@xxxxxxxxxxxxx/
---
drivers/usb/usbip/vhci_hcd.c | 45 +++++++++++++++++++++++++-----------
1 file changed, 32 insertions(+), 13 deletions(-)
diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
index 4ba6bcdaa8e9..67e638f4c455 100644
--- a/drivers/usb/usbip/vhci_hcd.c
+++ b/drivers/usb/usbip/vhci_hcd.c
@@ -945,7 +945,8 @@ static int vhci_urb_dequeue(struct usb_hcd *hcd, struct urb *urb, int status)
return 0;
}
-static void vhci_device_unlink_cleanup(struct vhci_device *vdev)
+static void __vhci_cleanup_unlink_list(struct vhci_device *vdev,
+ struct list_head *unlink_list)
{
struct vhci_hcd *vhci_hcd = vdev_to_vhci_hcd(vdev);
struct usb_hcd *hcd = vhci_hcd_to_hcd(vhci_hcd);
@@ -953,23 +954,23 @@ static void vhci_device_unlink_cleanup(struct vhci_device *vdev)
struct vhci_unlink *unlink, *tmp;
unsigned long flags;
+ if (WARN(unlink_list != &vdev->unlink_tx
+ && unlink_list != &vdev->unlink_rx,
+ "Invalid list passed to __vhci_cleanup_unlink_list\n"))
+ return;
+
With this change, this will be only place unlink_rx is used without
vdev->priv_lock hold? Please explain why this is safe.
spin_lock_irqsave(&vhci->lock, flags);
spin_lock(&vdev->priv_lock);
- list_for_each_entry_safe(unlink, tmp, &vdev->unlink_tx, list) {
- pr_info("unlink cleanup tx %lu\n", unlink->unlink_seqnum);
- list_del(&unlink->list);
- kfree(unlink);
- }
-
- while (!list_empty(&vdev->unlink_rx)) {
+ list_for_each_entry_safe(unlink, tmp, unlink_list, list) {
struct urb *urb;
- unlink = list_first_entry(&vdev->unlink_rx, struct vhci_unlink,
- list);
-
- /* give back URB of unanswered unlink request */
- pr_info("unlink cleanup rx %lu\n", unlink->unlink_seqnum);
+ if (unlink_list == &vdev->unlink_tx)
+ pr_info("unlink cleanup tx %lu\n",
+ unlink->unlink_seqnum);
+ else
+ pr_info("unlink cleanup rx %lu\n",
+ unlink->unlink_seqnum);
urb = pickup_urb_and_free_priv(vdev, unlink->unlink_seqnum);
if (!urb) {
@@ -1001,6 +1002,24 @@ static void vhci_device_unlink_cleanup(struct vhci_device *vdev)
spin_unlock_irqrestore(&vhci->lock, flags);
}
+static inline void vhci_cleanup_unlink_tx(struct vhci_device *vdev)
+{
+ __vhci_cleanup_unlink_list(vdev, &vdev->unlink_tx);
With this change, this will be only place unlink_rx is used without
vdev->priv_lock hold? Please explain why this is safe.
+}
+
Is there a need for this layer?
+static inline void vhci_cleanup_unlink_rx(struct vhci_device *vdev)
+{
+ __vhci_cleanup_unlink_list(vdev, &vdev->unlink_rx);
With this change, this will be only place unlink_rx is used without
vdev->priv_lock hold? Please explain why this is safe.
+}
+
Is there a need for this layer?
+static void vhci_device_unlink_cleanup(struct vhci_device *vdev)
+{
+ /* give back URBs of unsent unlink requests */
+ vhci_cleanup_unlink_tx(vdev);
+ /* give back URBs of unanswered unlink requests */
+ vhci_cleanup_unlink_rx(vdev);
+}
+
/*
* The important thing is that only one context begins cleanup.
* This is why error handling and cleanup become simple.
thanks,
-- Shuah
