[PATCH v2] usbip: give back URBs for unsent unlink requests during cleanup

[PATCH v2] usbip: give back URBs for unsent unlink requests during cleanup

[Anirudh Rayabharam]

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.

[1]: https://syzkaller.appspot.com/bug?id=08f12df95ae7da69814e64eb5515d5a85ed06b76

Reported-by: syzbot+74d6ef051d3d2eacf428@syzkaller.appspotmail.com
Tested-by: syzbot+74d6ef051d3d2eacf428@syzkaller.appspotmail.com
Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
---

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@anirudhrb.com/

---
 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;
+
 	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);
+}
+
+static inline void vhci_cleanup_unlink_rx(struct vhci_device *vdev)
+{
+	__vhci_cleanup_unlink_list(vdev, &vdev->unlink_rx);
+}
+
+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.
-- 
2.26.2

[PATCH v2] usbip: give back URBs for unsent unlink requests during cleanup

[Anirudh Rayabharam]

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.

[1]: https://syzkaller.appspot.com/bug?id=08f12df95ae7da69814e64eb5515d5a85ed06b76

Reported-by: syzbot+74d6ef051d3d2eacf428@syzkaller.appspotmail.com
Tested-by: syzbot+74d6ef051d3d2eacf428@syzkaller.appspotmail.com
Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
---

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@anirudhrb.com/

---
 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;
+
 	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);
+}
+
+static inline void vhci_cleanup_unlink_rx(struct vhci_device *vdev)
+{
+	__vhci_cleanup_unlink_list(vdev, &vdev->unlink_rx);
+}
+
+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.
-- 
2.26.2

_______________________________________________
Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees

Re: [PATCH v2] usbip: give back URBs for unsent unlink requests during cleanup

[Shuah Khan]

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@syzkaller.appspotmail.com
> Tested-by: syzbot+74d6ef051d3d2eacf428@syzkaller.appspotmail.com
> Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
> ---
> 
> 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@anirudhrb.com/
> 
> ---
>   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

Re: [PATCH v2] usbip: give back URBs for unsent unlink requests during cleanup

[Shuah Khan]

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@syzkaller.appspotmail.com
> Tested-by: syzbot+74d6ef051d3d2eacf428@syzkaller.appspotmail.com
> Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
> ---
> 
> 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@anirudhrb.com/
> 
> ---
>   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
_______________________________________________
Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees

Re: [PATCH v2] usbip: give back URBs for unsent unlink requests during cleanup

[Anirudh Rayabharam]

On Tue, Aug 10, 2021 at 05:25:51PM -0600, Shuah Khan wrote:
> 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.

Sure, I will make it a two patch series where the first one fixes the
problem and the second one does the refactor.

> 
> > [1]: https://syzkaller.appspot.com/bug?id=08f12df95ae7da69814e64eb5515d5a85ed06b76
> > 
> > Reported-by: syzbot+74d6ef051d3d2eacf428@syzkaller.appspotmail.com
> > Tested-by: syzbot+74d6ef051d3d2eacf428@syzkaller.appspotmail.com
> > Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
> > ---
> > 
> > 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@anirudhrb.com/
> > 
> > ---
> >   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.

Well, this doesn't read or modify the contents of unlink_rx and unlink_tx.
So, it looks safe to me. Let me know if I'm missing something here.

> 
> >   	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?

I added these wrappers purely for convenience. There is no other purpose.
Would you prefer this patch without the wrappers?

Thanks for the review!

	- Anirudh.

Re: [PATCH v2] usbip: give back URBs for unsent unlink requests during cleanup

[Anirudh Rayabharam]

On Tue, Aug 10, 2021 at 05:25:51PM -0600, Shuah Khan wrote:
> 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.

Sure, I will make it a two patch series where the first one fixes the
problem and the second one does the refactor.

> 
> > [1]: https://syzkaller.appspot.com/bug?id=08f12df95ae7da69814e64eb5515d5a85ed06b76
> > 
> > Reported-by: syzbot+74d6ef051d3d2eacf428@syzkaller.appspotmail.com
> > Tested-by: syzbot+74d6ef051d3d2eacf428@syzkaller.appspotmail.com
> > Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
> > ---
> > 
> > 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@anirudhrb.com/
> > 
> > ---
> >   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.

Well, this doesn't read or modify the contents of unlink_rx and unlink_tx.
So, it looks safe to me. Let me know if I'm missing something here.

> 
> >   	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?

I added these wrappers purely for convenience. There is no other purpose.
Would you prefer this patch without the wrappers?

Thanks for the review!

	- Anirudh.
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Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees

Re: [PATCH v2] usbip: give back URBs for unsent unlink requests during cleanup

[Shuah Khan]

On 8/11/21 7:58 AM, Anirudh Rayabharam wrote:
> On Tue, Aug 10, 2021 at 05:25:51PM -0600, Shuah Khan wrote:
>> 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.
> 
> Sure, I will make it a two patch series where the first one fixes the
> problem and the second one does the refactor.
> 
>>
>>> [1]: https://syzkaller.appspot.com/bug?id=08f12df95ae7da69814e64eb5515d5a85ed06b76
>>>
>>> Reported-by: syzbot+74d6ef051d3d2eacf428@syzkaller.appspotmail.com
>>> Tested-by: syzbot+74d6ef051d3d2eacf428@syzkaller.appspotmail.com
>>> Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
>>> ---
>>>
>>> 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@anirudhrb.com/
>>>
>>> ---
>>>    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.
> 
> Well, this doesn't read or modify the contents of unlink_rx and unlink_tx.
> So, it looks safe to me. Let me know if I'm missing something here.
> 
>>
>>>    	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?
> 
> I added these wrappers purely for convenience. There is no other purpose.
> Would you prefer this patch without the wrappers?
> 

Yes. Prefer it without the wrappers. When you take the wrappers
out, I think the unlink_rx could be within spinlock hold easily.

thanks,
-- Shuah

Re: [PATCH v2] usbip: give back URBs for unsent unlink requests during cleanup

[Shuah Khan]

On 8/11/21 7:58 AM, Anirudh Rayabharam wrote:
> On Tue, Aug 10, 2021 at 05:25:51PM -0600, Shuah Khan wrote:
>> 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.
> 
> Sure, I will make it a two patch series where the first one fixes the
> problem and the second one does the refactor.
> 
>>
>>> [1]: https://syzkaller.appspot.com/bug?id=08f12df95ae7da69814e64eb5515d5a85ed06b76
>>>
>>> Reported-by: syzbot+74d6ef051d3d2eacf428@syzkaller.appspotmail.com
>>> Tested-by: syzbot+74d6ef051d3d2eacf428@syzkaller.appspotmail.com
>>> Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
>>> ---
>>>
>>> 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@anirudhrb.com/
>>>
>>> ---
>>>    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.
> 
> Well, this doesn't read or modify the contents of unlink_rx and unlink_tx.
> So, it looks safe to me. Let me know if I'm missing something here.
> 
>>
>>>    	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?
> 
> I added these wrappers purely for convenience. There is no other purpose.
> Would you prefer this patch without the wrappers?
> 

Yes. Prefer it without the wrappers. When you take the wrappers
out, I think the unlink_rx could be within spinlock hold easily.

thanks,
-- Shuah
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