[PATCH v3 0/2] Fix syzkaller bug: hung task in hub_port_init

This series fixes the hung task bug in hub_port_init reported by
syzkaller at:

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

The first patch in the series fixes the issue and the second patch does
some refactoring to avoid duplicate code.

Changes in v3:
- Split the patch into two patches
- Remove the convenience wrappers as suggested by Shuah
- Remove the WARN as suggested by Greg

Changes in v2:
Use WARN_ON() instead of BUG() when unlink_list is neither unlink_tx nor
unlink_rx.
v2: https://lore.kernel.org/lkml/20210806181335.2078-1-mail@anirudhrb.com/

v1: https://lore.kernel.org/lkml/20210806164015.25263-1-mail@anirudhrb.com/

Anirudh Rayabharam (2):
  usbip: give back URBs for unsent unlink requests during cleanup
  usbip: eliminate duplicate code in vhci_device_unlink_cleanup

 drivers/usb/usbip/vhci_hcd.c | 31 ++++++++++++++++++-------------
 1 file changed, 18 insertions(+), 13 deletions(-)

-- 
2.26.2

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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.

[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 <redacted>
---
 drivers/usb/usbip/vhci_hcd.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
index 4ba6bcdaa8e9..6f3f374d4bbc 100644
--- a/drivers/usb/usbip/vhci_hcd.c
+++ b/drivers/usb/usbip/vhci_hcd.c

@@ -957,8 +957,34 @@ static void vhci_device_unlink_cleanup(struct vhci_device *vdev)
 	spin_lock(&vdev->priv_lock);
 
 	list_for_each_entry_safe(unlink, tmp, &vdev->unlink_tx, list) {
+		struct urb *urb;
+
+		/* give back URB of unsent unlink request */
 		pr_info("unlink cleanup tx %lu\n", unlink->unlink_seqnum);
+
+		urb = pickup_urb_and_free_priv(vdev, unlink->unlink_seqnum);
+		if (!urb) {
+			pr_info("the urb (seqnum %lu) was already given back\n",
+				unlink->unlink_seqnum);
+			list_del(&unlink->list);
+			kfree(unlink);
+			continue;
+		}
+
+		urb->status = -ENODEV;
+
+		usb_hcd_unlink_urb_from_ep(hcd, urb);
+
 		list_del(&unlink->list);
+
+		spin_unlock(&vdev->priv_lock);
+		spin_unlock_irqrestore(&vhci->lock, flags);
+
+		usb_hcd_giveback_urb(hcd, urb, urb->status);
+
+		spin_lock_irqsave(&vhci->lock, flags);
+		spin_lock(&vdev->priv_lock);
+
 		kfree(unlink);
 	}
 

-- 
2.26.2

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The cleanup code for unlink_tx and unlink_rx lists is almost the same.
So, extract it into a new function and call it for both unlink_rx and
unlink_tx.

Signed-off-by: Anirudh Rayabharam <redacted>
---
 drivers/usb/usbip/vhci_hcd.c | 57 ++++++++++++------------------------
 1 file changed, 18 insertions(+), 39 deletions(-)

diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
index 6f3f374d4bbc..b142508b46ce 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);

@@ -956,46 +957,15 @@ static void vhci_device_unlink_cleanup(struct vhci_device *vdev)
 	spin_lock_irqsave(&vhci->lock, flags);
 	spin_lock(&vdev->priv_lock);
 
-	list_for_each_entry_safe(unlink, tmp, &vdev->unlink_tx, list) {
+	list_for_each_entry_safe(unlink, tmp, unlink_list, list) {
 		struct urb *urb;
 
-		/* give back urb of unsent unlink request */
-		pr_info("unlink cleanup tx %lu\n", unlink->unlink_seqnum);
-
-		urb = pickup_urb_and_free_priv(vdev, unlink->unlink_seqnum);
-		if (!urb) {
-			pr_info("the urb (seqnum %lu) was already given back\n",
-				unlink->unlink_seqnum);
-			list_del(&unlink->list);
-			kfree(unlink);
-			continue;
-		}
-
-		urb->status = -ENODEV;
-
-		usb_hcd_unlink_urb_from_ep(hcd, urb);
-
-		list_del(&unlink->list);
-
-		spin_unlock(&vdev->priv_lock);
-		spin_unlock_irqrestore(&vhci->lock, flags);
-
-		usb_hcd_giveback_urb(hcd, urb, urb->status);
-
-		spin_lock_irqsave(&vhci->lock, flags);
-		spin_lock(&vdev->priv_lock);
-
-		kfree(unlink);
-	}
-
-	while (!list_empty(&vdev->unlink_rx)) {
-		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) {

@@ -1027,6 +997,15 @@ static void vhci_device_unlink_cleanup(struct vhci_device *vdev)
 	spin_unlock_irqrestore(&vhci->lock, flags);
 }
 
+static void vhci_device_unlink_cleanup(struct vhci_device *vdev)
+{
+	/* give back URB of unsent unlink request */
+	vhci_cleanup_unlink_list(vdev, &vdev->unlink_tx);
+
+	/* give back URB of unanswered unlink request */
+	vhci_cleanup_unlink_list(vdev, &vdev->unlink_rx);
+}
+
 /*
  * The important thing is that only one context begins cleanup.
  * This is why error handling and cleanup become simple.

-- 
2.26.2

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On 8/13/21 12:25 PM, Anirudh Rayabharam wrote:

I know this is an exiting one.
Let's make this pr_debug or remove it all together.

Let's make this pr_debug or remove it all together.

thanks,
-- Shuah
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On Tue, Aug 17, 2021 at 05:16:51PM -0600, Shuah Khan wrote:

On 8/13/21 12:25 PM, Anirudh Rayabharam wrote:

quoted

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.

[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 <redacted>
---
  drivers/usb/usbip/vhci_hcd.c | 26 ++++++++++++++++++++++++++
  1 file changed, 26 insertions(+)

diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
index 4ba6bcdaa8e9..6f3f374d4bbc 100644
--- a/drivers/usb/usbip/vhci_hcd.c
+++ b/drivers/usb/usbip/vhci_hcd.c

@@ -957,8 +957,34 @@ static void vhci_device_unlink_cleanup(struct vhci_device *vdev)
  	spin_lock(&vdev->priv_lock);
  	list_for_each_entry_safe(unlink, tmp, &vdev->unlink_tx, list) {
+		struct urb *urb;
+
+		/* give back URB of unsent unlink request */
  		pr_info("unlink cleanup tx %lu\n", unlink->unlink_seqnum);

I know this is an exiting one.
Let's make this pr_debug or remove it all together.

quoted

+
+		urb = pickup_urb_and_free_priv(vdev, unlink->unlink_seqnum);
+		if (!urb) {
+			pr_info("the urb (seqnum %lu) was already given back\n",
+				unlink->unlink_seqnum);

Let's make this pr_debug or remove it all together.

As you have a struct device for all of these, please use dev_dbg() and
friends, not pr_*(), for all of these.

thanks,

greg k-h
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On 8/17/21 11:39 PM, Greg KH wrote:

On Tue, Aug 17, 2021 at 05:16:51PM -0600, Shuah Khan wrote:

quoted

On 8/13/21 12:25 PM, Anirudh Rayabharam wrote:

quoted

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.

[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 <redacted>
---
   drivers/usb/usbip/vhci_hcd.c | 26 ++++++++++++++++++++++++++
   1 file changed, 26 insertions(+)

diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
index 4ba6bcdaa8e9..6f3f374d4bbc 100644
--- a/drivers/usb/usbip/vhci_hcd.c
+++ b/drivers/usb/usbip/vhci_hcd.c

@@ -957,8 +957,34 @@ static void vhci_device_unlink_cleanup(struct vhci_device *vdev)
   	spin_lock(&vdev->priv_lock);
   	list_for_each_entry_safe(unlink, tmp, &vdev->unlink_tx, list) {
+		struct urb *urb;
+
+		/* give back URB of unsent unlink request */
   		pr_info("unlink cleanup tx %lu\n", unlink->unlink_seqnum);

I know this is an exiting one.
Let's make this pr_debug or remove it all together.

quoted

+
+		urb = pickup_urb_and_free_priv(vdev, unlink->unlink_seqnum);
+		if (!urb) {
+			pr_info("the urb (seqnum %lu) was already given back\n",
+				unlink->unlink_seqnum);

Let's make this pr_debug or remove it all together.

As you have a struct device for all of these, please use dev_dbg() and
friends, not pr_*(), for all of these.

Yes. Makes perfect sense.

thanks,
-- Shuah
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On Wed, Aug 18, 2021 at 12:36:11PM -0600, Shuah Khan wrote:

On 8/17/21 11:39 PM, Greg KH wrote:

quoted

On Tue, Aug 17, 2021 at 05:16:51PM -0600, Shuah Khan wrote:

quoted

On 8/13/21 12:25 PM, Anirudh Rayabharam wrote:

quoted

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.

[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 <redacted>
---
   drivers/usb/usbip/vhci_hcd.c | 26 ++++++++++++++++++++++++++
   1 file changed, 26 insertions(+)

diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
index 4ba6bcdaa8e9..6f3f374d4bbc 100644
--- a/drivers/usb/usbip/vhci_hcd.c
+++ b/drivers/usb/usbip/vhci_hcd.c

@@ -957,8 +957,34 @@ static void vhci_device_unlink_cleanup(struct vhci_device *vdev)
   	spin_lock(&vdev->priv_lock);
   	list_for_each_entry_safe(unlink, tmp, &vdev->unlink_tx, list) {
+		struct urb *urb;
+
+		/* give back URB of unsent unlink request */
   		pr_info("unlink cleanup tx %lu\n", unlink->unlink_seqnum);

I know this is an exiting one.
Let's make this pr_debug or remove it all together.

quoted

+
+		urb = pickup_urb_and_free_priv(vdev, unlink->unlink_seqnum);
+		if (!urb) {
+			pr_info("the urb (seqnum %lu) was already given back\n",
+				unlink->unlink_seqnum);

Let's make this pr_debug or remove it all together.

As you have a struct device for all of these, please use dev_dbg() and
friends, not pr_*(), for all of these.

Yes. Makes perfect sense.

Perhaps we should use usbip_dbg_vhci_hc() instead of dev_dbg()? It is
one of the custom macros defined by the usbip driver for printing debug
logs.

Thanks,

	Anirudh
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On 8/19/21 12:09 PM, Anirudh Rayabharam wrote:

On Wed, Aug 18, 2021 at 12:36:11PM -0600, Shuah Khan wrote:

quoted

On 8/17/21 11:39 PM, Greg KH wrote:

quoted

On Tue, Aug 17, 2021 at 05:16:51PM -0600, Shuah Khan wrote:

quoted

On 8/13/21 12:25 PM, Anirudh Rayabharam wrote:

quoted

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.

[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 <redacted>
---
    drivers/usb/usbip/vhci_hcd.c | 26 ++++++++++++++++++++++++++
    1 file changed, 26 insertions(+)

diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
index 4ba6bcdaa8e9..6f3f374d4bbc 100644
--- a/drivers/usb/usbip/vhci_hcd.c
+++ b/drivers/usb/usbip/vhci_hcd.c

@@ -957,8 +957,34 @@ static void vhci_device_unlink_cleanup(struct vhci_device *vdev)
    	spin_lock(&vdev->priv_lock);
    	list_for_each_entry_safe(unlink, tmp, &vdev->unlink_tx, list) {
+		struct urb *urb;
+
+		/* give back URB of unsent unlink request */
    		pr_info("unlink cleanup tx %lu\n", unlink->unlink_seqnum);

I know this is an exiting one.
Let's make this pr_debug or remove it all together.

quoted

+
+		urb = pickup_urb_and_free_priv(vdev, unlink->unlink_seqnum);
+		if (!urb) {
+			pr_info("the urb (seqnum %lu) was already given back\n",
+				unlink->unlink_seqnum);

Let's make this pr_debug or remove it all together.

As you have a struct device for all of these, please use dev_dbg() and
friends, not pr_*(), for all of these.

Yes. Makes perfect sense.

Perhaps we should use usbip_dbg_vhci_hc() instead of dev_dbg()? It is
one of the custom macros defined by the usbip driver for printing debug
logs.

Yes that macro could be used. However, let's just get rid of the messages.
I don't see much use for them.

thanks,
-- Shuah
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