[PATCH v1 0/1] usbnet:fix NPE during rx_complete

[PATCH v1 0/1] usbnet:fix NPE during rx_complete

[Ying Lu]

From: luying1 <luying1@xiaomi.com>

The patchset fix the issue caused by the following modifications:
commit 04e906839a053f092ef53f4fb2d610983412b904
(usbnet: fix cyclical race on disconnect with work queue)

The issue:
The usb_submit_urb function lacks a usbnet_going_away validation,
whereas __usbnet_queue_skb includes this check. This inconsistency
creates a race condition where: A URB request may succeed, but
the corresponding SKB data fails to be queued.

Subsequent processes (e.g., rx_complete → defer_bh → __skb_unlink(skb, list))
attempt to access skb->next, triggering a NULL pointer dereference (Kernel Panic).

Fix issue:
adding the usbnet_going_away check in usb_submit_urb to synchronize the validation logic.


luying1 (1):
  usbnet:fix NPE during rx_complete

 drivers/net/usb/usbnet.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

-- 
2.40.1

[PATCH v1 1/1] usbnet:fix NPE during rx_complete

[Ying Lu]

From: luying1 <luying1@xiaomi.com>

Missing usbnet_going_away Check in Critical Path.
The usb_submit_urb function lacks a usbnet_going_away
validation, whereas __usbnet_queue_skb includes this check.

This inconsistency creates a race condition where:
A URB request may succeed, but the corresponding SKB data
fails to be queued.

Subsequent processes:
(e.g., rx_complete → defer_bh → __skb_unlink(skb, list))
attempt to access skb->next, triggering a NULL pointer
dereference (Kernel Panic).

Signed-off-by: luying1 <luying1@xiaomi.com>
---
 drivers/net/usb/usbnet.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index 44179f4e807f..5161bb5d824b 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -519,7 +519,8 @@ static int rx_submit (struct usbnet *dev, struct urb *urb, gfp_t flags)
 	    netif_device_present (dev->net) &&
 	    test_bit(EVENT_DEV_OPEN, &dev->flags) &&
 	    !test_bit (EVENT_RX_HALT, &dev->flags) &&
-	    !test_bit (EVENT_DEV_ASLEEP, &dev->flags)) {
+	    !test_bit (EVENT_DEV_ASLEEP, &dev->flags) &&
+	    !usbnet_going_away(dev)) {
 		switch (retval = usb_submit_urb (urb, GFP_ATOMIC)) {
 		case -EPIPE:
 			usbnet_defer_kevent (dev, EVENT_RX_HALT);
@@ -540,8 +541,7 @@ static int rx_submit (struct usbnet *dev, struct urb *urb, gfp_t flags)
 			tasklet_schedule (&dev->bh);
 			break;
 		case 0:
-			if (!usbnet_going_away(dev))
-				__usbnet_queue_skb(&dev->rxq, skb, rx_start);
+			__usbnet_queue_skb(&dev->rxq, skb, rx_start);
 		}
 	} else {
 		netif_dbg(dev, ifdown, dev->net, "rx: stopped\n");
-- 
2.40.1

Re: [PATCH v1 1/1] usbnet:fix NPE during rx_complete

[Greg KH]

On Tue, Apr 01, 2025 at 06:18:01PM +0800, Ying Lu wrote:
> From: luying1 <luying1@xiaomi.com>
> 
> Missing usbnet_going_away Check in Critical Path.
> The usb_submit_urb function lacks a usbnet_going_away
> validation, whereas __usbnet_queue_skb includes this check.
> 
> This inconsistency creates a race condition where:
> A URB request may succeed, but the corresponding SKB data
> fails to be queued.
> 
> Subsequent processes:
> (e.g., rx_complete → defer_bh → __skb_unlink(skb, list))
> attempt to access skb->next, triggering a NULL pointer
> dereference (Kernel Panic).
> 
> Signed-off-by: luying1 <luying1@xiaomi.com>

Please use your name, not an email alias.

Also, what commit id does this fix?  Should it be applied to stable
kernels?

thanks,

greg k-h

Re: [PATCH v1 1/1] usbnet:fix NPE during rx_complete

[Ying Lu]

On Tue, Apr 1, 2025 at 6:31 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Tue, Apr 01, 2025 at 06:18:01PM +0800, Ying Lu wrote:
> > From: luying1 <luying1@xiaomi.com>
> >
> > Missing usbnet_going_away Check in Critical Path.
> > The usb_submit_urb function lacks a usbnet_going_away
> > validation, whereas __usbnet_queue_skb includes this check.
> >
> > This inconsistency creates a race condition where:
> > A URB request may succeed, but the corresponding SKB data
> > fails to be queued.
> >
> > Subsequent processes:
> > (e.g., rx_complete → defer_bh → __skb_unlink(skb, list))
> > attempt to access skb->next, triggering a NULL pointer
> > dereference (Kernel Panic).
> >
> > Signed-off-by: luying1 <luying1@xiaomi.com>
>
> Please use your name, not an email alias.
>
OK, I have updated. please check the Patch v2

> Also, what commit id does this fix?  Should it be applied to stable
> kernels?
The commit  id is 04e906839a053f092ef53f4fb2d610983412b904
(usbnet: fix cyclical race on disconnect with work queue)
Should it be applied to stable kernels?  -- Yes

> thanks,
>
> greg k-h

Re: [PATCH v1 1/1] usbnet:fix NPE during rx_complete

[Greg KH]

On Tue, Apr 01, 2025 at 08:48:01PM +0800, Ying Lu wrote:
> On Tue, Apr 1, 2025 at 6:31 PM Greg KH <gregkh@linuxfoundation.org> wrote:
> >
> > On Tue, Apr 01, 2025 at 06:18:01PM +0800, Ying Lu wrote:
> > > From: luying1 <luying1@xiaomi.com>
> > >
> > > Missing usbnet_going_away Check in Critical Path.
> > > The usb_submit_urb function lacks a usbnet_going_away
> > > validation, whereas __usbnet_queue_skb includes this check.
> > >
> > > This inconsistency creates a race condition where:
> > > A URB request may succeed, but the corresponding SKB data
> > > fails to be queued.
> > >
> > > Subsequent processes:
> > > (e.g., rx_complete → defer_bh → __skb_unlink(skb, list))
> > > attempt to access skb->next, triggering a NULL pointer
> > > dereference (Kernel Panic).
> > >
> > > Signed-off-by: luying1 <luying1@xiaomi.com>
> >
> > Please use your name, not an email alias.
> >
> OK, I have updated. please check the Patch v2
> 
> > Also, what commit id does this fix?  Should it be applied to stable
> > kernels?
> The commit  id is 04e906839a053f092ef53f4fb2d610983412b904
> (usbnet: fix cyclical race on disconnect with work queue)
> Should it be applied to stable kernels?  -- Yes

Please mark the commit with that information, you seem to have not done
so for the v2 version :(

Re: [PATCH v1 1/1] usbnet:fix NPE during rx_complete

[Ying Lu]

On Tue, Apr 1, 2025 at 9:48 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Tue, Apr 01, 2025 at 08:48:01PM +0800, Ying Lu wrote:
> > On Tue, Apr 1, 2025 at 6:31 PM Greg KH <gregkh@linuxfoundation.org> wrote:
> > >
> > > On Tue, Apr 01, 2025 at 06:18:01PM +0800, Ying Lu wrote:
> > > > From: luying1 <luying1@xiaomi.com>
> > > >
> > > > Missing usbnet_going_away Check in Critical Path.
> > > > The usb_submit_urb function lacks a usbnet_going_away
> > > > validation, whereas __usbnet_queue_skb includes this check.
> > > >
> > > > This inconsistency creates a race condition where:
> > > > A URB request may succeed, but the corresponding SKB data
> > > > fails to be queued.
> > > >
> > > > Subsequent processes:
> > > > (e.g., rx_complete → defer_bh → __skb_unlink(skb, list))
> > > > attempt to access skb->next, triggering a NULL pointer
> > > > dereference (Kernel Panic).
> > > >
> > > > Signed-off-by: luying1 <luying1@xiaomi.com>
> > >
> > > Please use your name, not an email alias.
> > >
> > OK, I have updated. please check the Patch v2
> >
> > > Also, what commit id does this fix?  Should it be applied to stable
> > > kernels?
> > The commit  id is 04e906839a053f092ef53f4fb2d610983412b904
> > (usbnet: fix cyclical race on disconnect with work queue)
> > Should it be applied to stable kernels?  -- Yes
>
> Please mark the commit with that information, you seem to have not done
> so for the v2 version :(
Thank you for your response. Could you please confirm if I understand correctly:
Should we include in our commit message which commit id we're fixing?

Re: [PATCH v1 1/1] usbnet:fix NPE during rx_complete

[Greg KH]

On Wed, Apr 02, 2025 at 08:12:06AM +0800, Ying Lu wrote:
> On Tue, Apr 1, 2025 at 9:48 PM Greg KH <gregkh@linuxfoundation.org> wrote:
> >
> > On Tue, Apr 01, 2025 at 08:48:01PM +0800, Ying Lu wrote:
> > > On Tue, Apr 1, 2025 at 6:31 PM Greg KH <gregkh@linuxfoundation.org> wrote:
> > > >
> > > > On Tue, Apr 01, 2025 at 06:18:01PM +0800, Ying Lu wrote:
> > > > > From: luying1 <luying1@xiaomi.com>
> > > > >
> > > > > Missing usbnet_going_away Check in Critical Path.
> > > > > The usb_submit_urb function lacks a usbnet_going_away
> > > > > validation, whereas __usbnet_queue_skb includes this check.
> > > > >
> > > > > This inconsistency creates a race condition where:
> > > > > A URB request may succeed, but the corresponding SKB data
> > > > > fails to be queued.
> > > > >
> > > > > Subsequent processes:
> > > > > (e.g., rx_complete → defer_bh → __skb_unlink(skb, list))
> > > > > attempt to access skb->next, triggering a NULL pointer
> > > > > dereference (Kernel Panic).
> > > > >
> > > > > Signed-off-by: luying1 <luying1@xiaomi.com>
> > > >
> > > > Please use your name, not an email alias.
> > > >
> > > OK, I have updated. please check the Patch v2
> > >
> > > > Also, what commit id does this fix?  Should it be applied to stable
> > > > kernels?
> > > The commit  id is 04e906839a053f092ef53f4fb2d610983412b904
> > > (usbnet: fix cyclical race on disconnect with work queue)
> > > Should it be applied to stable kernels?  -- Yes
> >
> > Please mark the commit with that information, you seem to have not done
> > so for the v2 version :(
> Thank you for your response. Could you please confirm if I understand correctly:
> Should we include in our commit message which commit id we're fixing?

No, use the correct "Fixes:" tag format as described in the
documentation.

thanks,

greg k-h

Re: [PATCH v1 1/1] usbnet:fix NPE during rx_complete

[Ying Lu]

On Wed, Apr 2, 2025 at 3:12 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Wed, Apr 02, 2025 at 08:12:06AM +0800, Ying Lu wrote:
> > On Tue, Apr 1, 2025 at 9:48 PM Greg KH <gregkh@linuxfoundation.org> wrote:
> > >
> > > On Tue, Apr 01, 2025 at 08:48:01PM +0800, Ying Lu wrote:
> > > > On Tue, Apr 1, 2025 at 6:31 PM Greg KH <gregkh@linuxfoundation.org> wrote:
> > > > >
> > > > > On Tue, Apr 01, 2025 at 06:18:01PM +0800, Ying Lu wrote:
> > > > > > From: luying1 <luying1@xiaomi.com>
> > > > > >
> > > > > > Missing usbnet_going_away Check in Critical Path.
> > > > > > The usb_submit_urb function lacks a usbnet_going_away
> > > > > > validation, whereas __usbnet_queue_skb includes this check.
> > > > > >
> > > > > > This inconsistency creates a race condition where:
> > > > > > A URB request may succeed, but the corresponding SKB data
> > > > > > fails to be queued.
> > > > > >
> > > > > > Subsequent processes:
> > > > > > (e.g., rx_complete → defer_bh → __skb_unlink(skb, list))
> > > > > > attempt to access skb->next, triggering a NULL pointer
> > > > > > dereference (Kernel Panic).
> > > > > >
> > > > > > Signed-off-by: luying1 <luying1@xiaomi.com>
> > > > >
> > > > > Please use your name, not an email alias.
> > > > >
> > > > OK, I have updated. please check the Patch v2
> > > >
> > > > > Also, what commit id does this fix?  Should it be applied to stable
> > > > > kernels?
> > > > The commit  id is 04e906839a053f092ef53f4fb2d610983412b904
> > > > (usbnet: fix cyclical race on disconnect with work queue)
> > > > Should it be applied to stable kernels?  -- Yes
> > >
> > > Please mark the commit with that information, you seem to have not done
> > > so for the v2 version :(
> > Thank you for your response. Could you please confirm if I understand correctly:
> > Should we include in our commit message which commit id we're fixing?
>
> No, use the correct "Fixes:" tag format as described in the
> documentation.
>
> thanks,
>
> greg k-h

Oh, I see. Thank you very much for the reminder!
I've already fixed it in the PATCH v3. Could you please take another look?

Thanks,

Ying Lu