[PATCH v3 0/1] usbnet:fix NPE during rx_complete

[PATCH v3 0/1] usbnet:fix NPE during rx_complete

[Ying Lu]

From: Ying Lu <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.


Changes in v3
-use the correct "Fixes:" tag format.

Changes in v2
-Use the formal name instead of an email alias.

Ying Lu (1):
  usbnet:fix NPE during rx_complete

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

-- 
2.49.0

[PATCH v3 1/1] usbnet:fix NPE during rx_complete

[Ying Lu]

From: Ying Lu <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).

Fixes: 04e906839a05 ("usbnet: fix cyclical race on disconnect with work queue")
Signed-off-by: Ying Lu <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");
-- 
2.49.0

Re: [PATCH v3 1/1] usbnet:fix NPE during rx_complete

[Greg KH]

On Wed, Apr 02, 2025 at 04:06:29PM +0800, Ying Lu wrote:
> From: Ying Lu <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).
> 
> Fixes: 04e906839a05 ("usbnet: fix cyclical race on disconnect with work queue")
> Signed-off-by: Ying Lu <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");
> -- 
> 2.49.0
> 
> 

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
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  this.

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