xen/netback: don't call kfree_skb() with interrupts disabled

It is not allowed to call kfree_skb() from hardware interrupt
context or with interrupts being disabled. So remove kfree_skb()
from the spin_lock_irqsave() section and use the already existing
"drop" label in xenvif_start_xmit() for dropping the SKB. At the
same time replace the dev_kfree_skb() call there with a call of
dev_kfree_skb_any(), as xenvif_start_xmit() can be called with
disabled interrupts.

This is XSA-424 / CVE-2022-42328 / CVE-2022-42329.

Fixes: be81992f9086 ("xen/netback: don't queue unlimited number of packages")
Reported-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index 1545cbe..3dbfc8a 100644 (file)
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -386,7 +386,7 @@ int xenvif_dealloc_kthread(void *data);
 irqreturn_t xenvif_ctrl_irq_fn(int irq, void *data);
 
 bool xenvif_have_rx_work(struct xenvif_queue *queue, bool test_kthread);
-void xenvif_rx_queue_tail(struct xenvif_queue *queue, struct sk_buff *skb);
+bool xenvif_rx_queue_tail(struct xenvif_queue *queue, struct sk_buff *skb);
 
 void xenvif_carrier_on(struct xenvif *vif);
 

diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index 650fa18..f3f2c07 100644 (file)
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -254,14 +254,16 @@ xenvif_start_xmit(struct sk_buff *skb, struct net_device *dev)
        if (vif->hash.alg == XEN_NETIF_CTRL_HASH_ALGORITHM_NONE)
                skb_clear_hash(skb);
 
-       xenvif_rx_queue_tail(queue, skb);
+       if (!xenvif_rx_queue_tail(queue, skb))
+               goto drop;
+
        xenvif_kick_thread(queue);
 
        return NETDEV_TX_OK;
 
  drop:
        vif->dev->stats.tx_dropped++;
-       dev_kfree_skb(skb);
+       dev_kfree_skb_any(skb);
        return NETDEV_TX_OK;
 }
 

diff --git a/drivers/net/xen-netback/rx.c b/drivers/net/xen-netback/rx.c
index 9327621..0ba754e 100644 (file)
--- a/drivers/net/xen-netback/rx.c
+++ b/drivers/net/xen-netback/rx.c
@@ -82,9 +82,10 @@ static bool xenvif_rx_ring_slots_available(struct xenvif_queue *queue)
        return false;
 }
 
-void xenvif_rx_queue_tail(struct xenvif_queue *queue, struct sk_buff *skb)
+bool xenvif_rx_queue_tail(struct xenvif_queue *queue, struct sk_buff *skb)
 {
        unsigned long flags;
+       bool ret = true;
 
        spin_lock_irqsave(&queue->rx_queue.lock, flags);
 
@@ -92,8 +93,7 @@ void xenvif_rx_queue_tail(struct xenvif_queue *queue, struct sk_buff *skb)
                struct net_device *dev = queue->vif->dev;
 
                netif_tx_stop_queue(netdev_get_tx_queue(dev, queue->id));
-               kfree_skb(skb);
-               queue->vif->dev->stats.rx_dropped++;
+               ret = false;
        } else {
                if (skb_queue_empty(&queue->rx_queue))
                        xenvif_update_needed_slots(queue, skb);
@@ -104,6 +104,8 @@ void xenvif_rx_queue_tail(struct xenvif_queue *queue, struct sk_buff *skb)
        }
 
        spin_unlock_irqrestore(&queue->rx_queue.lock, flags);
+
+       return ret;
 }
 
 static struct sk_buff *xenvif_rx_dequeue(struct xenvif_queue *queue)