netdev - [PATCH] xen/netback: avoid race in xenvif_rx_ring_slots

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Date:   Tue,  2 Feb 2021 08:09:38 +0100
From:   Juergen Gross <jgross@...e.com>
To:     xen-devel@...ts.xenproject.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Juergen Gross <jgross@...e.com>, Wei Liu <wei.liu@...nel.org>,
        Paul Durrant <paul@....org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Igor Druzhinin <igor.druzhinin@...rix.com>,
        stable@...r.kernel.org
Subject: [PATCH] xen/netback: avoid race in xenvif_rx_ring_slots_available()

Since commit 23025393dbeb3b8b3 ("xen/netback: use lateeoi irq binding")
xenvif_rx_ring_slots_available() is no longer called only from the rx
queue kernel thread, so it needs to access the rx queue with the
associated queue held.

Reported-by: Igor Druzhinin <igor.druzhinin@...rix.com>
Fixes: 23025393dbeb3b8b3 ("xen/netback: use lateeoi irq binding")
Cc: stable@...r.kernel.org
Signed-off-by: Juergen Gross <jgross@...e.com>
---
 drivers/net/xen-netback/rx.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/net/xen-netback/rx.c b/drivers/net/xen-netback/rx.c
index b8febe1d1bfd..accc991d153f 100644
--- a/drivers/net/xen-netback/rx.c
+++ b/drivers/net/xen-netback/rx.c
@@ -38,10 +38,15 @@ static bool xenvif_rx_ring_slots_available(struct xenvif_queue *queue)
 	RING_IDX prod, cons;
 	struct sk_buff *skb;
 	int needed;
+	unsigned long flags;
+
+	spin_lock_irqsave(&queue->rx_queue.lock, flags);
 
 	skb = skb_peek(&queue->rx_queue);
-	if (!skb)
+	if (!skb) {
+		spin_unlock_irqrestore(&queue->rx_queue.lock, flags);
 		return false;
+	}
 
 	needed = DIV_ROUND_UP(skb->len, XEN_PAGE_SIZE);
 	if (skb_is_gso(skb))
@@ -49,6 +54,8 @@ static bool xenvif_rx_ring_slots_available(struct xenvif_queue *queue)
 	if (skb->sw_hash)
 		needed++;
 
+	spin_unlock_irqrestore(&queue->rx_queue.lock, flags);
+
 	do {
 		prod = queue->rx.sring->req_prod;
 		cons = queue->rx.req_cons;
-- 
2.26.2