From: Juergen Gross <jgross@suse.com>
Date: Tue, 18 Dec 2018 15:06:19 +0000 (+0100)
Subject: xen/netfront: tolerate frags with no data
X-Git-Tag: v4.9.149~47
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=ba0b3c189365d3f55b6b633d40ceaa815eb0323d;p=platform%2Fkernel%2Flinux-amlogic.git

xen/netfront: tolerate frags with no data

[ Upstream commit d81c5054a5d1d4999c7cdead7636b6cd4af83d36 ]

At least old Xen net backends seem to send frags with no real data
sometimes. In case such a fragment happens to occur with the frag limit
already reached the frontend will BUG currently even if this situation
is easily recoverable.

Modify the BUG_ON() condition accordingly.

Tested-by: Dietmar Hahn <dietmar.hahn@ts.fujitsu.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index aceae791baf3..14ceeaaa7fe5 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -903,7 +903,7 @@ static RING_IDX xennet_fill_frags(struct netfront_queue *queue,
 		if (skb_shinfo(skb)->nr_frags == MAX_SKB_FRAGS) {
 			unsigned int pull_to = NETFRONT_SKB_CB(skb)->pull_to;
 
-			BUG_ON(pull_to <= skb_headlen(skb));
+			BUG_ON(pull_to < skb_headlen(skb));
 			__pskb_pull_tail(skb, pull_to - skb_headlen(skb));
 		}
 		if (unlikely(skb_shinfo(skb)->nr_frags >= MAX_SKB_FRAGS)) {