From bd1468048aa3e2af865da92990539946d4483989 Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@suse.com>
Date: Tue, 11 Sep 2018 09:04:48 +0200
Subject: [PATCH] xen/netfront: don't bug in case of too many frags
commit ad4f15dc2c70b1de5e0a64d27335962fbc9cf71c upstream.
Commit 57f230ab04d291 ("xen/netfront: raise max number of slots in
xennet_get_responses()") raised the max number of allowed slots by one.
This seems to be problematic in some configurations with netback using
a larger MAX_SKB_FRAGS value (e.g. old Linux kernel with MAX_SKB_FRAGS
defined as 18 instead of nowadays 17).
Instead of BUG_ON() in this case just fall back to retransmission.
Fixes: 57f230ab04d291 ("xen/netfront: raise max number of slots in xennet_get_responses()")
Cc: stable@vger.kernel.org
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>
---
drivers/net/xen-netfront.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 3270b4333668..0a4bd73caae5 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -892,7 +892,11 @@ static RING_IDX xennet_fill_frags(struct netfront_queue *queue,
BUG_ON(pull_to <= skb_headlen(skb));
__pskb_pull_tail(skb, pull_to - skb_headlen(skb));
}
- BUG_ON(skb_shinfo(skb)->nr_frags >= MAX_SKB_FRAGS);
+ if (unlikely(skb_shinfo(skb)->nr_frags >= MAX_SKB_FRAGS)) {
+ queue->rx.rsp_cons = ++cons;
+ kfree_skb(nskb);
+ return ~0U;
+ }
skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags,
skb_frag_page(nfrag),
@@ -1029,6 +1033,8 @@ err:
skb->len += rx->status;
i = xennet_fill_frags(queue, skb, &tmpq);
+ if (unlikely(i == ~0U))
+ goto err;
if (rx->flags & XEN_NETRXF_csum_blank)
skb->ip_summed = CHECKSUM_PARTIAL;