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 --- 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 9407acbd19a9..f17f602e6171 100644 --- a/drivers/net/xen-netfront.c +++ b/drivers/net/xen-netfront.c @@ -908,7 +908,11 @@ 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), @@ -1045,6 +1049,8 @@ static int xennet_poll(struct napi_struct *napi, int budget) 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;