xen/netfront: don't cache skb_shinfo()

BugLink: https://bugs.launchpad.net/bugs/1835845
commit d472b3a6cf63cd31cae1ed61930f07e6cd6671b5 upstream.

skb_shinfo() can change when calling __pskb_pull_tail(): Don't cache
its return value.

Cc: stable@vger.kernel.org
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 37c3bf29734e7d0dd32a6267c53015afefab73c7..9d2829fa2a26ad8e6c75a3da085afe08ae268cf5 100644 (file)
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -894,7 +894,6 @@ static RING_IDX xennet_fill_frags(struct netfront_queue *queue,
                                  struct sk_buff *skb,
                                  struct sk_buff_head *list)
 {
-       struct skb_shared_info *shinfo = skb_shinfo(skb);
        RING_IDX cons = queue->rx.rsp_cons;
        struct sk_buff *nskb;
 
@@ -903,15 +902,16 @@ static RING_IDX xennet_fill_frags(struct netfront_queue *queue,
                        RING_GET_RESPONSE(&queue->rx, ++cons);
                skb_frag_t *nfrag = &skb_shinfo(nskb)->frags[0];
 
-               if (shinfo->nr_frags == MAX_SKB_FRAGS) {
+               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));
                        __pskb_pull_tail(skb, pull_to - skb_headlen(skb));
                }
-               BUG_ON(shinfo->nr_frags >= MAX_SKB_FRAGS);
+               BUG_ON(skb_shinfo(skb)->nr_frags >= MAX_SKB_FRAGS);
 
-               skb_add_rx_frag(skb, shinfo->nr_frags, skb_frag_page(nfrag),
+               skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags,
+                               skb_frag_page(nfrag),
                                rx->offset, rx->status, PAGE_SIZE);
 
                skb_shinfo(nskb)->nr_frags = 0;