We need to drop the refcnt of page when we fail to allocate an skb for frag
list, otherwise it will be leaked. The bug was introduced by commit
2613af0ed18a11d5c566a81f9a6510b73180660a ("virtio_net: migrate mergeable rx
buffers to page frag allocators").

Cc: Michael Dalton <mwdal...@google.com>
Cc: Eric Dumazet <eduma...@google.com>
Cc: Rusty Russell <ru...@rustcorp.com.au>
Cc: Michael S. Tsirkin <m...@redhat.com>
Signed-off-by: Jason Wang <jasow...@redhat.com>
---
The patch was needed for 3.12 stable.
---
 drivers/net/virtio_net.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 69ad42b..3798517 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -322,9 +322,11 @@ static int receive_mergeable(struct receive_queue *rq, 
struct sk_buff *head_skb)
                                 head_skb->dev->name);
                        len = MERGE_BUFFER_LEN;
                }
+               page = virt_to_head_page(buf);
                if (unlikely(num_skb_frags == MAX_SKB_FRAGS)) {
                        struct sk_buff *nskb = alloc_skb(0, GFP_ATOMIC);
                        if (unlikely(!nskb)) {
+                               put_page(page);
                                head_skb->dev->stats.rx_dropped++;
                                return -ENOMEM;
                        }
@@ -341,7 +343,6 @@ static int receive_mergeable(struct receive_queue *rq, 
struct sk_buff *head_skb)
                        head_skb->len += len;
                        head_skb->truesize += MERGE_BUFFER_LEN;
                }
-               page = virt_to_head_page(buf);
                offset = buf - (char *)page_address(page);
                if (skb_can_coalesce(curr_skb, num_skb_frags, page, offset)) {
                        put_page(page);
-- 
1.8.3.2

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