i40e/i40evf: proper update of the page_offset field

In f8b45b74 ("i40e/i40evf: Use build_skb to build frames")
i40e_build_skb updates the page_offset field with an incorrect offset,
which can lead to data corruption. This patch updates page_offset
correctly, by properly setting truesize.

Note that the bug only appears on architectures where PAGE_SIZE is
8192 or larger.

Fixes: f8b45b74 ("i40e/i40evf: Use build_skb to build frames")
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Acked-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/i40e/i40e_txrx.c

@@ -1854,7 +1854,8 @@ static struct sk_buff *i40e_build_skb(struct i40e_ring *rx_ring,
 #if (PAGE_SIZE < 8192)
 	unsigned int truesize = i40e_rx_pg_size(rx_ring) / 2;
 #else
-	unsigned int truesize = SKB_DATA_ALIGN(size);
+	unsigned int truesize = SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) +
+				SKB_DATA_ALIGN(I40E_SKB_PAD + size);
 #endif
 	struct sk_buff *skb;
 

drivers/net/ethernet/intel/i40evf/i40e_txrx.c

@@ -1190,7 +1190,8 @@ static struct sk_buff *i40e_build_skb(struct i40e_ring *rx_ring,
 #if (PAGE_SIZE < 8192)
 	unsigned int truesize = i40e_rx_pg_size(rx_ring) / 2;
 #else
-	unsigned int truesize = SKB_DATA_ALIGN(size);
+	unsigned int truesize = SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) +
+				SKB_DATA_ALIGN(I40E_SKB_PAD + size);
 #endif
 	struct sk_buff *skb;