af-packet: fix - avoid reading stale data

Currently we flush tp_status and then flush the remainder of the header+payload.
tp_status should be flushed in the end to avoid stale data being read by user-space.

Incorrectly re-ordered barriers in v1.

Signed-off-by: Chetan Loke <loke.chetan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 1 deletions

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index d2294ad1a895..c698cec0a445 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1129,7 +1129,6 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
         else
                 sll->sll_ifindex = dev->ifindex;
 
-        __packet_set_status(po, h.raw, status);
         smp_mb();
 #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE == 1
         {
@@ -1138,8 +1137,10 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
                 end = (u8 *)PAGE_ALIGN((unsigned long)h.raw + macoff + snaplen);
                 for (start = h.raw; start < end; start += PAGE_SIZE)
                         flush_dcache_page(pgv_to_page(start));
+                smp_wmb();
         }
 #endif
+        __packet_set_status(po, h.raw, status);
 
         sk->sk_data_ready(sk, 0);