From: Michael S. Tsirkin <mst@redhat.com>
Date: Thu, 25 Jan 2018 23:36:31 +0000 (+0200)
Subject: tap: fix use-after-free
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=88fae87327a2261cf8db078f6ce4e5a3e55b30b1;p=openwrt%2Fstaging%2Fblogic.git

tap: fix use-after-free

Lockless access to __ptr_ring_full is only legal if ring is
never resized, otherwise it might cause use-after free errors.
Simply drop the lockless test, we'll drop the packet
a bit later when produce fails.

Fixes: 362899b8 ("macvtap: switch to use skb array")
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/drivers/net/tap.c b/drivers/net/tap.c
index 7c38659b2a76..77872699c45d 100644
--- a/drivers/net/tap.c
+++ b/drivers/net/tap.c
@@ -330,9 +330,6 @@ rx_handler_result_t tap_handle_frame(struct sk_buff **pskb)
 	if (!q)
 		return RX_HANDLER_PASS;
 
-	if (__ptr_ring_full(&q->ring))
-		goto drop;
-
 	skb_push(skb, ETH_HLEN);
 
 	/* Apply the forward feature mask so that we perform segmentation