linux-kernel - [PATCH net-next 04/12] tap: fix use-after-free

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Message-ID: <1516923320-16959-5-git-send-email-mst@redhat.com>
Date:   Fri, 26 Jan 2018 01:36:31 +0200
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     netdev@...r.kernel.org, Jason Wang <jasowang@...hat.com>,
        John Fastabend <john.fastabend@...il.com>,
        David Miller <davem@...emloft.net>
Subject: [PATCH net-next 04/12] 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@...hat.com>
---
 drivers/net/tap.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/net/tap.c b/drivers/net/tap.c
index 7c38659..7787269 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
-- 
MST